Reinventing the Tape Dipole
Created by Ulrich H. Steinberg, DJ8GO on 2007-06-28"Editor's Note: Due to the popularity of some of eHam's older articles, many of which you may not have read, the eHam.net team has decided to rerun some of the best articles that we have received since eHam's inception. These articles will be reprinted to add to the quality of eHam's content and in a show of appreciation to the authors of these articles."
Re-inventing the tape dipole
About 20 years ago I traveled with a Heathkit HW-8 and a Hy-Gain TD-1 tape dipole in my bag, and both saw quite a few exotic locales. The QRP transceiver by now is an Elecraft K1, and like the HW-8 the tape dipole was sold somewhere along the way. I normally use a MP-1 vertical for my portable operations, but often, when I have space for a full-size dipole, I wished that I still had the TD-1. (which also was available in a military version from Rockwell-Collins called, I believe, the HD-4000) I've tried a few modern light-weight incarnations of the reel dipole, and although they work fine none of them had the sturdy reassuring feel of the old TD-1.
An aluminum U-profile, 3/4" wide and 1/2" high, normally used to protect the edge of plywood, looked like a good choice for a frame to hold the reels. With a bit of handiwork with a metal saw I fashioned the two brackets that hold the tapes. They are bolted together with a 4 1/2" bolt with nylon spacers in between. (all the materials I used are readily available in hardware stores).
The old TD-1 had a screw-down clamp to stop the tape, which also served as the electrical connection to the tape, and the dust and dirt that gathered in that spot rubbed off the markings on the tapes pretty quickly. So it's probably not a disadvantage that these reels have nothing of the sort. I chose to make the actual electrical connection using binder clips that squeeze a short length of grounding strap firmly onto the tape. Since the tape is coated you have to use steel wool to remove the coating over some length around the desired point of contact, and it turns out that this works quite well.
The finished product is definitely not designed for the backpacker, but it conveys the heft and sturdiness that I remember from the TD-1. With its aluminum frame it is probably even more solid than the original. Taking a clue from the original I have attached a laminated frequency-to-length conversion chart to the back. Unlike the TD-1 with its 66' reels the two 50' reels will not permit operation on 80m. However, since I'm rarely ever on 80m and my K1 is not configured for it, that's not something I miss. I believe that similar tapes are available in 100' length, so you could construct this antenna to cover 80m, too. The whole thing looks and feels professional and solid, which was my most important objective.
My construction has a SO-239 connector that directly connects to the antenna without a balun. I felt that an electrically balanced situation is probably not going to occur in the odd locations that this antenna will be used in, and therefore the added complexity of a balun didn't seem justified - the TD-1 didn't have one either. (Although a small balun can easily be added to the construction.)
How does it perform? That's, of course, hard to say since I can't switch to another antenna easily. Stainless steels tapes are not a particularly good material for antennas if you're looking for low resistance material - but then, real wire antennas out there gather a coat of oxidation pretty quickly which introduces some resistive loss, too. Over all the antenna seems to perform quite well - I get into Europe and South America on 20m with 5W quite regularly from the East Coast despite the lackluster conditions. Setup is very simple using the length chart, and my Elecraft K1 has no problems giving me a 1:1 SWR every time. For a total cost of about $25 and a few bruises on my fingers from the metal work I have an antenna that is at least as rugged as the TD-1 and should travel with me for a long time to come. (and this time I'm not going to sell it unless you make me an offer that I can't refuse ...)
| KI4WCA | 2007-07-15 | |
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| RE: Reinventing the Tape Dipole | ||
| half rhombic.KI4WCA Reply to a comment by : WA8MEA on 2007-07-02 Yup. And it starts with a solid understanding of theory - but doesn't end there. 73 de Jim, N2EY ***************************************** Agree 100%, Jim. If it wasn't for theory, we wouldn't know at what length to start cutting the wires for our dipoles. Speaking of dipoles, I still don't have a winner on that trivia question above. Nice little 40 meter QRP transmitter plus 7.040 Meg crystal is waiting to be won! FREE! No strings! (I do a surprise contest every once in a while here in these forums....) The trivia question is: What is another name for the "Inverted Vee" antenna???? Send your answer to: tinytenna@hotmail.com 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : N2EY on 2007-07-02 "Amen to that Jim, and thanks for the compliment." You're welcome! "I don't get worked up over theory, because it is what it is: theory. And in my 40 plus years in hamming, I have always found anomalies where something doesn't act the way the ARRL Handbook (And now computerized antenna analyzing programs....) have said it should act." Theory is important to any understanding of antennas. But it's also important to know how to apply the theory to what appears to be going on. IOW, what is of practical importance and what isn't. "Practicality IS the word." Yup. And it starts with a solid understanding of theory - but doesn't end there. 73 de Jim, N2EY Reply to a comment by : WA8MEA on 2007-07-02 Some folks get all worked up over the theory, and lose sight of the practical results. You're clearly not one of them. 73 de Jim, N2EY ************************************************* Amen to that Jim, and thanks for the compliment. I don't get worked up over theory, because it is what it is: theory. And in my 40 plus years in hamming, I have always found anomalies where something doesn't act the way the ARRL Handbook (And now computerized antenna analyzing programs....) have said it should act. Practicality IS the word. *********************************** Answer to trivia question: Alligator clip: http://www.rcbros.com/uploads/images/RcBro/4sale_031.jpg Crocodile clip: http://www.thefencingpost.com/Pictures/Foil/Body%20Cords/FF76.jpg ************************************* I was right, Jim! Larger mouth and teeth on the croc clips! I wish I could have drawn you a picture of what I was thinking. But believe me, THAT was what I was thinking. (A better analogy would have been the large and small mouth bass! Hi.) **************************************** Now here's a trivia question with a prize. How about a FREE Peanut Whistle Two 40 meter QRP transmitter complete with crystal....to the whiner....I mean WINNER. What is another name for an Inverted Vee antenna???? (You might have to dig deep into your reference books....or memories for this answer!) Send your answer to: tinytenna@hotmail.com First CORRECT answer gets it. And I will supply a reference so you know I'm not pulling it out of thin air. Hi. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-07-01 WA8MEA wrote: AF6AY: "What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack." --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. ........................................ I've not "contradicted" anything. A dipole is considered "balanced" meaning that it has two elements excited such that RF currents are of equal amplitude but of opposite phase. If one connects a conductor to one element of a dipole then the equal-but-opposite condition is upset. One CAN match the impedance at one frequency using an antenna tuner and satisfy the maximum power delivery to the antenna. However, the RF wave launching effect will not be symmetric nor will the radiation pattern be predictable without very extensive modeling. Measured radiation patterns have followed the theoretical as close as possible for conditions of IDEAL grounds (i.e., perfect conductivity). Those patterns assume NO nearby ('near-field' within 5 wavelengths) conductors; parasitic effects from such conductors would change the pattern. Elevation radiation patterns change as the dipole height is changed above the ideal ground. In any practical location (ground not next to a salt sea), the ground conductivity will vary considerably. So will the elevation radiation pattern. Add in nearby conductive wires/surfaces and there will be distortion in both elevation and azimuth patterns. What is desireable is to MINIMIZE all the distortion effects in order to get the radiation pattern optimum in the direction desired. There is NO "ideal" height of a dipole above ground. Since the elevation pattern maximum lobe keeps changing with height above ground, one picks a height that is both practical and at an angle desired. ............................................... WA8MEA: "IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun." One wavelength at 3.5 MHz is about 265 feet. I'd suggest a BALLOON, not a Balun. You haven't justified either NOT using a Balun at heights below one wavelength nor using one at heights above one wavelength. Why do you make such a claim? A dipole is INTENDED to be a balanced system. At any height above ground. Connect a conductor of length to one element and the balance is upset, pattern distorted. Contrary to anti-theory folks, the pattern CAN be calculated and modeled...but some analysis models get so complicated that it is easier to build and test a couple prototypes rather than spend days entering in computer data for a model. Use of a Balun AT the feedpoint of a dipole preserves as much balance as possible, regardless of the type of feedline connected after the Balun. There will be no assymmetry of elements due to feedlines. Further, using a 1:1 ratio Balun, a dipole's characteristic impedance is closer to common coaxial cable impedance than any open-wire or lader-line balanced feedline. .................................. WA8MEA: "Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.)" Shall we then toss all the theory books out the window? How about just hanging a wire out that window, matching to it, then going on and winning DXCC and working all the "rare ones?" Here's a hint: "Mother Nature" never once built-tested-devised an antenna (or aerial) to radiate RF from induced RF voltage-current in conductors. Humans did that. At first the designs were guesses at what might happen and a LOT of "empirical data derivation" (cut-and-try) was done. Then folk got to thinking harder, remembering J. C. Maxwell and his equations, and worked out basic theory. Then they tested the theories by building actual antennas based on those theories. Eventually it all came down to an ability to predict antenna behavior in most aspects. The "seat-of-the-pants," "gut-instinct," "screwdriver mechanic" sort of ham wants to minimize thinking about theory and get out there and DO things. Mostly they fail in their "kick-in-place-hammer-shut-and-weld" methods but won't talk about it much afterwards. Usually their talk goes a bit like: "I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system." Right...and "good quality coax cable" refuses to allow RF currents to flow on the outside of the outer conductor but is near-perfect conductivity on the inside of the outer conductor. Whatever. :-) .................................. WA8MEA: "However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here." So, your 160m dipole is 530 feet or more above ground?!? :-) .................................. WA8MEA: "As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III." I can't logically argue against Religious Tracts. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-07-01 What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun. Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.) I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system. However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here. As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-06-30 WA8MEA wrote: "Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun." ............................................... You are using balanced antennas. Are you feeding all of them with balanced feedlines? Feeding a balanced system with an unbalanced line such as coaxial cable can appear to work just fine, VSWR-wise. The RF energy will definitely transfer into the antenna. What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. A simple Balun transforms a balanced system to an unblanaced one. There is no distortion of the balanced current flow in 'balanced' antenna (due to the no-Balun direct coax connection outer conductor) and the balanced antenna pattern will be close to theoretical. Coaxial cable on the Balun's primary side (away from the antenna) can have its outer conductor grounded to earth or even isolated above ground or even go through another Balun (or Unbal, whatever) without tying it to an earth ground. The RF flow will be proper and "hot spots" in the ham shack along coax will be few and small. A 1:1 impedance ratio Balun can be made/connected so that both sides of a balanced antenna are at DC potential to unbalanced coax outer conductor. This can be a distinct safety precaution to bleed off accumulated static charge during electrical storms. A coaxial arrester can be mounted on the ground immediately below the downlead. That is considered safer for all concerned than having a DC connection far down the line inside the ham shack. A single broadband RF transformer can be constructed of heavy-guage electrical wire and a toroidal core available many frp, places (such as Dieter Gentzow's Kits-n-Parts) over the Internet. Amidon Associates has been selling Balun kits for decades in stores. They aren't "expensive" unless one makes antennas out of stripped junked transformer wire with old buttons as insulators. ....................................... WA8MEA: "Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!)" Electrons, fields and waves pay no mind to human emotions or to humans' reverence for friends. I have nothing against your friend but if you wish to repudiate a lot of tried-and-proven things about EM launching, techniques, etc., substituting reverence for your friend, that's your business. ....................................... WA8MEA: "I also understand that if you are using open wire feeder, you'd best go with a balun." WHY? Can"t your antenna tuner provide a balanced feedline connection? If it does, then check its insides for a DC path to earth ground...to bleed off static electricity build-up (not the best place to do it but better than none). Can your antenna tuner or transmitter output network handle unbalanced line outputs? If it can't, then an Unbal should be used...if for no other reason than to keep from making one side of a balanaced line as part of one antenna element (and therefore UNbalancing it). The lowest-characteristic-impedance balanced line is 300 Ohm "Twinlead." That impedance is well above the classic dipole and Vee feedpoint impedance values. It's farther out with 450 Ohm "Ladder Line." One starts out with a mismatch using high-Z balanced freedlines and it doesn't seem reasonable to make it worse. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| AA0FY | 2007-07-12 | |
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| RE: Reinventing the Tape Dipole | ||
| But You can use both "Crocodile" and "Alligator" clips as "Roach" clips! Reply to a comment by : N2DE on 2007-07-09 AB2NM: "On behalf of all hams, I appologize for how this thread degenerated ... again." I have a simple strategy to deal with the nitwits who post on this site: don't even ignore them ;-) Reply to a comment by : AB2NM on 2007-07-02 Neat idea, Ulrich. Nice article and great job on the fabrication. On behalf of all hams, I appologize for how this thread degenerated ... again. Now, perhaps we can all argue about the number of angels that can dance on the head of a pin. Who's first? | ||
| N2DE | 2007-07-09 | |
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| RE: Reinventing the Tape Dipole | ||
| AB2NM: "On behalf of all hams, I appologize for how this thread degenerated ... again." I have a simple strategy to deal with the nitwits who post on this site: don't even ignore them ;-) Reply to a comment by : AB2NM on 2007-07-02 Neat idea, Ulrich. Nice article and great job on the fabrication. On behalf of all hams, I appologize for how this thread degenerated ... again. Now, perhaps we can all argue about the number of angels that can dance on the head of a pin. Who's first? | ||
| N2EY | 2007-07-03 | |
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| RE: Reinventing the Tape Dipole | ||
| "Yup. And it starts with a solid understanding of theory - but doesn't end there. 73 de Jim, N2EY" ***************************************** "Agree 100%, Jim. If it wasn't for theory, we wouldn't know at what length to start cutting the wires for our dipoles." And if it wasn't for a knowledge of practice, we wouldn't know when to *stop* cutting those wires.... IOW, both are needed. Watch out for the person with lots of theory but not much practical experience. Like the person who lectures on the need for a balun, regardless of frequency or antenna type. -- As for the alligator-vs-crocodile clip question, it's not the size of the teeth but the construction. Note how the alligator clip has the hinge point right in the center, and the two jaws don't criss cross each other. The crocodile clip has the hinge near the end where the wire connects, and the jaws criss cross each other. 73 de Jim, N2EY Reply to a comment by : WA8MEA on 2007-07-02 Yup. And it starts with a solid understanding of theory - but doesn't end there. 73 de Jim, N2EY ***************************************** Agree 100%, Jim. If it wasn't for theory, we wouldn't know at what length to start cutting the wires for our dipoles. Speaking of dipoles, I still don't have a winner on that trivia question above. Nice little 40 meter QRP transmitter plus 7.040 Meg crystal is waiting to be won! FREE! No strings! (I do a surprise contest every once in a while here in these forums....) The trivia question is: What is another name for the "Inverted Vee" antenna???? Send your answer to: tinytenna@hotmail.com 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : N2EY on 2007-07-02 "Amen to that Jim, and thanks for the compliment." You're welcome! "I don't get worked up over theory, because it is what it is: theory. And in my 40 plus years in hamming, I have always found anomalies where something doesn't act the way the ARRL Handbook (And now computerized antenna analyzing programs....) have said it should act." Theory is important to any understanding of antennas. But it's also important to know how to apply the theory to what appears to be going on. IOW, what is of practical importance and what isn't. "Practicality IS the word." Yup. And it starts with a solid understanding of theory - but doesn't end there. 73 de Jim, N2EY Reply to a comment by : WA8MEA on 2007-07-02 Some folks get all worked up over the theory, and lose sight of the practical results. You're clearly not one of them. 73 de Jim, N2EY ************************************************* Amen to that Jim, and thanks for the compliment. I don't get worked up over theory, because it is what it is: theory. And in my 40 plus years in hamming, I have always found anomalies where something doesn't act the way the ARRL Handbook (And now computerized antenna analyzing programs....) have said it should act. Practicality IS the word. *********************************** Answer to trivia question: Alligator clip: http://www.rcbros.com/uploads/images/RcBro/4sale_031.jpg Crocodile clip: http://www.thefencingpost.com/Pictures/Foil/Body%20Cords/FF76.jpg ************************************* I was right, Jim! Larger mouth and teeth on the croc clips! I wish I could have drawn you a picture of what I was thinking. But believe me, THAT was what I was thinking. (A better analogy would have been the large and small mouth bass! Hi.) **************************************** Now here's a trivia question with a prize. How about a FREE Peanut Whistle Two 40 meter QRP transmitter complete with crystal....to the whiner....I mean WINNER. What is another name for an Inverted Vee antenna???? (You might have to dig deep into your reference books....or memories for this answer!) Send your answer to: tinytenna@hotmail.com First CORRECT answer gets it. And I will supply a reference so you know I'm not pulling it out of thin air. Hi. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-07-01 WA8MEA wrote: AF6AY: "What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack." --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. ........................................ I've not "contradicted" anything. A dipole is considered "balanced" meaning that it has two elements excited such that RF currents are of equal amplitude but of opposite phase. If one connects a conductor to one element of a dipole then the equal-but-opposite condition is upset. One CAN match the impedance at one frequency using an antenna tuner and satisfy the maximum power delivery to the antenna. However, the RF wave launching effect will not be symmetric nor will the radiation pattern be predictable without very extensive modeling. Measured radiation patterns have followed the theoretical as close as possible for conditions of IDEAL grounds (i.e., perfect conductivity). Those patterns assume NO nearby ('near-field' within 5 wavelengths) conductors; parasitic effects from such conductors would change the pattern. Elevation radiation patterns change as the dipole height is changed above the ideal ground. In any practical location (ground not next to a salt sea), the ground conductivity will vary considerably. So will the elevation radiation pattern. Add in nearby conductive wires/surfaces and there will be distortion in both elevation and azimuth patterns. What is desireable is to MINIMIZE all the distortion effects in order to get the radiation pattern optimum in the direction desired. There is NO "ideal" height of a dipole above ground. Since the elevation pattern maximum lobe keeps changing with height above ground, one picks a height that is both practical and at an angle desired. ............................................... WA8MEA: "IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun." One wavelength at 3.5 MHz is about 265 feet. I'd suggest a BALLOON, not a Balun. You haven't justified either NOT using a Balun at heights below one wavelength nor using one at heights above one wavelength. Why do you make such a claim? A dipole is INTENDED to be a balanced system. At any height above ground. Connect a conductor of length to one element and the balance is upset, pattern distorted. Contrary to anti-theory folks, the pattern CAN be calculated and modeled...but some analysis models get so complicated that it is easier to build and test a couple prototypes rather than spend days entering in computer data for a model. Use of a Balun AT the feedpoint of a dipole preserves as much balance as possible, regardless of the type of feedline connected after the Balun. There will be no assymmetry of elements due to feedlines. Further, using a 1:1 ratio Balun, a dipole's characteristic impedance is closer to common coaxial cable impedance than any open-wire or lader-line balanced feedline. .................................. WA8MEA: "Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.)" Shall we then toss all the theory books out the window? How about just hanging a wire out that window, matching to it, then going on and winning DXCC and working all the "rare ones?" Here's a hint: "Mother Nature" never once built-tested-devised an antenna (or aerial) to radiate RF from induced RF voltage-current in conductors. Humans did that. At first the designs were guesses at what might happen and a LOT of "empirical data derivation" (cut-and-try) was done. Then folk got to thinking harder, remembering J. C. Maxwell and his equations, and worked out basic theory. Then they tested the theories by building actual antennas based on those theories. Eventually it all came down to an ability to predict antenna behavior in most aspects. The "seat-of-the-pants," "gut-instinct," "screwdriver mechanic" sort of ham wants to minimize thinking about theory and get out there and DO things. Mostly they fail in their "kick-in-place-hammer-shut-and-weld" methods but won't talk about it much afterwards. Usually their talk goes a bit like: "I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system." Right...and "good quality coax cable" refuses to allow RF currents to flow on the outside of the outer conductor but is near-perfect conductivity on the inside of the outer conductor. Whatever. :-) .................................. WA8MEA: "However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here." So, your 160m dipole is 530 feet or more above ground?!? :-) .................................. WA8MEA: "As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III." I can't logically argue against Religious Tracts. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-07-01 What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun. Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.) I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system. However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here. As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-06-30 WA8MEA wrote: "Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun." ............................................... You are using balanced antennas. Are you feeding all of them with balanced feedlines? Feeding a balanced system with an unbalanced line such as coaxial cable can appear to work just fine, VSWR-wise. The RF energy will definitely transfer into the antenna. What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. A simple Balun transforms a balanced system to an unblanaced one. There is no distortion of the balanced current flow in 'balanced' antenna (due to the no-Balun direct coax connection outer conductor) and the balanced antenna pattern will be close to theoretical. Coaxial cable on the Balun's primary side (away from the antenna) can have its outer conductor grounded to earth or even isolated above ground or even go through another Balun (or Unbal, whatever) without tying it to an earth ground. The RF flow will be proper and "hot spots" in the ham shack along coax will be few and small. A 1:1 impedance ratio Balun can be made/connected so that both sides of a balanced antenna are at DC potential to unbalanced coax outer conductor. This can be a distinct safety precaution to bleed off accumulated static charge during electrical storms. A coaxial arrester can be mounted on the ground immediately below the downlead. That is considered safer for all concerned than having a DC connection far down the line inside the ham shack. A single broadband RF transformer can be constructed of heavy-guage electrical wire and a toroidal core available many frp, places (such as Dieter Gentzow's Kits-n-Parts) over the Internet. Amidon Associates has been selling Balun kits for decades in stores. They aren't "expensive" unless one makes antennas out of stripped junked transformer wire with old buttons as insulators. ....................................... WA8MEA: "Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!)" Electrons, fields and waves pay no mind to human emotions or to humans' reverence for friends. I have nothing against your friend but if you wish to repudiate a lot of tried-and-proven things about EM launching, techniques, etc., substituting reverence for your friend, that's your business. ....................................... WA8MEA: "I also understand that if you are using open wire feeder, you'd best go with a balun." WHY? Can"t your antenna tuner provide a balanced feedline connection? If it does, then check its insides for a DC path to earth ground...to bleed off static electricity build-up (not the best place to do it but better than none). Can your antenna tuner or transmitter output network handle unbalanced line outputs? If it can't, then an Unbal should be used...if for no other reason than to keep from making one side of a balanaced line as part of one antenna element (and therefore UNbalancing it). The lowest-characteristic-impedance balanced line is 300 Ohm "Twinlead." That impedance is well above the classic dipole and Vee feedpoint impedance values. It's farther out with 450 Ohm "Ladder Line." One starts out with a mismatch using high-Z balanced freedlines and it doesn't seem reasonable to make it worse. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| WA8MEA | 2007-07-02 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| Yup. And it starts with a solid understanding of theory - but doesn't end there. 73 de Jim, N2EY ***************************************** Agree 100%, Jim. If it wasn't for theory, we wouldn't know at what length to start cutting the wires for our dipoles. Speaking of dipoles, I still don't have a winner on that trivia question above. Nice little 40 meter QRP transmitter plus 7.040 Meg crystal is waiting to be won! FREE! No strings! (I do a surprise contest every once in a while here in these forums....) The trivia question is: What is another name for the "Inverted Vee" antenna???? Send your answer to: tinytenna@hotmail.com 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : N2EY on 2007-07-02 "Amen to that Jim, and thanks for the compliment." You're welcome! "I don't get worked up over theory, because it is what it is: theory. And in my 40 plus years in hamming, I have always found anomalies where something doesn't act the way the ARRL Handbook (And now computerized antenna analyzing programs....) have said it should act." Theory is important to any understanding of antennas. But it's also important to know how to apply the theory to what appears to be going on. IOW, what is of practical importance and what isn't. "Practicality IS the word." Yup. And it starts with a solid understanding of theory - but doesn't end there. 73 de Jim, N2EY Reply to a comment by : WA8MEA on 2007-07-02 Some folks get all worked up over the theory, and lose sight of the practical results. You're clearly not one of them. 73 de Jim, N2EY ************************************************* Amen to that Jim, and thanks for the compliment. I don't get worked up over theory, because it is what it is: theory. And in my 40 plus years in hamming, I have always found anomalies where something doesn't act the way the ARRL Handbook (And now computerized antenna analyzing programs....) have said it should act. Practicality IS the word. *********************************** Answer to trivia question: Alligator clip: http://www.rcbros.com/uploads/images/RcBro/4sale_031.jpg Crocodile clip: http://www.thefencingpost.com/Pictures/Foil/Body%20Cords/FF76.jpg ************************************* I was right, Jim! Larger mouth and teeth on the croc clips! I wish I could have drawn you a picture of what I was thinking. But believe me, THAT was what I was thinking. (A better analogy would have been the large and small mouth bass! Hi.) **************************************** Now here's a trivia question with a prize. How about a FREE Peanut Whistle Two 40 meter QRP transmitter complete with crystal....to the whiner....I mean WINNER. What is another name for an Inverted Vee antenna???? (You might have to dig deep into your reference books....or memories for this answer!) Send your answer to: tinytenna@hotmail.com First CORRECT answer gets it. And I will supply a reference so you know I'm not pulling it out of thin air. Hi. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-07-01 WA8MEA wrote: AF6AY: "What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack." --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. ........................................ I've not "contradicted" anything. A dipole is considered "balanced" meaning that it has two elements excited such that RF currents are of equal amplitude but of opposite phase. If one connects a conductor to one element of a dipole then the equal-but-opposite condition is upset. One CAN match the impedance at one frequency using an antenna tuner and satisfy the maximum power delivery to the antenna. However, the RF wave launching effect will not be symmetric nor will the radiation pattern be predictable without very extensive modeling. Measured radiation patterns have followed the theoretical as close as possible for conditions of IDEAL grounds (i.e., perfect conductivity). Those patterns assume NO nearby ('near-field' within 5 wavelengths) conductors; parasitic effects from such conductors would change the pattern. Elevation radiation patterns change as the dipole height is changed above the ideal ground. In any practical location (ground not next to a salt sea), the ground conductivity will vary considerably. So will the elevation radiation pattern. Add in nearby conductive wires/surfaces and there will be distortion in both elevation and azimuth patterns. What is desireable is to MINIMIZE all the distortion effects in order to get the radiation pattern optimum in the direction desired. There is NO "ideal" height of a dipole above ground. Since the elevation pattern maximum lobe keeps changing with height above ground, one picks a height that is both practical and at an angle desired. ............................................... WA8MEA: "IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun." One wavelength at 3.5 MHz is about 265 feet. I'd suggest a BALLOON, not a Balun. You haven't justified either NOT using a Balun at heights below one wavelength nor using one at heights above one wavelength. Why do you make such a claim? A dipole is INTENDED to be a balanced system. At any height above ground. Connect a conductor of length to one element and the balance is upset, pattern distorted. Contrary to anti-theory folks, the pattern CAN be calculated and modeled...but some analysis models get so complicated that it is easier to build and test a couple prototypes rather than spend days entering in computer data for a model. Use of a Balun AT the feedpoint of a dipole preserves as much balance as possible, regardless of the type of feedline connected after the Balun. There will be no assymmetry of elements due to feedlines. Further, using a 1:1 ratio Balun, a dipole's characteristic impedance is closer to common coaxial cable impedance than any open-wire or lader-line balanced feedline. .................................. WA8MEA: "Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.)" Shall we then toss all the theory books out the window? How about just hanging a wire out that window, matching to it, then going on and winning DXCC and working all the "rare ones?" Here's a hint: "Mother Nature" never once built-tested-devised an antenna (or aerial) to radiate RF from induced RF voltage-current in conductors. Humans did that. At first the designs were guesses at what might happen and a LOT of "empirical data derivation" (cut-and-try) was done. Then folk got to thinking harder, remembering J. C. Maxwell and his equations, and worked out basic theory. Then they tested the theories by building actual antennas based on those theories. Eventually it all came down to an ability to predict antenna behavior in most aspects. The "seat-of-the-pants," "gut-instinct," "screwdriver mechanic" sort of ham wants to minimize thinking about theory and get out there and DO things. Mostly they fail in their "kick-in-place-hammer-shut-and-weld" methods but won't talk about it much afterwards. Usually their talk goes a bit like: "I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system." Right...and "good quality coax cable" refuses to allow RF currents to flow on the outside of the outer conductor but is near-perfect conductivity on the inside of the outer conductor. Whatever. :-) .................................. WA8MEA: "However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here." So, your 160m dipole is 530 feet or more above ground?!? :-) .................................. WA8MEA: "As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III." I can't logically argue against Religious Tracts. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-07-01 What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun. Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.) I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system. However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here. As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-06-30 WA8MEA wrote: "Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun." ............................................... You are using balanced antennas. Are you feeding all of them with balanced feedlines? Feeding a balanced system with an unbalanced line such as coaxial cable can appear to work just fine, VSWR-wise. The RF energy will definitely transfer into the antenna. What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. A simple Balun transforms a balanced system to an unblanaced one. There is no distortion of the balanced current flow in 'balanced' antenna (due to the no-Balun direct coax connection outer conductor) and the balanced antenna pattern will be close to theoretical. Coaxial cable on the Balun's primary side (away from the antenna) can have its outer conductor grounded to earth or even isolated above ground or even go through another Balun (or Unbal, whatever) without tying it to an earth ground. The RF flow will be proper and "hot spots" in the ham shack along coax will be few and small. A 1:1 impedance ratio Balun can be made/connected so that both sides of a balanced antenna are at DC potential to unbalanced coax outer conductor. This can be a distinct safety precaution to bleed off accumulated static charge during electrical storms. A coaxial arrester can be mounted on the ground immediately below the downlead. That is considered safer for all concerned than having a DC connection far down the line inside the ham shack. A single broadband RF transformer can be constructed of heavy-guage electrical wire and a toroidal core available many frp, places (such as Dieter Gentzow's Kits-n-Parts) over the Internet. Amidon Associates has been selling Balun kits for decades in stores. They aren't "expensive" unless one makes antennas out of stripped junked transformer wire with old buttons as insulators. ....................................... WA8MEA: "Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!)" Electrons, fields and waves pay no mind to human emotions or to humans' reverence for friends. I have nothing against your friend but if you wish to repudiate a lot of tried-and-proven things about EM launching, techniques, etc., substituting reverence for your friend, that's your business. ....................................... WA8MEA: "I also understand that if you are using open wire feeder, you'd best go with a balun." WHY? Can"t your antenna tuner provide a balanced feedline connection? If it does, then check its insides for a DC path to earth ground...to bleed off static electricity build-up (not the best place to do it but better than none). Can your antenna tuner or transmitter output network handle unbalanced line outputs? If it can't, then an Unbal should be used...if for no other reason than to keep from making one side of a balanaced line as part of one antenna element (and therefore UNbalancing it). The lowest-characteristic-impedance balanced line is 300 Ohm "Twinlead." That impedance is well above the classic dipole and Vee feedpoint impedance values. It's farther out with 450 Ohm "Ladder Line." One starts out with a mismatch using high-Z balanced freedlines and it doesn't seem reasonable to make it worse. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| RADIOGUYR2 | 2007-07-02 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| Yep good idea but, to heavy. Doesn't work correctly tape won't stay at the setting make sure you twist the tape in lenght so as not to have a narrow signal in one direction. With the tape being 1/2 inch wide by 0.030 thick don't go relying on it being the same after you strech it out and/or try for a wire signal pattern. other than just a few problems, like having a crane lift it up in the center (ya and what is the tension on the tape when you span it out on 75 meters?--- not to mention the weight of the coax hanging down--- to try and keep it in a flat plane ) , its a great idea whose time came and went. Reply to a comment by : AB2NM on 2007-07-02 Neat idea, Ulrich. Nice article and great job on the fabrication. On behalf of all hams, I appologize for how this thread degenerated ... again. Now, perhaps we can all argue about the number of angels that can dance on the head of a pin. Who's first? | ||
| AB2NM | 2007-07-02 | |
|---|---|---|
| Reinventing the Tape Dipole | ||
| Neat idea, Ulrich. Nice article and great job on the fabrication. On behalf of all hams, I appologize for how this thread degenerated ... again. Now, perhaps we can all argue about the number of angels that can dance on the head of a pin. Who's first? | ||
| N2EY | 2007-07-02 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| "Amen to that Jim, and thanks for the compliment." You're welcome! "I don't get worked up over theory, because it is what it is: theory. And in my 40 plus years in hamming, I have always found anomalies where something doesn't act the way the ARRL Handbook (And now computerized antenna analyzing programs....) have said it should act." Theory is important to any understanding of antennas. But it's also important to know how to apply the theory to what appears to be going on. IOW, what is of practical importance and what isn't. "Practicality IS the word." Yup. And it starts with a solid understanding of theory - but doesn't end there. 73 de Jim, N2EY Reply to a comment by : WA8MEA on 2007-07-02 Some folks get all worked up over the theory, and lose sight of the practical results. You're clearly not one of them. 73 de Jim, N2EY ************************************************* Amen to that Jim, and thanks for the compliment. I don't get worked up over theory, because it is what it is: theory. And in my 40 plus years in hamming, I have always found anomalies where something doesn't act the way the ARRL Handbook (And now computerized antenna analyzing programs....) have said it should act. Practicality IS the word. *********************************** Answer to trivia question: Alligator clip: http://www.rcbros.com/uploads/images/RcBro/4sale_031.jpg Crocodile clip: http://www.thefencingpost.com/Pictures/Foil/Body%20Cords/FF76.jpg ************************************* I was right, Jim! Larger mouth and teeth on the croc clips! I wish I could have drawn you a picture of what I was thinking. But believe me, THAT was what I was thinking. (A better analogy would have been the large and small mouth bass! Hi.) **************************************** Now here's a trivia question with a prize. How about a FREE Peanut Whistle Two 40 meter QRP transmitter complete with crystal....to the whiner....I mean WINNER. What is another name for an Inverted Vee antenna???? (You might have to dig deep into your reference books....or memories for this answer!) Send your answer to: tinytenna@hotmail.com First CORRECT answer gets it. And I will supply a reference so you know I'm not pulling it out of thin air. Hi. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-07-01 WA8MEA wrote: AF6AY: "What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack." --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. ........................................ I've not "contradicted" anything. A dipole is considered "balanced" meaning that it has two elements excited such that RF currents are of equal amplitude but of opposite phase. If one connects a conductor to one element of a dipole then the equal-but-opposite condition is upset. One CAN match the impedance at one frequency using an antenna tuner and satisfy the maximum power delivery to the antenna. However, the RF wave launching effect will not be symmetric nor will the radiation pattern be predictable without very extensive modeling. Measured radiation patterns have followed the theoretical as close as possible for conditions of IDEAL grounds (i.e., perfect conductivity). Those patterns assume NO nearby ('near-field' within 5 wavelengths) conductors; parasitic effects from such conductors would change the pattern. Elevation radiation patterns change as the dipole height is changed above the ideal ground. In any practical location (ground not next to a salt sea), the ground conductivity will vary considerably. So will the elevation radiation pattern. Add in nearby conductive wires/surfaces and there will be distortion in both elevation and azimuth patterns. What is desireable is to MINIMIZE all the distortion effects in order to get the radiation pattern optimum in the direction desired. There is NO "ideal" height of a dipole above ground. Since the elevation pattern maximum lobe keeps changing with height above ground, one picks a height that is both practical and at an angle desired. ............................................... WA8MEA: "IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun." One wavelength at 3.5 MHz is about 265 feet. I'd suggest a BALLOON, not a Balun. You haven't justified either NOT using a Balun at heights below one wavelength nor using one at heights above one wavelength. Why do you make such a claim? A dipole is INTENDED to be a balanced system. At any height above ground. Connect a conductor of length to one element and the balance is upset, pattern distorted. Contrary to anti-theory folks, the pattern CAN be calculated and modeled...but some analysis models get so complicated that it is easier to build and test a couple prototypes rather than spend days entering in computer data for a model. Use of a Balun AT the feedpoint of a dipole preserves as much balance as possible, regardless of the type of feedline connected after the Balun. There will be no assymmetry of elements due to feedlines. Further, using a 1:1 ratio Balun, a dipole's characteristic impedance is closer to common coaxial cable impedance than any open-wire or lader-line balanced feedline. .................................. WA8MEA: "Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.)" Shall we then toss all the theory books out the window? How about just hanging a wire out that window, matching to it, then going on and winning DXCC and working all the "rare ones?" Here's a hint: "Mother Nature" never once built-tested-devised an antenna (or aerial) to radiate RF from induced RF voltage-current in conductors. Humans did that. At first the designs were guesses at what might happen and a LOT of "empirical data derivation" (cut-and-try) was done. Then folk got to thinking harder, remembering J. C. Maxwell and his equations, and worked out basic theory. Then they tested the theories by building actual antennas based on those theories. Eventually it all came down to an ability to predict antenna behavior in most aspects. The "seat-of-the-pants," "gut-instinct," "screwdriver mechanic" sort of ham wants to minimize thinking about theory and get out there and DO things. Mostly they fail in their "kick-in-place-hammer-shut-and-weld" methods but won't talk about it much afterwards. Usually their talk goes a bit like: "I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system." Right...and "good quality coax cable" refuses to allow RF currents to flow on the outside of the outer conductor but is near-perfect conductivity on the inside of the outer conductor. Whatever. :-) .................................. WA8MEA: "However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here." So, your 160m dipole is 530 feet or more above ground?!? :-) .................................. WA8MEA: "As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III." I can't logically argue against Religious Tracts. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-07-01 What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun. Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.) I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system. However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here. As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-06-30 WA8MEA wrote: "Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun." ............................................... You are using balanced antennas. Are you feeding all of them with balanced feedlines? Feeding a balanced system with an unbalanced line such as coaxial cable can appear to work just fine, VSWR-wise. The RF energy will definitely transfer into the antenna. What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. A simple Balun transforms a balanced system to an unblanaced one. There is no distortion of the balanced current flow in 'balanced' antenna (due to the no-Balun direct coax connection outer conductor) and the balanced antenna pattern will be close to theoretical. Coaxial cable on the Balun's primary side (away from the antenna) can have its outer conductor grounded to earth or even isolated above ground or even go through another Balun (or Unbal, whatever) without tying it to an earth ground. The RF flow will be proper and "hot spots" in the ham shack along coax will be few and small. A 1:1 impedance ratio Balun can be made/connected so that both sides of a balanced antenna are at DC potential to unbalanced coax outer conductor. This can be a distinct safety precaution to bleed off accumulated static charge during electrical storms. A coaxial arrester can be mounted on the ground immediately below the downlead. That is considered safer for all concerned than having a DC connection far down the line inside the ham shack. A single broadband RF transformer can be constructed of heavy-guage electrical wire and a toroidal core available many frp, places (such as Dieter Gentzow's Kits-n-Parts) over the Internet. Amidon Associates has been selling Balun kits for decades in stores. They aren't "expensive" unless one makes antennas out of stripped junked transformer wire with old buttons as insulators. ....................................... WA8MEA: "Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!)" Electrons, fields and waves pay no mind to human emotions or to humans' reverence for friends. I have nothing against your friend but if you wish to repudiate a lot of tried-and-proven things about EM launching, techniques, etc., substituting reverence for your friend, that's your business. ....................................... WA8MEA: "I also understand that if you are using open wire feeder, you'd best go with a balun." WHY? Can"t your antenna tuner provide a balanced feedline connection? If it does, then check its insides for a DC path to earth ground...to bleed off static electricity build-up (not the best place to do it but better than none). Can your antenna tuner or transmitter output network handle unbalanced line outputs? If it can't, then an Unbal should be used...if for no other reason than to keep from making one side of a balanaced line as part of one antenna element (and therefore UNbalancing it). The lowest-characteristic-impedance balanced line is 300 Ohm "Twinlead." That impedance is well above the classic dipole and Vee feedpoint impedance values. It's farther out with 450 Ohm "Ladder Line." One starts out with a mismatch using high-Z balanced freedlines and it doesn't seem reasonable to make it worse. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| WA8MEA | 2007-07-02 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| Some folks get all worked up over the theory, and lose sight of the practical results. You're clearly not one of them. 73 de Jim, N2EY ************************************************* Amen to that Jim, and thanks for the compliment. I don't get worked up over theory, because it is what it is: theory. And in my 40 plus years in hamming, I have always found anomalies where something doesn't act the way the ARRL Handbook (And now computerized antenna analyzing programs....) have said it should act. Practicality IS the word. *********************************** Answer to trivia question: Alligator clip: http://www.rcbros.com/uploads/images/RcBro/4sale_031.jpg Crocodile clip: http://www.thefencingpost.com/Pictures/Foil/Body%20Cords/FF76.jpg ************************************* I was right, Jim! Larger mouth and teeth on the croc clips! I wish I could have drawn you a picture of what I was thinking. But believe me, THAT was what I was thinking. (A better analogy would have been the large and small mouth bass! Hi.) **************************************** Now here's a trivia question with a prize. How about a FREE Peanut Whistle Two 40 meter QRP transmitter complete with crystal....to the whiner....I mean WINNER. What is another name for an Inverted Vee antenna???? (You might have to dig deep into your reference books....or memories for this answer!) Send your answer to: tinytenna@hotmail.com First CORRECT answer gets it. And I will supply a reference so you know I'm not pulling it out of thin air. Hi. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-07-01 WA8MEA wrote: AF6AY: "What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack." --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. ........................................ I've not "contradicted" anything. A dipole is considered "balanced" meaning that it has two elements excited such that RF currents are of equal amplitude but of opposite phase. If one connects a conductor to one element of a dipole then the equal-but-opposite condition is upset. One CAN match the impedance at one frequency using an antenna tuner and satisfy the maximum power delivery to the antenna. However, the RF wave launching effect will not be symmetric nor will the radiation pattern be predictable without very extensive modeling. Measured radiation patterns have followed the theoretical as close as possible for conditions of IDEAL grounds (i.e., perfect conductivity). Those patterns assume NO nearby ('near-field' within 5 wavelengths) conductors; parasitic effects from such conductors would change the pattern. Elevation radiation patterns change as the dipole height is changed above the ideal ground. In any practical location (ground not next to a salt sea), the ground conductivity will vary considerably. So will the elevation radiation pattern. Add in nearby conductive wires/surfaces and there will be distortion in both elevation and azimuth patterns. What is desireable is to MINIMIZE all the distortion effects in order to get the radiation pattern optimum in the direction desired. There is NO "ideal" height of a dipole above ground. Since the elevation pattern maximum lobe keeps changing with height above ground, one picks a height that is both practical and at an angle desired. ............................................... WA8MEA: "IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun." One wavelength at 3.5 MHz is about 265 feet. I'd suggest a BALLOON, not a Balun. You haven't justified either NOT using a Balun at heights below one wavelength nor using one at heights above one wavelength. Why do you make such a claim? A dipole is INTENDED to be a balanced system. At any height above ground. Connect a conductor of length to one element and the balance is upset, pattern distorted. Contrary to anti-theory folks, the pattern CAN be calculated and modeled...but some analysis models get so complicated that it is easier to build and test a couple prototypes rather than spend days entering in computer data for a model. Use of a Balun AT the feedpoint of a dipole preserves as much balance as possible, regardless of the type of feedline connected after the Balun. There will be no assymmetry of elements due to feedlines. Further, using a 1:1 ratio Balun, a dipole's characteristic impedance is closer to common coaxial cable impedance than any open-wire or lader-line balanced feedline. .................................. WA8MEA: "Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.)" Shall we then toss all the theory books out the window? How about just hanging a wire out that window, matching to it, then going on and winning DXCC and working all the "rare ones?" Here's a hint: "Mother Nature" never once built-tested-devised an antenna (or aerial) to radiate RF from induced RF voltage-current in conductors. Humans did that. At first the designs were guesses at what might happen and a LOT of "empirical data derivation" (cut-and-try) was done. Then folk got to thinking harder, remembering J. C. Maxwell and his equations, and worked out basic theory. Then they tested the theories by building actual antennas based on those theories. Eventually it all came down to an ability to predict antenna behavior in most aspects. The "seat-of-the-pants," "gut-instinct," "screwdriver mechanic" sort of ham wants to minimize thinking about theory and get out there and DO things. Mostly they fail in their "kick-in-place-hammer-shut-and-weld" methods but won't talk about it much afterwards. Usually their talk goes a bit like: "I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system." Right...and "good quality coax cable" refuses to allow RF currents to flow on the outside of the outer conductor but is near-perfect conductivity on the inside of the outer conductor. Whatever. :-) .................................. WA8MEA: "However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here." So, your 160m dipole is 530 feet or more above ground?!? :-) .................................. WA8MEA: "As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III." I can't logically argue against Religious Tracts. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-07-01 What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun. Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.) I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system. However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here. As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-06-30 WA8MEA wrote: "Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun." ............................................... You are using balanced antennas. Are you feeding all of them with balanced feedlines? Feeding a balanced system with an unbalanced line such as coaxial cable can appear to work just fine, VSWR-wise. The RF energy will definitely transfer into the antenna. What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. A simple Balun transforms a balanced system to an unblanaced one. There is no distortion of the balanced current flow in 'balanced' antenna (due to the no-Balun direct coax connection outer conductor) and the balanced antenna pattern will be close to theoretical. Coaxial cable on the Balun's primary side (away from the antenna) can have its outer conductor grounded to earth or even isolated above ground or even go through another Balun (or Unbal, whatever) without tying it to an earth ground. The RF flow will be proper and "hot spots" in the ham shack along coax will be few and small. A 1:1 impedance ratio Balun can be made/connected so that both sides of a balanced antenna are at DC potential to unbalanced coax outer conductor. This can be a distinct safety precaution to bleed off accumulated static charge during electrical storms. A coaxial arrester can be mounted on the ground immediately below the downlead. That is considered safer for all concerned than having a DC connection far down the line inside the ham shack. A single broadband RF transformer can be constructed of heavy-guage electrical wire and a toroidal core available many frp, places (such as Dieter Gentzow's Kits-n-Parts) over the Internet. Amidon Associates has been selling Balun kits for decades in stores. They aren't "expensive" unless one makes antennas out of stripped junked transformer wire with old buttons as insulators. ....................................... WA8MEA: "Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!)" Electrons, fields and waves pay no mind to human emotions or to humans' reverence for friends. I have nothing against your friend but if you wish to repudiate a lot of tried-and-proven things about EM launching, techniques, etc., substituting reverence for your friend, that's your business. ....................................... WA8MEA: "I also understand that if you are using open wire feeder, you'd best go with a balun." WHY? Can"t your antenna tuner provide a balanced feedline connection? If it does, then check its insides for a DC path to earth ground...to bleed off static electricity build-up (not the best place to do it but better than none). Can your antenna tuner or transmitter output network handle unbalanced line outputs? If it can't, then an Unbal should be used...if for no other reason than to keep from making one side of a balanaced line as part of one antenna element (and therefore UNbalancing it). The lowest-characteristic-impedance balanced line is 300 Ohm "Twinlead." That impedance is well above the classic dipole and Vee feedpoint impedance values. It's farther out with 450 Ohm "Ladder Line." One starts out with a mismatch using high-Z balanced freedlines and it doesn't seem reasonable to make it worse. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| N2EY | 2007-07-02 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| WA8MEA wrote: "IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun. Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.) I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system." I think there's an important point being missed here: How much does it matter? Feed a balanced antenna with an unbalanced feedline, and things won't be perfectly balanced. There will be "RF current on the outside of the coax", aka "common mode currents" aka "the feedline radiates" aka "unbalance". Not a maybe - it will happen. But how much? 50% of the total power? 10% 5%? 1%? And how much practical difference will it make? Will there be dangerous levels of RF in the shack and on the feedline? RFI? Poor antenna performance? Most of all, will adding a balun at the feedpoint make a real, measurable and *practical* difference in antenna performance? Or will it just be an expensive center insulator? In theory, you should always use a balun. In practice, it's not that simple. It's even possible to be better off without a balun than with one, because practical baluns aren't perfect. Where a balun can be really necessary is in applications where even slight radiation from the coax can make a big difference. Say you put up a beam and don't use a balun, and the resulting unbalance results in the coax radiating 5% of the applied power. If all you want is forward gain, that 5% won't make any difference at all. But if you want a lot of front-to-back and/or front-to-side rejection, you may find that you can't get any nulls deeper than -13 dBi, because the coax radiation takes over. Whether that matters depends on the application. Some folks get all worked up over the theory, and lose sight of the practical results. You're clearly not one of them. 73 de Jim, N2EY --- Answer to trivia question: Alligator clip: http://www.rcbros.com/uploads/images/RcBro/4sale_031.jpg Crocodile clip: http://www.thefencingpost.com/Pictures/Foil/Body%20Cords/FF76.jpg Reply to a comment by : WA8MEA on 2007-07-01 What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun. Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.) I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system. However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here. As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-06-30 WA8MEA wrote: "Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun." ............................................... You are using balanced antennas. Are you feeding all of them with balanced feedlines? Feeding a balanced system with an unbalanced line such as coaxial cable can appear to work just fine, VSWR-wise. The RF energy will definitely transfer into the antenna. What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. A simple Balun transforms a balanced system to an unblanaced one. There is no distortion of the balanced current flow in 'balanced' antenna (due to the no-Balun direct coax connection outer conductor) and the balanced antenna pattern will be close to theoretical. Coaxial cable on the Balun's primary side (away from the antenna) can have its outer conductor grounded to earth or even isolated above ground or even go through another Balun (or Unbal, whatever) without tying it to an earth ground. The RF flow will be proper and "hot spots" in the ham shack along coax will be few and small. A 1:1 impedance ratio Balun can be made/connected so that both sides of a balanced antenna are at DC potential to unbalanced coax outer conductor. This can be a distinct safety precaution to bleed off accumulated static charge during electrical storms. A coaxial arrester can be mounted on the ground immediately below the downlead. That is considered safer for all concerned than having a DC connection far down the line inside the ham shack. A single broadband RF transformer can be constructed of heavy-guage electrical wire and a toroidal core available many frp, places (such as Dieter Gentzow's Kits-n-Parts) over the Internet. Amidon Associates has been selling Balun kits for decades in stores. They aren't "expensive" unless one makes antennas out of stripped junked transformer wire with old buttons as insulators. ....................................... WA8MEA: "Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!)" Electrons, fields and waves pay no mind to human emotions or to humans' reverence for friends. I have nothing against your friend but if you wish to repudiate a lot of tried-and-proven things about EM launching, techniques, etc., substituting reverence for your friend, that's your business. ....................................... WA8MEA: "I also understand that if you are using open wire feeder, you'd best go with a balun." WHY? Can"t your antenna tuner provide a balanced feedline connection? If it does, then check its insides for a DC path to earth ground...to bleed off static electricity build-up (not the best place to do it but better than none). Can your antenna tuner or transmitter output network handle unbalanced line outputs? If it can't, then an Unbal should be used...if for no other reason than to keep from making one side of a balanaced line as part of one antenna element (and therefore UNbalancing it). The lowest-characteristic-impedance balanced line is 300 Ohm "Twinlead." That impedance is well above the classic dipole and Vee feedpoint impedance values. It's farther out with 450 Ohm "Ladder Line." One starts out with a mismatch using high-Z balanced freedlines and it doesn't seem reasonable to make it worse. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| WA8MEA | 2007-07-01 | |
|---|---|---|
| RE: Something Completely Different - Clip Trivia! | ||
| I can't logically argue against Religious Tracts. 73, Len AF6AY ************************************* Glad to see you've put those two on the same level as God. Sterba and Lil' Paddle have been blessed with His holy wisdom.... ;-) Bill - WA8MEA Reply to a comment by : N2EY on 2007-07-01 "OoooOOO! OOOOOO! (Hand raised....swinging in the air......) I do believe the croc clips have a larger "mouth" and "teeth". Now would this bee true for our friends for the animal kingdom also? (Crocs have bigger jaws/teeth than alligators?)" Whether it's true of our animal friends or not, size isn't the difference for alligator vs. crocodile clips. Sorry 73 de Jim, N2EY Reply to a comment by : WA8MEA on 2007-06-30 OoooOOO! OOOOOO! (Hand raised....swinging in the air......) I do believe the croc clips have a larger "mouth" and "teeth". Now would this bee true for our friends for the animal kingdom also? (Crocs have bigger jaws/teeth than alligators?) Bill - WA8MEA Reply to a comment by : N2EY on 2007-06-30 "a couple of crocodile clips" OK, here's one for the trivia buffs: What's the difference between a crocodile clip and an alligator clip? (yes, there is a difference, at least according to the manufacturers) 73 de Jim, N2EY Reply to a comment by : G6HVY on 2007-06-30 Well, I'm sure I wouldn't make any claims for the efficacy of the result, but I bought two plastic-cased steel tape measures for three pounds at an open-air market locally, soldered wire loops to the ends, put a couple of crocodile clips on the lanyards they came with, hung the things from trees in a nearby park, fed 'em with coax, more croc clips and an autotuner, and had a lot of fun with my FT-817 until the gelcell faded. Cheap, enjoyable, very portable. Worked better than a slinky antenna I made and tried in a similar configuration (which detuned quite badly from moment to moment as the wind caught it; the tuner couldn't keep up), and ideal for the station-in-a-backpack I've got. (Next thing I want to try is to add SSTV to the set-up, I've got an old laptop that's more than up to the task, and the idea of live webcam-based TV from somewhere leafy sounds even more fun, but I think that'll probably need some sort of HF amplifier to fly properly. Poor old gelcell...) Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| N2EY | 2007-07-01 | |
|---|---|---|
| RE: Something Completely Different - Clip Trivia! | ||
| "OoooOOO! OOOOOO! (Hand raised....swinging in the air......) I do believe the croc clips have a larger "mouth" and "teeth". Now would this bee true for our friends for the animal kingdom also? (Crocs have bigger jaws/teeth than alligators?)" Whether it's true of our animal friends or not, size isn't the difference for alligator vs. crocodile clips. Sorry 73 de Jim, N2EY Reply to a comment by : WA8MEA on 2007-06-30 OoooOOO! OOOOOO! (Hand raised....swinging in the air......) I do believe the croc clips have a larger "mouth" and "teeth". Now would this bee true for our friends for the animal kingdom also? (Crocs have bigger jaws/teeth than alligators?) Bill - WA8MEA Reply to a comment by : N2EY on 2007-06-30 "a couple of crocodile clips" OK, here's one for the trivia buffs: What's the difference between a crocodile clip and an alligator clip? (yes, there is a difference, at least according to the manufacturers) 73 de Jim, N2EY Reply to a comment by : G6HVY on 2007-06-30 Well, I'm sure I wouldn't make any claims for the efficacy of the result, but I bought two plastic-cased steel tape measures for three pounds at an open-air market locally, soldered wire loops to the ends, put a couple of crocodile clips on the lanyards they came with, hung the things from trees in a nearby park, fed 'em with coax, more croc clips and an autotuner, and had a lot of fun with my FT-817 until the gelcell faded. Cheap, enjoyable, very portable. Worked better than a slinky antenna I made and tried in a similar configuration (which detuned quite badly from moment to moment as the wind caught it; the tuner couldn't keep up), and ideal for the station-in-a-backpack I've got. (Next thing I want to try is to add SSTV to the set-up, I've got an old laptop that's more than up to the task, and the idea of live webcam-based TV from somewhere leafy sounds even more fun, but I think that'll probably need some sort of HF amplifier to fly properly. Poor old gelcell...) Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| K6LHA | 2007-07-01 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| WA8MEA wrote: AF6AY: "What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack." --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. ........................................ I've not "contradicted" anything. A dipole is considered "balanced" meaning that it has two elements excited such that RF currents are of equal amplitude but of opposite phase. If one connects a conductor to one element of a dipole then the equal-but-opposite condition is upset. One CAN match the impedance at one frequency using an antenna tuner and satisfy the maximum power delivery to the antenna. However, the RF wave launching effect will not be symmetric nor will the radiation pattern be predictable without very extensive modeling. Measured radiation patterns have followed the theoretical as close as possible for conditions of IDEAL grounds (i.e., perfect conductivity). Those patterns assume NO nearby ('near-field' within 5 wavelengths) conductors; parasitic effects from such conductors would change the pattern. Elevation radiation patterns change as the dipole height is changed above the ideal ground. In any practical location (ground not next to a salt sea), the ground conductivity will vary considerably. So will the elevation radiation pattern. Add in nearby conductive wires/surfaces and there will be distortion in both elevation and azimuth patterns. What is desireable is to MINIMIZE all the distortion effects in order to get the radiation pattern optimum in the direction desired. There is NO "ideal" height of a dipole above ground. Since the elevation pattern maximum lobe keeps changing with height above ground, one picks a height that is both practical and at an angle desired. ............................................... WA8MEA: "IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun." One wavelength at 3.5 MHz is about 265 feet. I'd suggest a BALLOON, not a Balun. You haven't justified either NOT using a Balun at heights below one wavelength nor using one at heights above one wavelength. Why do you make such a claim? A dipole is INTENDED to be a balanced system. At any height above ground. Connect a conductor of length to one element and the balance is upset, pattern distorted. Contrary to anti-theory folks, the pattern CAN be calculated and modeled...but some analysis models get so complicated that it is easier to build and test a couple prototypes rather than spend days entering in computer data for a model. Use of a Balun AT the feedpoint of a dipole preserves as much balance as possible, regardless of the type of feedline connected after the Balun. There will be no assymmetry of elements due to feedlines. Further, using a 1:1 ratio Balun, a dipole's characteristic impedance is closer to common coaxial cable impedance than any open-wire or lader-line balanced feedline. .................................. WA8MEA: "Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.)" Shall we then toss all the theory books out the window? How about just hanging a wire out that window, matching to it, then going on and winning DXCC and working all the "rare ones?" Here's a hint: "Mother Nature" never once built-tested-devised an antenna (or aerial) to radiate RF from induced RF voltage-current in conductors. Humans did that. At first the designs were guesses at what might happen and a LOT of "empirical data derivation" (cut-and-try) was done. Then folk got to thinking harder, remembering J. C. Maxwell and his equations, and worked out basic theory. Then they tested the theories by building actual antennas based on those theories. Eventually it all came down to an ability to predict antenna behavior in most aspects. The "seat-of-the-pants," "gut-instinct," "screwdriver mechanic" sort of ham wants to minimize thinking about theory and get out there and DO things. Mostly they fail in their "kick-in-place-hammer-shut-and-weld" methods but won't talk about it much afterwards. Usually their talk goes a bit like: "I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system." Right...and "good quality coax cable" refuses to allow RF currents to flow on the outside of the outer conductor but is near-perfect conductivity on the inside of the outer conductor. Whatever. :-) .................................. WA8MEA: "However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here." So, your 160m dipole is 530 feet or more above ground?!? :-) .................................. WA8MEA: "As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III." I can't logically argue against Religious Tracts. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-07-01 What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun. Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.) I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system. However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here. As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-06-30 WA8MEA wrote: "Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun." ............................................... You are using balanced antennas. Are you feeding all of them with balanced feedlines? Feeding a balanced system with an unbalanced line such as coaxial cable can appear to work just fine, VSWR-wise. The RF energy will definitely transfer into the antenna. What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. A simple Balun transforms a balanced system to an unblanaced one. There is no distortion of the balanced current flow in 'balanced' antenna (due to the no-Balun direct coax connection outer conductor) and the balanced antenna pattern will be close to theoretical. Coaxial cable on the Balun's primary side (away from the antenna) can have its outer conductor grounded to earth or even isolated above ground or even go through another Balun (or Unbal, whatever) without tying it to an earth ground. The RF flow will be proper and "hot spots" in the ham shack along coax will be few and small. A 1:1 impedance ratio Balun can be made/connected so that both sides of a balanced antenna are at DC potential to unbalanced coax outer conductor. This can be a distinct safety precaution to bleed off accumulated static charge during electrical storms. A coaxial arrester can be mounted on the ground immediately below the downlead. That is considered safer for all concerned than having a DC connection far down the line inside the ham shack. A single broadband RF transformer can be constructed of heavy-guage electrical wire and a toroidal core available many frp, places (such as Dieter Gentzow's Kits-n-Parts) over the Internet. Amidon Associates has been selling Balun kits for decades in stores. They aren't "expensive" unless one makes antennas out of stripped junked transformer wire with old buttons as insulators. ....................................... WA8MEA: "Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!)" Electrons, fields and waves pay no mind to human emotions or to humans' reverence for friends. I have nothing against your friend but if you wish to repudiate a lot of tried-and-proven things about EM launching, techniques, etc., substituting reverence for your friend, that's your business. ....................................... WA8MEA: "I also understand that if you are using open wire feeder, you'd best go with a balun." WHY? Can"t your antenna tuner provide a balanced feedline connection? If it does, then check its insides for a DC path to earth ground...to bleed off static electricity build-up (not the best place to do it but better than none). Can your antenna tuner or transmitter output network handle unbalanced line outputs? If it can't, then an Unbal should be used...if for no other reason than to keep from making one side of a balanaced line as part of one antenna element (and therefore UNbalancing it). The lowest-characteristic-impedance balanced line is 300 Ohm "Twinlead." That impedance is well above the classic dipole and Vee feedpoint impedance values. It's farther out with 450 Ohm "Ladder Line." One starts out with a mismatch using high-Z balanced freedlines and it doesn't seem reasonable to make it worse. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| WA8MEA | 2007-07-01 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. --------------------------------------- Len: You've contradicted yourself by calling a dipole "balanced" in the first sentence, but then going on to claim it's UNbalance. (Your first sentence is actually the correct sentence IN THEORY.) Most of us DO NOT have classic donut shaped patterns because we cannot get our dipoles up above the required one wavelength to achieved that elusive donut. (Except for the higher frequencies of 20 through 10 meters.) Hence, no real need for a balun since your signal is going to be skewed anyway. IF...and it's a BIG if....and probably never an IF if you run a dipole on 75/80 meters or 160 meters....you can get your antenna up in the air a full wavelength....then I suggest a balun. Otherwise, forget about it. Your pattern is going to be what Mother Nature wants it to be. (That's why we call it antenna THEORY.) I've NEVER had ANY RF problems when using a balun-LESS dipole or Inverted Vee and good quality coax cable combined with a ground system. However, I HAVE experience RF problems trying to run a 160 meter dipole fed with coax line into a tuner that accepted coax feedline. Ladder line is the way to go here. As far as the in-shack tuner vs. using a balun at the feed point, I defer to Kurt N. Sterba & Lil Paddle and their fine books, Areials I, Aerials II and Aerials III. 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : K6LHA on 2007-06-30 WA8MEA wrote: "Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun." ............................................... You are using balanced antennas. Are you feeding all of them with balanced feedlines? Feeding a balanced system with an unbalanced line such as coaxial cable can appear to work just fine, VSWR-wise. The RF energy will definitely transfer into the antenna. What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. A simple Balun transforms a balanced system to an unblanaced one. There is no distortion of the balanced current flow in 'balanced' antenna (due to the no-Balun direct coax connection outer conductor) and the balanced antenna pattern will be close to theoretical. Coaxial cable on the Balun's primary side (away from the antenna) can have its outer conductor grounded to earth or even isolated above ground or even go through another Balun (or Unbal, whatever) without tying it to an earth ground. The RF flow will be proper and "hot spots" in the ham shack along coax will be few and small. A 1:1 impedance ratio Balun can be made/connected so that both sides of a balanced antenna are at DC potential to unbalanced coax outer conductor. This can be a distinct safety precaution to bleed off accumulated static charge during electrical storms. A coaxial arrester can be mounted on the ground immediately below the downlead. That is considered safer for all concerned than having a DC connection far down the line inside the ham shack. A single broadband RF transformer can be constructed of heavy-guage electrical wire and a toroidal core available many frp, places (such as Dieter Gentzow's Kits-n-Parts) over the Internet. Amidon Associates has been selling Balun kits for decades in stores. They aren't "expensive" unless one makes antennas out of stripped junked transformer wire with old buttons as insulators. ....................................... WA8MEA: "Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!)" Electrons, fields and waves pay no mind to human emotions or to humans' reverence for friends. I have nothing against your friend but if you wish to repudiate a lot of tried-and-proven things about EM launching, techniques, etc., substituting reverence for your friend, that's your business. ....................................... WA8MEA: "I also understand that if you are using open wire feeder, you'd best go with a balun." WHY? Can"t your antenna tuner provide a balanced feedline connection? If it does, then check its insides for a DC path to earth ground...to bleed off static electricity build-up (not the best place to do it but better than none). Can your antenna tuner or transmitter output network handle unbalanced line outputs? If it can't, then an Unbal should be used...if for no other reason than to keep from making one side of a balanaced line as part of one antenna element (and therefore UNbalancing it). The lowest-characteristic-impedance balanced line is 300 Ohm "Twinlead." That impedance is well above the classic dipole and Vee feedpoint impedance values. It's farther out with 450 Ohm "Ladder Line." One starts out with a mismatch using high-Z balanced freedlines and it doesn't seem reasonable to make it worse. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| K6LHA | 2007-06-30 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| WA8MEA wrote: "Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun." ............................................... You are using balanced antennas. Are you feeding all of them with balanced feedlines? Feeding a balanced system with an unbalanced line such as coaxial cable can appear to work just fine, VSWR-wise. The RF energy will definitely transfer into the antenna. What happens with coaxial cable directly feeding a balanced system is that the outer conductor of the coax becomes a part of one side of a balanced antenna. The end result is system UNbalance and the radiation pattern can be quite different than the classical dipole doughnut shape. What's worse is that one WILL have RF flowing along the coax outer conductor...which might or might not appear inside the ham shack. A simple Balun transforms a balanced system to an unblanaced one. There is no distortion of the balanced current flow in 'balanced' antenna (due to the no-Balun direct coax connection outer conductor) and the balanced antenna pattern will be close to theoretical. Coaxial cable on the Balun's primary side (away from the antenna) can have its outer conductor grounded to earth or even isolated above ground or even go through another Balun (or Unbal, whatever) without tying it to an earth ground. The RF flow will be proper and "hot spots" in the ham shack along coax will be few and small. A 1:1 impedance ratio Balun can be made/connected so that both sides of a balanced antenna are at DC potential to unbalanced coax outer conductor. This can be a distinct safety precaution to bleed off accumulated static charge during electrical storms. A coaxial arrester can be mounted on the ground immediately below the downlead. That is considered safer for all concerned than having a DC connection far down the line inside the ham shack. A single broadband RF transformer can be constructed of heavy-guage electrical wire and a toroidal core available many frp, places (such as Dieter Gentzow's Kits-n-Parts) over the Internet. Amidon Associates has been selling Balun kits for decades in stores. They aren't "expensive" unless one makes antennas out of stripped junked transformer wire with old buttons as insulators. ....................................... WA8MEA: "Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!)" Electrons, fields and waves pay no mind to human emotions or to humans' reverence for friends. I have nothing against your friend but if you wish to repudiate a lot of tried-and-proven things about EM launching, techniques, etc., substituting reverence for your friend, that's your business. ....................................... WA8MEA: "I also understand that if you are using open wire feeder, you'd best go with a balun." WHY? Can"t your antenna tuner provide a balanced feedline connection? If it does, then check its insides for a DC path to earth ground...to bleed off static electricity build-up (not the best place to do it but better than none). Can your antenna tuner or transmitter output network handle unbalanced line outputs? If it can't, then an Unbal should be used...if for no other reason than to keep from making one side of a balanaced line as part of one antenna element (and therefore UNbalancing it). The lowest-characteristic-impedance balanced line is 300 Ohm "Twinlead." That impedance is well above the classic dipole and Vee feedpoint impedance values. It's farther out with 450 Ohm "Ladder Line." One starts out with a mismatch using high-Z balanced freedlines and it doesn't seem reasonable to make it worse. 73, Len AF6AY Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| WA8MEA | 2007-06-30 | |
|---|---|---|
| RE: Something Completely Different - Clip Trivia! | ||
| OoooOOO! OOOOOO! (Hand raised....swinging in the air......) I do believe the croc clips have a larger "mouth" and "teeth". Now would this bee true for our friends for the animal kingdom also? (Crocs have bigger jaws/teeth than alligators?) Bill - WA8MEA Reply to a comment by : N2EY on 2007-06-30 "a couple of crocodile clips" OK, here's one for the trivia buffs: What's the difference between a crocodile clip and an alligator clip? (yes, there is a difference, at least according to the manufacturers) 73 de Jim, N2EY Reply to a comment by : G6HVY on 2007-06-30 Well, I'm sure I wouldn't make any claims for the efficacy of the result, but I bought two plastic-cased steel tape measures for three pounds at an open-air market locally, soldered wire loops to the ends, put a couple of crocodile clips on the lanyards they came with, hung the things from trees in a nearby park, fed 'em with coax, more croc clips and an autotuner, and had a lot of fun with my FT-817 until the gelcell faded. Cheap, enjoyable, very portable. Worked better than a slinky antenna I made and tried in a similar configuration (which detuned quite badly from moment to moment as the wind caught it; the tuner couldn't keep up), and ideal for the station-in-a-backpack I've got. (Next thing I want to try is to add SSTV to the set-up, I've got an old laptop that's more than up to the task, and the idea of live webcam-based TV from somewhere leafy sounds even more fun, but I think that'll probably need some sort of HF amplifier to fly properly. Poor old gelcell...) Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| N2EY | 2007-06-30 | |
|---|---|---|
| Something Completely Different - Clip Trivia! | ||
| "a couple of crocodile clips" OK, here's one for the trivia buffs: What's the difference between a crocodile clip and an alligator clip? (yes, there is a difference, at least according to the manufacturers) 73 de Jim, N2EY Reply to a comment by : G6HVY on 2007-06-30 Well, I'm sure I wouldn't make any claims for the efficacy of the result, but I bought two plastic-cased steel tape measures for three pounds at an open-air market locally, soldered wire loops to the ends, put a couple of crocodile clips on the lanyards they came with, hung the things from trees in a nearby park, fed 'em with coax, more croc clips and an autotuner, and had a lot of fun with my FT-817 until the gelcell faded. Cheap, enjoyable, very portable. Worked better than a slinky antenna I made and tried in a similar configuration (which detuned quite badly from moment to moment as the wind caught it; the tuner couldn't keep up), and ideal for the station-in-a-backpack I've got. (Next thing I want to try is to add SSTV to the set-up, I've got an old laptop that's more than up to the task, and the idea of live webcam-based TV from somewhere leafy sounds even more fun, but I think that'll probably need some sort of HF amplifier to fly properly. Poor old gelcell...) Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| G6HVY | 2007-06-30 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| Well, I'm sure I wouldn't make any claims for the efficacy of the result, but I bought two plastic-cased steel tape measures for three pounds at an open-air market locally, soldered wire loops to the ends, put a couple of crocodile clips on the lanyards they came with, hung the things from trees in a nearby park, fed 'em with coax, more croc clips and an autotuner, and had a lot of fun with my FT-817 until the gelcell faded. Cheap, enjoyable, very portable. Worked better than a slinky antenna I made and tried in a similar configuration (which detuned quite badly from moment to moment as the wind caught it; the tuner couldn't keep up), and ideal for the station-in-a-backpack I've got. (Next thing I want to try is to add SSTV to the set-up, I've got an old laptop that's more than up to the task, and the idea of live webcam-based TV from somewhere leafy sounds even more fun, but I think that'll probably need some sort of HF amplifier to fly properly. Poor old gelcell...) Reply to a comment by : WA8MEA on 2007-06-30 Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| WA8MEA | 2007-06-30 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| Uh-oh. Here comes another thread that I predict will turn nasty....but really doesn't have to. I saw someone previously use the word BALUN. Now I'm not sure of the context. But there was ONE TIME in my life that I used a balun, and that was by suggestion from a ham store salesman. After I saw my buddy using a dipole WITHOUT a balun, I asked; "Why no balun? I was told by the ham store salesman that the antenna would be absolute crap without one!" He went on to inform me that hams who still pass along the urban legend of the balun on a standard dipole fed with 50 ohm coax are actually the ones full of crap. So I believed my friend. He was smarter than me, older than me and wiser than me. So ever since that infamous day in 1970, I've used NOTHING but center insulators. The BUDWIG is a very nice center insulator and I use it on most of my dipoles and inverted vees. But I also use Van Gordon, W2AU and others. All my dipoles and inverted vees work just fine without the need expensive balun. Now I understand that some people swear at baluns, while others swear by them. So for that reason, Chris and I have decided to introduce most of our antennas with balun versions this fall. (But I still won't use one because my friend was smarter, older and wiser. And is still a ham today!) I also understand that if you are using open wire feeder, you'd best go with a balun. God bless the balun, as well as the balun-less.... 73, Bill - WA8MEA http://HamRadioFun.com Reply to a comment by : W6TH on 2007-06-30 . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| W6TH | 2007-06-30 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| . ..................Jealousy, eh?..................... .: Reply to a comment by : K8NWX on 2007-06-29 "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| K8NWX | 2007-06-29 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| "David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... " Battin' 1,000 today, Vito. May I kiss your feet, all knowing exhorbidant one? Reply to a comment by : WI7B on 2007-06-29 I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| WI7B | 2007-06-29 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
I'm supposing a tape Hertzian or Marconi monopole would work in a similar manner, with appropriate grounding? 73, ---* Ken Reply to a comment by : W6TH on 2007-06-29 . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| W6TH | 2007-06-29 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| . My final say for this post of a Reinventing the Tape Dipole. When ever you tell or inform me of something that is no good, not good, I want you in return to tell, explain, to me why it is no good and then show me how to make it good. I specialize in analytical geometry, therefor I am capable of understanding your corrected theory and not your BS. W6TH .: Reply to a comment by : K6LHA on 2007-06-29 Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| K6LHA | 2007-06-29 | |
|---|---|---|
| Reinventing the Tape Dipole | ||
| Some comments on others' comments so far: 1. Because one tape dipole was reported with -3 db gain does not mean ALL tape dipoles are lossy. 2. Height above ground per operating frequency can mean greater than 10 db difference in the elevation pattern towards a low angle above horizon line. Anyone using a method-of-moments NEC antenna analyzer program with graphics output can discover that quickly. Add to that differences in ground conductivity and reflection-parasitic effects of nearby conductors and one creates a very large variable quantity. Blanket statements of absolute loss/gain per type of antenna is invalid. 3. Weight and balance wise, it makes more sense to have two separate tape measures as reels, each at the end rather than middle. This eliminates any possibility of 'resonance' of the rolled-up tape ends. 4. Why must one use a tape measure as the basic material? A raised marker on a flexible wire of a reel would serve the same purpose and not require a look-up chart. If one can't tell the difference in unrolled length between 10m and 15m (let alone 80m and 40m) for a dipole, then its a wonder that a look-up chart can be read. :-( 5. To make an RF contact, only the coating of the convex side of the tape (usually blank) needs to be removed. Nearly all tape measures have their tapes' markings on the concave side. Coating removal of only one side permits a quick and easy check of length and connection point. Once bared, the tape metal alloy typically used in tape measures does not seem to corrode in air. 6. In the author's construction, there would be no 'resonance effects' of the rolled-up tape since the metal body of the tape measure (surrounding the tape reel) forms the "single-turn short" on an inductor to effectively cancel that. While there might be some capacitance between the two tape measure bodies (insulated from one another), that rather small capacity can be readily measured with a dipper or AADE L/C Meter and would be less than 50 pFd (based on about 20 pFd measured between a 50-foot measure and a 10-foot measure spaced 1 inch). The author's pressure-pad and paper clamp system for contact seems eminently workable. 7. The article's example uses two Lufkin 100-foot tape measures, apparently new from their appearance, fine chromed finish on the tape measure bodies. That appears to be a fortuitous acquisition by the author and does not reflect any electrical superiority towards Lufkin in this use. Tape measure material is some sort of ferrous alloy picked for flexibility, endurance, relative temperatur stability. To remark that it is "lossy" because it isn't copper, aluminum, silver, or gold or that "someone once wrote that it was lossy" is not using their supposed knowledge of theory (and not being able to use an ohmmeter). Tape measure material has already seen plenty of field radio use in the militaries of the world since the Korean War through Vietnam through Grenada through both Gulf Wars on HF, VHF, UHF. That's a span of nearly 6 decades used in rough environments. The only situation I know where a tape antenna was not desired was in a SID (Seismic Intrusion Device) where field testing indicated a thin wire monopole could be disguised better and less noticeable than a flat tape; the piano wire replacement was more narrowband, a consequence of physical size. A flat tape acts as a "fat conductor" over frequency, creating a slightly wider-bandwidth antenna compared to a single wire version. Direct marking of frequency on antenna elements goes back to at least 1943 and the three-element Yagis of the AN/TRC-1, -3, -4 VHF radio relay sets (70 to 90 MHz). Director, dipole, reflector elements were marked for length v. frequency and channel in white paint on olive drab coating of aluminum tubing elements, plus the director-to-dipole and dipole-to-reflector boom spacings. 73, Len AF6AY | ||
| W4VR | 2007-06-29 | |
|---|---|---|
| RE: Its a DJ8GO Classic!!!! | ||
| During my old Army days back during the Vietnam war we used tape dipoles. As I recall they were calibrated in kHz (or maybe it was kilocycles) and were easy to set up if you knew which frequency you wanted to operate on. The tape dipole was part of a kit that came with our 1 kW General Dynamic SSB radios. Reply to a comment by : KA4KOE on 2007-06-29 I've said it once, I've said it a kabillion times; it ain't an Eham classic....its a DJ8GO classic! KA4KOE Reply to a comment by : W6TH on 2007-06-29 . n2ey Two comments and posts to show your inability to read and understand in common and simple English language. 73, W6TH .: Reply to a comment by : N2EY on 2007-06-29 "...My original post was a comparison was made with a dipole and the tape antennas as the 3 dB loss was the difference between a full size dipole and the tape antenna. The tape antenna was down by 3 dB...Or a -3dB compared to the dipole." Yep - 3 dB less efficient on both transmit and receive. "When a person uses the tape antenna with the -3 dB, the receiving operator on the other end would not know the difference of the -3 dB difference." Without something to compare it to, you're right! All I'm saying is that there are times when 3 dB can make a big difference, and other times when 3 dB makes no difference at all. "As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas, you may have a problem to copy under those circumstances and whereby I would have no problem." Well, you might be surprised at my ability to copy under noise and QRM. But regardless of that, there are certainly times when, if the transmitting station drops their signal 3 dB, the receiving station will have a much harder time copying, if at all. That's my point. "So, By geometric function, I refer to the angle of radiation, which is of utmost importance over the tape antenna with the -3 dB loss." In the shootout, they compared the tape antenna to a wire dipole at the same height. Wouldn't they have the same angle of radiation? "In short term, I prefer a low angle of radiation over any antenna loss of only 3 dB." A low angle of radiation is certainly important for DX. But what if you're not after DX? Say, you want to work a station 300 miles away on 80 meters in the daytime - will a low-angle-only antenna be the best choice? -- It seems to me that the main attractions of the tape antenna are that you can adjust it to any desired length, and *know* the length right away, and that the whole thing rolls up into a package for transport. Aside from that convenience, a simple wire dipole will do the job as well or better. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . N2EY James, You insist on changing the subject as either you do not read well or you do not understand my original post. Give yourself a rest. ...My original post was a comparison was made with a dipole and the tape antennas as the 3 dB loss was the difference between a full size dipole and the tape antenna. The tape antenna was down by 3 dB...Or a -3dB compared to the dipole. When a person uses the tape antenna with the -3 dB, the receiving operator on the other end would not know the difference of the -3 dB difference. As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas, you may have a problem to copy under those circumstances and whereby I would have no problem. So, By geometric function, I refer to the angle of radiation, which is of utmost importance over the tape antenna with the -3 dB loss. In short term, I prefer a low angle of radiation over any antenna loss of only 3 dB. 73, your Elmer W6TH. .: Reply to a comment by : N2EY on 2007-06-28 "N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms." 3 dB is in real engineering terms. ""if your're 30 dB over S9, 3 dB won't make any difference", This I agree." OK so far. The difference between 27 dB over S9 and 30 dB over S9 is trivial. "This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO"." Why don't you agree? If a signal is weak, 3 dB can make a lot of difference. "As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,..." They will if the signal is weak enough. If the signal is just above the noise, and it drops 3 dB, it will then be down in the noise. Depending on the mode and the operator, it may not be copyable. "I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with." Ah - there's the problem! The contact may not be made in the first place if the signal is weak. "............Think............" I did - and I say that under some conditions, 3 dB can make a big difference. *Some* conditions - not all conditions. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms. "if your're 30 dB over S9, 3 dB won't make any difference", This I agree. This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO". As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,... I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with. ............Think............ .: Reply to a comment by : N2EY on 2007-06-28 "I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change." 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. "It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses." The problem was that the tape antenna turned out to be 3 dB less efficient than the reference antenna in the reference direction. That's a big difference, considering that other comparison antennas were as good as the reference dipole. "By geometric function, I refer to the angle of radiation, which is of utmost importance." Yes, it is. And the point is that for the same angle, the tape dipole was 3 dB less efficient. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . . I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change. It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses. By geometric function, I refer to the angle of radiation, which is of utmost importance. 73, W6TH. .: Reply to a comment by : N2FQ on 2007-06-28 Well I got all the parts but have found a) the tape reels do not lock sufficiently to prevent the sag of the tape from pulling more out of the reels b) darn thing is heavy. I think a leather strap locking the two winding pegs might work but haven't bother with it. So now use the Wal-Mart clothesline someone mentioned before. Together with a bnc to post connector at the apex of my pan pole, works very well. I'm considering selling what I purchased, email me (n2fq@sbcglobal.net) if your interested. Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| KA4KOE | 2007-06-29 | |
|---|---|---|
| Its a DJ8GO Classic!!!! | ||
| I've said it once, I've said it a kabillion times; it ain't an Eham classic....its a DJ8GO classic! KA4KOE Reply to a comment by : W6TH on 2007-06-29 . n2ey Two comments and posts to show your inability to read and understand in common and simple English language. 73, W6TH .: Reply to a comment by : N2EY on 2007-06-29 "...My original post was a comparison was made with a dipole and the tape antennas as the 3 dB loss was the difference between a full size dipole and the tape antenna. The tape antenna was down by 3 dB...Or a -3dB compared to the dipole." Yep - 3 dB less efficient on both transmit and receive. "When a person uses the tape antenna with the -3 dB, the receiving operator on the other end would not know the difference of the -3 dB difference." Without something to compare it to, you're right! All I'm saying is that there are times when 3 dB can make a big difference, and other times when 3 dB makes no difference at all. "As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas, you may have a problem to copy under those circumstances and whereby I would have no problem." Well, you might be surprised at my ability to copy under noise and QRM. But regardless of that, there are certainly times when, if the transmitting station drops their signal 3 dB, the receiving station will have a much harder time copying, if at all. That's my point. "So, By geometric function, I refer to the angle of radiation, which is of utmost importance over the tape antenna with the -3 dB loss." In the shootout, they compared the tape antenna to a wire dipole at the same height. Wouldn't they have the same angle of radiation? "In short term, I prefer a low angle of radiation over any antenna loss of only 3 dB." A low angle of radiation is certainly important for DX. But what if you're not after DX? Say, you want to work a station 300 miles away on 80 meters in the daytime - will a low-angle-only antenna be the best choice? -- It seems to me that the main attractions of the tape antenna are that you can adjust it to any desired length, and *know* the length right away, and that the whole thing rolls up into a package for transport. Aside from that convenience, a simple wire dipole will do the job as well or better. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . N2EY James, You insist on changing the subject as either you do not read well or you do not understand my original post. Give yourself a rest. ...My original post was a comparison was made with a dipole and the tape antennas as the 3 dB loss was the difference between a full size dipole and the tape antenna. The tape antenna was down by 3 dB...Or a -3dB compared to the dipole. When a person uses the tape antenna with the -3 dB, the receiving operator on the other end would not know the difference of the -3 dB difference. As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas, you may have a problem to copy under those circumstances and whereby I would have no problem. So, By geometric function, I refer to the angle of radiation, which is of utmost importance over the tape antenna with the -3 dB loss. In short term, I prefer a low angle of radiation over any antenna loss of only 3 dB. 73, your Elmer W6TH. .: Reply to a comment by : N2EY on 2007-06-28 "N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms." 3 dB is in real engineering terms. ""if your're 30 dB over S9, 3 dB won't make any difference", This I agree." OK so far. The difference between 27 dB over S9 and 30 dB over S9 is trivial. "This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO"." Why don't you agree? If a signal is weak, 3 dB can make a lot of difference. "As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,..." They will if the signal is weak enough. If the signal is just above the noise, and it drops 3 dB, it will then be down in the noise. Depending on the mode and the operator, it may not be copyable. "I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with." Ah - there's the problem! The contact may not be made in the first place if the signal is weak. "............Think............" I did - and I say that under some conditions, 3 dB can make a big difference. *Some* conditions - not all conditions. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms. "if your're 30 dB over S9, 3 dB won't make any difference", This I agree. This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO". As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,... I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with. ............Think............ .: Reply to a comment by : N2EY on 2007-06-28 "I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change." 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. "It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses." The problem was that the tape antenna turned out to be 3 dB less efficient than the reference antenna in the reference direction. That's a big difference, considering that other comparison antennas were as good as the reference dipole. "By geometric function, I refer to the angle of radiation, which is of utmost importance." Yes, it is. And the point is that for the same angle, the tape dipole was 3 dB less efficient. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . . I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change. It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses. By geometric function, I refer to the angle of radiation, which is of utmost importance. 73, W6TH. .: Reply to a comment by : N2FQ on 2007-06-28 Well I got all the parts but have found a) the tape reels do not lock sufficiently to prevent the sag of the tape from pulling more out of the reels b) darn thing is heavy. I think a leather strap locking the two winding pegs might work but haven't bother with it. So now use the Wal-Mart clothesline someone mentioned before. Together with a bnc to post connector at the apex of my pan pole, works very well. I'm considering selling what I purchased, email me (n2fq@sbcglobal.net) if your interested. Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| W6TH | 2007-06-29 | |
|---|---|---|
| RE: Tape Dipole -3 dB down. | ||
| . n2ey Two comments and posts to show your inability to read and understand in common and simple English language. 73, W6TH .: Reply to a comment by : N2EY on 2007-06-29 "...My original post was a comparison was made with a dipole and the tape antennas as the 3 dB loss was the difference between a full size dipole and the tape antenna. The tape antenna was down by 3 dB...Or a -3dB compared to the dipole." Yep - 3 dB less efficient on both transmit and receive. "When a person uses the tape antenna with the -3 dB, the receiving operator on the other end would not know the difference of the -3 dB difference." Without something to compare it to, you're right! All I'm saying is that there are times when 3 dB can make a big difference, and other times when 3 dB makes no difference at all. "As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas, you may have a problem to copy under those circumstances and whereby I would have no problem." Well, you might be surprised at my ability to copy under noise and QRM. But regardless of that, there are certainly times when, if the transmitting station drops their signal 3 dB, the receiving station will have a much harder time copying, if at all. That's my point. "So, By geometric function, I refer to the angle of radiation, which is of utmost importance over the tape antenna with the -3 dB loss." In the shootout, they compared the tape antenna to a wire dipole at the same height. Wouldn't they have the same angle of radiation? "In short term, I prefer a low angle of radiation over any antenna loss of only 3 dB." A low angle of radiation is certainly important for DX. But what if you're not after DX? Say, you want to work a station 300 miles away on 80 meters in the daytime - will a low-angle-only antenna be the best choice? -- It seems to me that the main attractions of the tape antenna are that you can adjust it to any desired length, and *know* the length right away, and that the whole thing rolls up into a package for transport. Aside from that convenience, a simple wire dipole will do the job as well or better. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . N2EY James, You insist on changing the subject as either you do not read well or you do not understand my original post. Give yourself a rest. ...My original post was a comparison was made with a dipole and the tape antennas as the 3 dB loss was the difference between a full size dipole and the tape antenna. The tape antenna was down by 3 dB...Or a -3dB compared to the dipole. When a person uses the tape antenna with the -3 dB, the receiving operator on the other end would not know the difference of the -3 dB difference. As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas, you may have a problem to copy under those circumstances and whereby I would have no problem. So, By geometric function, I refer to the angle of radiation, which is of utmost importance over the tape antenna with the -3 dB loss. In short term, I prefer a low angle of radiation over any antenna loss of only 3 dB. 73, your Elmer W6TH. .: Reply to a comment by : N2EY on 2007-06-28 "N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms." 3 dB is in real engineering terms. ""if your're 30 dB over S9, 3 dB won't make any difference", This I agree." OK so far. The difference between 27 dB over S9 and 30 dB over S9 is trivial. "This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO"." Why don't you agree? If a signal is weak, 3 dB can make a lot of difference. "As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,..." They will if the signal is weak enough. If the signal is just above the noise, and it drops 3 dB, it will then be down in the noise. Depending on the mode and the operator, it may not be copyable. "I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with." Ah - there's the problem! The contact may not be made in the first place if the signal is weak. "............Think............" I did - and I say that under some conditions, 3 dB can make a big difference. *Some* conditions - not all conditions. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms. "if your're 30 dB over S9, 3 dB won't make any difference", This I agree. This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO". As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,... I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with. ............Think............ .: Reply to a comment by : N2EY on 2007-06-28 "I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change." 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. "It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses." The problem was that the tape antenna turned out to be 3 dB less efficient than the reference antenna in the reference direction. That's a big difference, considering that other comparison antennas were as good as the reference dipole. "By geometric function, I refer to the angle of radiation, which is of utmost importance." Yes, it is. And the point is that for the same angle, the tape dipole was 3 dB less efficient. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . . I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change. It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses. By geometric function, I refer to the angle of radiation, which is of utmost importance. 73, W6TH. .: Reply to a comment by : N2FQ on 2007-06-28 Well I got all the parts but have found a) the tape reels do not lock sufficiently to prevent the sag of the tape from pulling more out of the reels b) darn thing is heavy. I think a leather strap locking the two winding pegs might work but haven't bother with it. So now use the Wal-Mart clothesline someone mentioned before. Together with a bnc to post connector at the apex of my pan pole, works very well. I'm considering selling what I purchased, email me (n2fq@sbcglobal.net) if your interested. Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| N2EY | 2007-06-29 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| "The most efficient antenna one can use is the end fed halfwave, using the "L" network for resonance." Well, I don't know if it's the *most* efficient antenna one can use. The classic center-fed-halfwave-with-real-open-wire-line-and-balanced-tuner is pretty efficient, too. "However most hams of today do not know how to solve the problems of the radios being hot with rf bites." Sad, isn't it? I learned how to fix that problem as a Novice. "I was happy to find that Icom came out with the AH-4 tuner, although I have never bought or used one as I am still a builder of ham gear." I'm a builder, too. Google my call to see some of my projects. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . KG6QHP The most efficient antenna one can use is the end fed halfwave, using the "L" network for resonance. However most hams of today do not know how to solve the problems of the radios being hot with rf bites. I was happy to find that Icom came out with the AH-4 tuner, although I have never bought or used one as I am still a builder of ham gear. The Tape antenna is a winner and not to be forgotten. .: Reply to a comment by : KG6R on 2007-06-28 All --- I think you can use the same approach except use insulated wire. It is whole lot more flexible than a measuring tape. 73 de KG6R formery kg6qhp, Jim | ||
| N2EY | 2007-06-29 | |
|---|---|---|
| RE: Tape Dipole -3 dB down. | ||
| "...My original post was a comparison was made with a dipole and the tape antennas as the 3 dB loss was the difference between a full size dipole and the tape antenna. The tape antenna was down by 3 dB...Or a -3dB compared to the dipole." Yep - 3 dB less efficient on both transmit and receive. "When a person uses the tape antenna with the -3 dB, the receiving operator on the other end would not know the difference of the -3 dB difference." Without something to compare it to, you're right! All I'm saying is that there are times when 3 dB can make a big difference, and other times when 3 dB makes no difference at all. "As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas, you may have a problem to copy under those circumstances and whereby I would have no problem." Well, you might be surprised at my ability to copy under noise and QRM. But regardless of that, there are certainly times when, if the transmitting station drops their signal 3 dB, the receiving station will have a much harder time copying, if at all. That's my point. "So, By geometric function, I refer to the angle of radiation, which is of utmost importance over the tape antenna with the -3 dB loss." In the shootout, they compared the tape antenna to a wire dipole at the same height. Wouldn't they have the same angle of radiation? "In short term, I prefer a low angle of radiation over any antenna loss of only 3 dB." A low angle of radiation is certainly important for DX. But what if you're not after DX? Say, you want to work a station 300 miles away on 80 meters in the daytime - will a low-angle-only antenna be the best choice? -- It seems to me that the main attractions of the tape antenna are that you can adjust it to any desired length, and *know* the length right away, and that the whole thing rolls up into a package for transport. Aside from that convenience, a simple wire dipole will do the job as well or better. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . N2EY James, You insist on changing the subject as either you do not read well or you do not understand my original post. Give yourself a rest. ...My original post was a comparison was made with a dipole and the tape antennas as the 3 dB loss was the difference between a full size dipole and the tape antenna. The tape antenna was down by 3 dB...Or a -3dB compared to the dipole. When a person uses the tape antenna with the -3 dB, the receiving operator on the other end would not know the difference of the -3 dB difference. As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas, you may have a problem to copy under those circumstances and whereby I would have no problem. So, By geometric function, I refer to the angle of radiation, which is of utmost importance over the tape antenna with the -3 dB loss. In short term, I prefer a low angle of radiation over any antenna loss of only 3 dB. 73, your Elmer W6TH. .: Reply to a comment by : N2EY on 2007-06-28 "N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms." 3 dB is in real engineering terms. ""if your're 30 dB over S9, 3 dB won't make any difference", This I agree." OK so far. The difference between 27 dB over S9 and 30 dB over S9 is trivial. "This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO"." Why don't you agree? If a signal is weak, 3 dB can make a lot of difference. "As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,..." They will if the signal is weak enough. If the signal is just above the noise, and it drops 3 dB, it will then be down in the noise. Depending on the mode and the operator, it may not be copyable. "I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with." Ah - there's the problem! The contact may not be made in the first place if the signal is weak. "............Think............" I did - and I say that under some conditions, 3 dB can make a big difference. *Some* conditions - not all conditions. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms. "if your're 30 dB over S9, 3 dB won't make any difference", This I agree. This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO". As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,... I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with. ............Think............ .: Reply to a comment by : N2EY on 2007-06-28 "I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change." 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. "It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses." The problem was that the tape antenna turned out to be 3 dB less efficient than the reference antenna in the reference direction. That's a big difference, considering that other comparison antennas were as good as the reference dipole. "By geometric function, I refer to the angle of radiation, which is of utmost importance." Yes, it is. And the point is that for the same angle, the tape dipole was 3 dB less efficient. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . . I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change. It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses. By geometric function, I refer to the angle of radiation, which is of utmost importance. 73, W6TH. .: Reply to a comment by : N2FQ on 2007-06-28 Well I got all the parts but have found a) the tape reels do not lock sufficiently to prevent the sag of the tape from pulling more out of the reels b) darn thing is heavy. I think a leather strap locking the two winding pegs might work but haven't bother with it. So now use the Wal-Mart clothesline someone mentioned before. Together with a bnc to post connector at the apex of my pan pole, works very well. I'm considering selling what I purchased, email me (n2fq@sbcglobal.net) if your interested. Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| W6TH | 2007-06-29 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| . KB1ooo, Regarding N2EY's comment about the 3db loss: would an appropriate condition where the 3db loss matters be a signal that is the minimum gain above the noise for which you can have a QSO? Say that's 6db. Then a signal that is 6db above the noise for the reference antenna--for which you could have a QSO--would be a no QSO signal for the other antenna. .................................................. Marc, You also missed the original post point of view. I mentioned that the receiving operator on the end of the tape antenna with the -3 dB loss would never know of such a loss. My concern was to ignore the -3dB tape loss and be more concerned with the use of the angle of radiation; to concentrate more on the geometric function of the antenna height above ground. Which to me is of more importance than to worry of a lossy -3 dB tape antenna. 73, W6TH. Live Free or Die. .: Reply to a comment by : KB1OOO on 2007-06-29 W6TH, Regarding N2EY's comment about the 3db loss: would an appropriate condition where the 3db loss matters be a signal that is the minimum gain above the noise for which you can have a QSO? Say that's 6db. Then a signal that is 6db above the noise for the reference antenna--for which you could have a QSO--would be a no QSO signal for the other antenna. I'm not trying to be rhetorical here, I'm a newbe and happy to be elmered. KB1OOO, Marc Reply to a comment by : W4LGH on 2007-06-29 The problem is that everyone on here has this need to be 100% correct. Even when one is just giving an opinion, there is always someone who wants to tear this opinion down and find all the faults, instead of seeing the good in it. There are a lot of smart people on here. Some with great book sense, some with good common sense and some with great practical experience. Each one of these types of knowledge will net different results, as we know nothing works exactly as the book says, but its a good starting point. Right now the world is full of hate and discontent. Everyone is living on the edge and in fear of being pushed off that edge. There used to be 3 classes in this country, and now there seems to only be 2, the haves and the have nots. The middle class has been just about taxed out of exsistance. We have been forced into being politically correct, when we all know a spade is and will always be a spade. All of this has lead to all the hate and discontent. Because of all the government intervention, our skin has become as thin as an onion. Again, these are my opinions as to why these forums go the way they go. I could be wrong, and am sure someone will say that I am. 73 de W4LGH - Alan http://www.w4lgh.com Reply to a comment by : SSB on 2007-06-29 When are the users of this site going to figure out that these are FORUMS but everybody uses forums as chat rooms in order to insult, scold, ridicule, chastise everybody else. What a bunch of losers. Alex...... | ||
| KC8QFP | 2007-06-29 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| All I can say about this thread is that I hope this antenna ""measures"" up to its expectations!!! I like some of these old ldeas brought back up out of the past. RE: Alan, As for the world going to hell in a hand basket, we do live in a decadent society so to speak, and media has much to do with this demise of fallen civilization as we know it. Entertainment kinda reminds me of the Romans. Sex and violance is everywhere, radio, TV, internet, music, sports, you name it. Look what all this crap is doing to the minds of the kids! They aren't very interested in ham radio when they have celleryfones that text and play beebop rap crap, and video games. Shoot, I can't ewven watch something on TV without somebody being killed or having some kinky mooshy sex scenes. Ozzie and Hariot are history as well as Leave it to Beaver. Now we have Ozzie's @#$%^& house and Horney Housewives or the Sopranoes. YIPPIE! Let's all party -- whilst the Titanic sinks into the night! (That is unless you are on Noah's Ark instead -- if you get the matephor)! I think thhis is the result of many many people NOT believing the Holy Bible. Most are clueless about the ten commandments - merely a few verses in the Bible, lot's of good stuff in there, if people would only look! But they'd rather watch TV. The result is... all around us. Reply to a comment by : W4LGH on 2007-06-29 The problem is that everyone on here has this need to be 100% correct. Even when one is just giving an opinion, there is always someone who wants to tear this opinion down and find all the faults, instead of seeing the good in it. There are a lot of smart people on here. Some with great book sense, some with good common sense and some with great practical experience. Each one of these types of knowledge will net different results, as we know nothing works exactly as the book says, but its a good starting point. Right now the world is full of hate and discontent. Everyone is living on the edge and in fear of being pushed off that edge. There used to be 3 classes in this country, and now there seems to only be 2, the haves and the have nots. The middle class has been just about taxed out of exsistance. We have been forced into being politically correct, when we all know a spade is and will always be a spade. All of this has lead to all the hate and discontent. Because of all the government intervention, our skin has become as thin as an onion. Again, these are my opinions as to why these forums go the way they go. I could be wrong, and am sure someone will say that I am. 73 de W4LGH - Alan http://www.w4lgh.com Reply to a comment by : SSB on 2007-06-29 When are the users of this site going to figure out that these are FORUMS but everybody uses forums as chat rooms in order to insult, scold, ridicule, chastise everybody else. What a bunch of losers. Alex...... | ||
| KB1OOO | 2007-06-29 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| W6TH, Regarding N2EY's comment about the 3db loss: would an appropriate condition where the 3db loss matters be a signal that is the minimum gain above the noise for which you can have a QSO? Say that's 6db. Then a signal that is 6db above the noise for the reference antenna--for which you could have a QSO--would be a no QSO signal for the other antenna. I'm not trying to be rhetorical here, I'm a newbe and happy to be elmered. KB1OOO, Marc Reply to a comment by : W4LGH on 2007-06-29 The problem is that everyone on here has this need to be 100% correct. Even when one is just giving an opinion, there is always someone who wants to tear this opinion down and find all the faults, instead of seeing the good in it. There are a lot of smart people on here. Some with great book sense, some with good common sense and some with great practical experience. Each one of these types of knowledge will net different results, as we know nothing works exactly as the book says, but its a good starting point. Right now the world is full of hate and discontent. Everyone is living on the edge and in fear of being pushed off that edge. There used to be 3 classes in this country, and now there seems to only be 2, the haves and the have nots. The middle class has been just about taxed out of exsistance. We have been forced into being politically correct, when we all know a spade is and will always be a spade. All of this has lead to all the hate and discontent. Because of all the government intervention, our skin has become as thin as an onion. Again, these are my opinions as to why these forums go the way they go. I could be wrong, and am sure someone will say that I am. 73 de W4LGH - Alan http://www.w4lgh.com Reply to a comment by : SSB on 2007-06-29 When are the users of this site going to figure out that these are FORUMS but everybody uses forums as chat rooms in order to insult, scold, ridicule, chastise everybody else. What a bunch of losers. Alex...... | ||
| W4LGH | 2007-06-29 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| The problem is that everyone on here has this need to be 100% correct. Even when one is just giving an opinion, there is always someone who wants to tear this opinion down and find all the faults, instead of seeing the good in it. There are a lot of smart people on here. Some with great book sense, some with good common sense and some with great practical experience. Each one of these types of knowledge will net different results, as we know nothing works exactly as the book says, but its a good starting point. Right now the world is full of hate and discontent. Everyone is living on the edge and in fear of being pushed off that edge. There used to be 3 classes in this country, and now there seems to only be 2, the haves and the have nots. The middle class has been just about taxed out of exsistance. We have been forced into being politically correct, when we all know a spade is and will always be a spade. All of this has lead to all the hate and discontent. Because of all the government intervention, our skin has become as thin as an onion. Again, these are my opinions as to why these forums go the way they go. I could be wrong, and am sure someone will say that I am. 73 de W4LGH - Alan http://www.w4lgh.com Reply to a comment by : SSB on 2007-06-29 When are the users of this site going to figure out that these are FORUMS but everybody uses forums as chat rooms in order to insult, scold, ridicule, chastise everybody else. What a bunch of losers. Alex...... | ||
| SSB | 2007-06-29 | |
|---|---|---|
| Reinventing the Tape Dipole | ||
| When are the users of this site going to figure out that these are FORUMS but everybody uses forums as chat rooms in order to insult, scold, ridicule, chastise everybody else. What a bunch of losers. Alex...... | ||
| W6TH | 2007-06-28 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| . KX8N on June 28, 2007 "As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas,... " Oh boy. .................................................... David,kx8n, you as a Vanity Extra class (5 wpm free loader), may I say?.......Oh Boy....... .: Reply to a comment by : K8NWX on 2007-06-28 "As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas,... " Oh boy. Reply to a comment by : K7NNG on 2007-06-28 AI2AI..............You made comments that prove you know little about antennas, and have forgotten(or never knew,) experimenting is ham radio. Just go away man. | ||
| NXET | 2007-06-28 | |
|---|---|---|
| RE: KA5S Tape Dipole | ||
| this is a lot like microsofts NT program. It stood for Nice TRY. While the design looks simple, its not. First off its HEAVY. what are you going to haul this thing up in the sky with? You can't hold it between two trees it way heavy with the steel tapes?? Second, as Alen said NO BALUN Third, The roll of tape still in the case does something magic to the rest of the signal. Forth, Stainless steel is not a good antenna no matter what others say. Ask Cebik about Stainless steel antennas. Copper is much better (some of the other designs on this web are better suited to antennas than this one) we won't even talk about the expense of building one. Years ago, we did a lot of work on the Hygain H-4000 along with Collins TD-1a which was the same thing. Now you know why they quit selling them. Their were better cheaper dipole configurations out their that worked rings around this thing. (weight being the real killer when you also added the coax hanging down you needed a heavy duty crane to keep it up in the sky. If you want a simple homemade one may I suggest the one that was made for HF (Reel Type Portable Antenna-- by Marvin Hamilton (K9GDV) on April 9, 2004,-- on this web) or the Hygain, DP-19PD. Simple and easy to make with better results, lighter weight too. Have fun no matter what antenna you put up. Remeber getting it up is half the fun. keeping it up--well Reply to a comment by : VA3SAX on 2007-06-28 it's an interesting article but you don't give much in the way of detail of exactly how each part was done Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| AI2IA | 2007-06-28 | |
|---|---|---|
| Reinventing the AI2IA. | ||
| A reminder to NY7Q, the writer of this profound message: "AI2AI..............You made comments that prove you know little about antennas, and have forgotten(or never knew,) experimenting is ham radio. Just go away man." Thank you for the compliment. As a subscriber to eHam.net, you will see my posts on here as often as I choose. Who are you to tell me to go away? What are your "qualifications"? The truth is that you benefit from my posts very much, since they are always on your mind. I'm glad that I disturb you. "I have forgotten (or never knew,) experimenting is ham radio," eh? Now that's an amusing comment! By the way, dummy, my call is AI2IA, not AI2AI. It looks like there are a lot of things you can't get straight. | ||
| K8NWX | 2007-06-28 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| "As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas,... " Oh boy. Reply to a comment by : K7NNG on 2007-06-28 AI2AI..............You made comments that prove you know little about antennas, and have forgotten(or never knew,) experimenting is ham radio. Just go away man. | ||
| K7NNG | 2007-06-28 | |
|---|---|---|
| Reinventing the Tape Dipole | ||
| AI2AI..............You made comments that prove you know little about antennas, and have forgotten(or never knew,) experimenting is ham radio. Just go away man. | ||
| K7NNG | 2007-06-28 | |
|---|---|---|
| Reinventing the Tape Dipole | ||
| I use a YOYO and I like it very much. In fact it is hanging in the trees right now on 20m and 40 m.. For stations close in it works great, and I work the east coast on 20 no problem... | ||
| W6TH | 2007-06-28 | |
|---|---|---|
| RE: Reinventing the Tape Dipole | ||
| . KG6QHP The most efficient antenna one can use is the end fed halfwave, using the "L" network for resonance. However most hams of today do not know how to solve the problems of the radios being hot with rf bites. I was happy to find that Icom came out with the AH-4 tuner, although I have never bought or used one as I am still a builder of ham gear. The Tape antenna is a winner and not to be forgotten. .: Reply to a comment by : KG6R on 2007-06-28 All --- I think you can use the same approach except use insulated wire. It is whole lot more flexible than a measuring tape. 73 de KG6R formery kg6qhp, Jim | ||
| W6TH | 2007-06-28 | |
|---|---|---|
| RE: Tape Dipole -3 dB down. | ||
| . N2EY James, You insist on changing the subject as either you do not read well or you do not understand my original post. Give yourself a rest. ...My original post was a comparison was made with a dipole and the tape antennas as the 3 dB loss was the difference between a full size dipole and the tape antenna. The tape antenna was down by 3 dB...Or a -3dB compared to the dipole. When a person uses the tape antenna with the -3 dB, the receiving operator on the other end would not know the difference of the -3 dB difference. As far as a copy with noise and qrm, I can assure that I have been more trained with this situation than you, whereas, you may have a problem to copy under those circumstances and whereby I would have no problem. So, By geometric function, I refer to the angle of radiation, which is of utmost importance over the tape antenna with the -3 dB loss. In short term, I prefer a low angle of radiation over any antenna loss of only 3 dB. 73, your Elmer W6TH. .: Reply to a comment by : N2EY on 2007-06-28 "N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms." 3 dB is in real engineering terms. ""if your're 30 dB over S9, 3 dB won't make any difference", This I agree." OK so far. The difference between 27 dB over S9 and 30 dB over S9 is trivial. "This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO"." Why don't you agree? If a signal is weak, 3 dB can make a lot of difference. "As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,..." They will if the signal is weak enough. If the signal is just above the noise, and it drops 3 dB, it will then be down in the noise. Depending on the mode and the operator, it may not be copyable. "I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with." Ah - there's the problem! The contact may not be made in the first place if the signal is weak. "............Think............" I did - and I say that under some conditions, 3 dB can make a big difference. *Some* conditions - not all conditions. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms. "if your're 30 dB over S9, 3 dB won't make any difference", This I agree. This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO". As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,... I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with. ............Think............ .: Reply to a comment by : N2EY on 2007-06-28 "I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change." 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. "It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses." The problem was that the tape antenna turned out to be 3 dB less efficient than the reference antenna in the reference direction. That's a big difference, considering that other comparison antennas were as good as the reference dipole. "By geometric function, I refer to the angle of radiation, which is of utmost importance." Yes, it is. And the point is that for the same angle, the tape dipole was 3 dB less efficient. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . . I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change. It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses. By geometric function, I refer to the angle of radiation, which is of utmost importance. 73, W6TH. .: Reply to a comment by : N2FQ on 2007-06-28 Well I got all the parts but have found a) the tape reels do not lock sufficiently to prevent the sag of the tape from pulling more out of the reels b) darn thing is heavy. I think a leather strap locking the two winding pegs might work but haven't bother with it. So now use the Wal-Mart clothesline someone mentioned before. Together with a bnc to post connector at the apex of my pan pole, works very well. I'm considering selling what I purchased, email me (n2fq@sbcglobal.net) if your interested. Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| KG6R | 2007-06-28 | |
|---|---|---|
| Reinventing the Tape Dipole | ||
| All --- I think you can use the same approach except use insulated wire. It is whole lot more flexible than a measuring tape. 73 de KG6R formery kg6qhp, Jim | ||
| N2EY | 2007-06-28 | |
|---|---|---|
| RE: KA5S Tape Dipole | ||
| "N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms." 3 dB is in real engineering terms. ""if your're 30 dB over S9, 3 dB won't make any difference", This I agree." OK so far. The difference between 27 dB over S9 and 30 dB over S9 is trivial. "This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO"." Why don't you agree? If a signal is weak, 3 dB can make a lot of difference. "As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,..." They will if the signal is weak enough. If the signal is just above the noise, and it drops 3 dB, it will then be down in the noise. Depending on the mode and the operator, it may not be copyable. "I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with." Ah - there's the problem! The contact may not be made in the first place if the signal is weak. "............Think............" I did - and I say that under some conditions, 3 dB can make a big difference. *Some* conditions - not all conditions. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms. "if your're 30 dB over S9, 3 dB won't make any difference", This I agree. This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO". As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,... I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with. ............Think............ .: Reply to a comment by : N2EY on 2007-06-28 "I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change." 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. "It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses." The problem was that the tape antenna turned out to be 3 dB less efficient than the reference antenna in the reference direction. That's a big difference, considering that other comparison antennas were as good as the reference dipole. "By geometric function, I refer to the angle of radiation, which is of utmost importance." Yes, it is. And the point is that for the same angle, the tape dipole was 3 dB less efficient. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . . I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change. It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses. By geometric function, I refer to the angle of radiation, which is of utmost importance. 73, W6TH. .: Reply to a comment by : N2FQ on 2007-06-28 Well I got all the parts but have found a) the tape reels do not lock sufficiently to prevent the sag of the tape from pulling more out of the reels b) darn thing is heavy. I think a leather strap locking the two winding pegs might work but haven't bother with it. So now use the Wal-Mart clothesline someone mentioned before. Together with a bnc to post connector at the apex of my pan pole, works very well. I'm considering selling what I purchased, email me (n2fq@sbcglobal.net) if your interested. Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| W6TH | 2007-06-28 | |
|---|---|---|
| RE: KA5S Tape Dipole | ||
| . N2EY James said the following, 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. ................................................... James, you are trying to confuse the readers, what you say is in ham radio terms not in real engineering terms. "if your're 30 dB over S9, 3 dB won't make any difference", This I agree. This I don't agree: "but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO". As I mentioned. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the antenna 3dB loss,... I am sure you will not detect the difference of a 3 dB loss on a radiating antenna system, after your contact was made with the antenna loss of 3 dB to start with. ............Think............ .: Reply to a comment by : N2EY on 2007-06-28 "I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change." 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. "It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses." The problem was that the tape antenna turned out to be 3 dB less efficient than the reference antenna in the reference direction. That's a big difference, considering that other comparison antennas were as good as the reference dipole. "By geometric function, I refer to the angle of radiation, which is of utmost importance." Yes, it is. And the point is that for the same angle, the tape dipole was 3 dB less efficient. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . . I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change. It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses. By geometric function, I refer to the angle of radiation, which is of utmost importance. 73, W6TH. .: Reply to a comment by : N2FQ on 2007-06-28 Well I got all the parts but have found a) the tape reels do not lock sufficiently to prevent the sag of the tape from pulling more out of the reels b) darn thing is heavy. I think a leather strap locking the two winding pegs might work but haven't bother with it. So now use the Wal-Mart clothesline someone mentioned before. Together with a bnc to post connector at the apex of my pan pole, works very well. I'm considering selling what I purchased, email me (n2fq@sbcglobal.net) if your interested. Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| AC7NA | 2007-06-28 | |
|---|---|---|
| RE: Make a Copper Wire Dipole | ||
| My approach is to use a couple old fly reels (bought at a yard sale for $5) spooled up with light gauge insulated wire. Like another poster mentioned, I place the reels at each end to keep the weight down at the center insulator...I don't even use end insulators, I just tie the ends off with a single pass through the perforations in the reel side plates and another wrap around the rod seat and it works fine. The rod seats also make it easy to lash the reels to nearly anything. It is also very lightweight in comparison and certainly backpack"able". Brian AC7NA Reply to a comment by : AI2IA on 2007-06-28 In my opinion, these sort of gadgets are junk. Copper wire is abundant. Make your portable antennas out of wire, and spend a few bucks on a balun and good insulators. You will get far better operation and enjoyment out of this approach. Make the best solder joints possible, and you will have a good portable antenna that will last years. Make a neat wire holder out of plastic or light wood, too! | ||
| WA8MEA | 2007-06-28 | |
|---|---|---|
| Reinventing the Tape Dipole | ||
| There is an oddball from Australia who, for some strange reason, likes to put down antennas like the authors...along with the type my company makes. I am not sure what his purpose is. Neither the author, nor I, nor any other maker of portable antennas such as these has EVER made any spectacular or outrageous claims of superior performance. These antennas are simply antennas of portability, convenience and uniqueness. Jealousy? Not sure. The guy is an SWL. Not sure if he's a ham. I know a lot of SWL's like to tout radio knowledge without benefit of a ham license. I dare say some are smarter than hams. But generally, the guys with the ham licenses have a better grasp of radio theory. For some reason this anonymous know-it-all has been able to wiggle his way into Wikipedia. (That in itself outta reveal a lot about his credibility.) But here's his website and e-mail: Onegammyleg@Yahoo.com.au http://www.swdxer.co.nr/ 73, Bill - WA8MEA http://HamRadioFun.com | ||
| AI2IA | 2007-06-28 | |
|---|---|---|
| Make a Copper Wire Dipole | ||
| In my opinion, these sort of gadgets are junk. Copper wire is abundant. Make your portable antennas out of wire, and spend a few bucks on a balun and good insulators. You will get far better operation and enjoyment out of this approach. Make the best solder joints possible, and you will have a good portable antenna that will last years. Make a neat wire holder out of plastic or light wood, too! | ||
| N2EY | 2007-06-28 | |
|---|---|---|
| RE: KA5S Tape Dipole | ||
| "I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change." 3 dB is half the power. Whether that makes a difference depends on the situation - if your're 30 dB over S9, 3 dB won't make any difference, but if you're close to the noise level or QRM level, 3 dB can be the difference between a QSO and no QSO. "It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses." The problem was that the tape antenna turned out to be 3 dB less efficient than the reference antenna in the reference direction. That's a big difference, considering that other comparison antennas were as good as the reference dipole. "By geometric function, I refer to the angle of radiation, which is of utmost importance." Yes, it is. And the point is that for the same angle, the tape dipole was 3 dB less efficient. 73 de Jim, N2EY Reply to a comment by : W6TH on 2007-06-28 . . I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change. It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses. By geometric function, I refer to the angle of radiation, which is of utmost importance. 73, W6TH. .: Reply to a comment by : N2FQ on 2007-06-28 Well I got all the parts but have found a) the tape reels do not lock sufficiently to prevent the sag of the tape from pulling more out of the reels b) darn thing is heavy. I think a leather strap locking the two winding pegs might work but haven't bother with it. So now use the Wal-Mart clothesline someone mentioned before. Together with a bnc to post connector at the apex of my pan pole, works very well. I'm considering selling what I purchased, email me (n2fq@sbcglobal.net) if your interested. Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| KX0R | 2007-06-28 | |
|---|---|---|
| Reinventing the Tape Dipole | ||
| This looks like a nice tape dipole you could build yourself with available materials. It looks strong and reliable, and it could be used in many situations. A balun could be added easily, perhaps just clipped on with a little carabiner and connected with a short coax cable. The point about the losses in the shootout test is worth pursuing, because we wouldn't expect to see more than maybe 0.5 to 1 db loss due to the conductor loss of the tape, especially at low frequencies. One possible problem is that the part of the tape that is rolled up inside the housings forms a coiled inductor. Since the tapes are insulated with some coating, the turns don't short, but there would be a lot of capacitance between the turns. It's likely that there might be some resonant modes where these coils would "suck out" some power and dissipate it, especially since the material has more resistance than copper. A very similar problem happens in tuners, including some I've built, with bandswitches used to switch taps on the inductors. The unused turns can self-resonate and suck power out when the tuner is used on certain higher frequencies. If the switch shorts out the unused turns, that usually helps, but resonances can occur in large coils anyhow. One easy test with the tape dipole would be to use jumpers to short out the unused tape in the housings - if the impedance changes much, it would indicate resonant activity and possible extra loss in the coiled tapes. Tests could be done with an SWR analyzer at low power. One plus of this tape dipole is that it looks like it could handle at least 100 watts with no problem. It's overkill for QRP. For QRP, a simple dipole antenna made with dark-colored insulated copper wire is smaller to pack, much lighter, and less visible when up. A small balanced tuner (like a BLT, from Hendricks QRP kits http://www.qrpkits.com/index.html ) would enable tuning on several bands, and it weighs much less than one of the tape units here. 300-ohm TV line permits convenient balanced multiband feed with less loss than small coax. I do a fair bit of camping/QRP/portable operation, and this is the type of setup I favor. Minimizing the weight at the center feedpoint is often important when you use trees or other temporary supports. This tape dipole has a very heavy center unit, so it would probably require its own support. Using a lot of tension on this dipole is probably not practical, because the tapes might slip. However, if you're going to run some power, this tape antenna might mean you need no tuner at all, especially if you use a balun and perhaps play around with the tape lengths, feedline length, and height of the system. If you want to run the tape antenna shown here on 75/80M, it might be more practical to add 15 to 20 foot wire extensions to each tape to enable resonance than to use larger tape reels, unless 80M operation is your priority. Two 100 foot reels would be very heavy. It's amazing how small, light, and convenient a rolled-up 135-foot dipole made of #18 stranded insulated wire is. Even with 50 feet of 300 ohm twinlead it's not heavy. Personal preference is really important for portable operation, because getting on the air in a remote place can be very demanding. Every situation is different, and we need a lot of skills and tricks to be successful. What works for me might not work for you, etc. The main thing is to go out portable often, practice your skills, and keep improving your tools. I've learned a lot from my disasters and frustrations! | ||
| KB4IJ | 2007-06-28 | |
|---|---|---|
| Reinventing the Tape Dipole | ||
| My tape dipole uses 2 100' steel tapes with the reels on the outboard end, thus reducing the weight and wind area at the top of a light weight pole. I use it as a NVIS antenna for state and regional nets and put it up in an inverted Vee configuration. This makes it easy to set exact lengths using the tape measurement indications. The coiled reels seem to act as a capacitance hat, slightly lowering the resonant frequency. (Each leg is set about 222/f Mhz vs. the more common 234/f Mhz formula). It is through a balun. I've been vary happy with the results. Bill KB4IJ | ||
| W6TH | 2007-06-28 | |
|---|---|---|
| RE: KA5S Tape Dipole | ||
| . . I don't understand of most hams worrying about loss, especially a 3dB loss. A 3dB loss to my receiver will hardly be noticed, as my ears won't detect the loss, but if it were 6dB loss, I am sure I will notice the change. It is much better to indicate how the output is related to the input of any antenna or antenna system. Try working out the geometric function and not be so concerned with dB losses. By geometric function, I refer to the angle of radiation, which is of utmost importance. 73, W6TH. .: Reply to a comment by : N2FQ on 2007-06-28 Well I got all the parts but have found a) the tape reels do not lock sufficiently to prevent the sag of the tape from pulling more out of the reels b) darn thing is heavy. I think a leather strap locking the two winding pegs might work but haven't bother with it. So now use the Wal-Mart clothesline someone mentioned before. Together with a bnc to post connector at the apex of my pan pole, works very well. I'm considering selling what I purchased, email me (n2fq@sbcglobal.net) if your interested. Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| N8KOM | 2007-06-28 | |
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| Reinventing the Tape Dipole | ||
| Nice to see this design re-visited. I agree with the comments that more details on this specific holder implementation would be nice. One area or detail to consider is that the tape may actually conduct through the case of the tape measure if the case is metal. That makes mounting the two tapes back to back or side to side tricky. 73 - Steve | ||
| N2FQ | 2007-06-28 | |
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| RE: KA5S Tape Dipole | ||
| Well I got all the parts but have found a) the tape reels do not lock sufficiently to prevent the sag of the tape from pulling more out of the reels b) darn thing is heavy. I think a leather strap locking the two winding pegs might work but haven't bother with it. So now use the Wal-Mart clothesline someone mentioned before. Together with a bnc to post connector at the apex of my pan pole, works very well. I'm considering selling what I purchased, email me (n2fq@sbcglobal.net) if your interested. Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| W6TH | 2007-06-28 | |
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| RE: KA5S Tape Dipole | ||
| . One of the best repeat articles I read on eHAM. This chap Ulrich H. Steinberg, DJ8GO is a rocket scientist, a true ham with the true ham spirit. Congratulations Ulrich, go to the head of the class. 73, W6TH .: Reply to a comment by : KB2FCV on 2007-06-28 That looks like some pretty hefty construction! Very nice handiwork. My portable dipole consists of two of those walmart plastic portable clothesline cases with 33 or so feet of wire in each. A center insulator with a few terminals completes the antenna. The entire antenna fits in a ziplock sandwich bag (not including the feedline). Reply to a comment by : K0BG on 2007-06-28 When I see a buddie pole out perform a reference dipole, I question the validity of the shootout. Further, there is nothing about the tape dipole which would cause it to be 3 dB down from a reference one. Yet another reason I'd doubt the validity of the shootout. The only addition which might makes things a little better is a balun. The DIY article published in QST did include one in its construction. Alan, KØBG www.k0bg.com Reply to a comment by : N3VMD on 2007-06-28 "it's an interesting article but you don't give much in the way of detail of exactly how each part was done" Seems simple enough to me, given the quality pics and the simplistic nature of a dipole whats left to figure out? Todd N3VMD Reply to a comment by : VA3SAX on 2007-06-28 it's an interesting article but you don't give much in the way of detail of exactly how each part was done Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| N2EY | 2007-06-28 | |
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| RE: KA5S Tape Dipole | ||
| "Further, there is nothing about the tape dipole which would cause it to be 3 dB down from a reference one." I can think of two things: First, the tape conductivity at RF may not be very good compared to copper or aluminum. Particularly on 80/75 meters, where the antenna is over 100 feet long and relatively low Z because it is close to the ground in terms of wavelengths, there may be significant loss in the tapes. Second, the two reels and the supporting frame may place a considerable capacitance across the feedpoint. This capacitance may be tuned out by adjusting the antenna length, but it may not be low-loss. My money is on the first cause. I recall an article in 'ham radio' many years ago where a simple 80/75 inverted V with four legs achieved low SWR from 3.5 to 4.0 MHz. The trick was that the antenna was made with steel wire, and the RF resistance of the wire was so high that it lowered the SWR at the band edges. That it also lowered the efficiency was kinda ignored. 73 de Jim, N2EY Reply to a comment by : K0BG on 2007-06-28 When I see a buddie pole out perform a reference dipole, I question the validity of the shootout. Further, there is nothing about the tape dipole which would cause it to be 3 dB down from a reference one. Yet another reason I'd doubt the validity of the shootout. The only addition which might makes things a little better is a balun. The DIY article published in QST did include one in its construction. Alan, KØBG www.k0bg.com Reply to a comment by : N3VMD on 2007-06-28 "it's an interesting article but you don't give much in the way of detail of exactly how each part was done" Seems simple enough to me, given the quality pics and the simplistic nature of a dipole whats left to figure out? Todd N3VMD Reply to a comment by : VA3SAX on 2007-06-28 it's an interesting article but you don't give much in the way of detail of exactly how each part was done Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| N2EY | 2007-06-28 | |
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| RE: KA5S Tape Dipole | ||
| "Further, there is nothing about the tape dipole which would cause it to be 3 dB down from a reference one." I can think of two things: First, the tape conductivity at RF may not be very good compared to copper or aluminum. Particularly on 80/75 meters, where the antenna is over 100 feet long and relatively low Z because it is close to the ground in terms of wavelengths, there may be significant loss in the tapes. Second, the two reels and the supporting frame may place a considerable capacitance across the feedpoint. This capacitance may be tuned out by adjusting the antenna length, but it may not be low-loss. My money is on the first cause. I recall an article in 'ham radio' many years ago where a simple 80/75 inverted V with four legs achieved low SWR from 3.5 to 4.0 MHz. The trick was that the antenna was made with steel wire, and the RF resistance of the wire was so high that it lowered the SWR at the band edges. That it also lowered the efficiency was kinda ignored. 73 de Jim, N2EY Reply to a comment by : K0BG on 2007-06-28 When I see a buddie pole out perform a reference dipole, I question the validity of the shootout. Further, there is nothing about the tape dipole which would cause it to be 3 dB down from a reference one. Yet another reason I'd doubt the validity of the shootout. The only addition which might makes things a little better is a balun. The DIY article published in QST did include one in its construction. Alan, KØBG www.k0bg.com Reply to a comment by : N3VMD on 2007-06-28 "it's an interesting article but you don't give much in the way of detail of exactly how each part was done" Seems simple enough to me, given the quality pics and the simplistic nature of a dipole whats left to figure out? Todd N3VMD Reply to a comment by : VA3SAX on 2007-06-28 it's an interesting article but you don't give much in the way of detail of exactly how each part was done Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| KB2FCV | 2007-06-28 | |
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| RE: KA5S Tape Dipole | ||
| That looks like some pretty hefty construction! Very nice handiwork. My portable dipole consists of two of those walmart plastic portable clothesline cases with 33 or so feet of wire in each. A center insulator with a few terminals completes the antenna. The entire antenna fits in a ziplock sandwich bag (not including the feedline). Reply to a comment by : K0BG on 2007-06-28 When I see a buddie pole out perform a reference dipole, I question the validity of the shootout. Further, there is nothing about the tape dipole which would cause it to be 3 dB down from a reference one. Yet another reason I'd doubt the validity of the shootout. The only addition which might makes things a little better is a balun. The DIY article published in QST did include one in its construction. Alan, KØBG www.k0bg.com Reply to a comment by : N3VMD on 2007-06-28 "it's an interesting article but you don't give much in the way of detail of exactly how each part was done" Seems simple enough to me, given the quality pics and the simplistic nature of a dipole whats left to figure out? Todd N3VMD Reply to a comment by : VA3SAX on 2007-06-28 it's an interesting article but you don't give much in the way of detail of exactly how each part was done Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| W4LGH | 2007-06-28 | |
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| RE: KA5S Tape Dipole | ||
| There is nothing wrong with the tape line dipole. They work very well, and can be GREAT for a portable or emergency antenna. I particularly like the way the aurthor connects to it. Some try to make a connection to the center of the reels, and this can cause some problems. They can also be a little on the heavy side, depending or what brand and size of the tape lines. Another good idea out there was the YOYO antenna, which is the same principle. Owned one of these and donated it to an Emergency Communications trailer we had. It was mounted atop of a 33' light weight push up pole. Just spool off what band you wanted and push the pole up. Worked great. The people who make the YOYO are still out there and are located at: http://www.hamradiofun.com/ Very inexpensive, light weight, and easy to use. Every emergency pack should have one in it. And NO I do not work for them, just a neat product. 73 de W4LGH - Alan http://www.w4lgh.com Reply to a comment by : K0BG on 2007-06-28 When I see a buddie pole out perform a reference dipole, I question the validity of the shootout. Further, there is nothing about the tape dipole which would cause it to be 3 dB down from a reference one. Yet another reason I'd doubt the validity of the shootout. The only addition which might makes things a little better is a balun. The DIY article published in QST did include one in its construction. Alan, KØBG www.k0bg.com Reply to a comment by : N3VMD on 2007-06-28 "it's an interesting article but you don't give much in the way of detail of exactly how each part was done" Seems simple enough to me, given the quality pics and the simplistic nature of a dipole whats left to figure out? Todd N3VMD Reply to a comment by : VA3SAX on 2007-06-28 it's an interesting article but you don't give much in the way of detail of exactly how each part was done Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| K0BG | 2007-06-28 | |
|---|---|---|
| RE: KA5S Tape Dipole | ||
| When I see a buddie pole out perform a reference dipole, I question the validity of the shootout. Further, there is nothing about the tape dipole which would cause it to be 3 dB down from a reference one. Yet another reason I'd doubt the validity of the shootout. The only addition which might makes things a little better is a balun. The DIY article published in QST did include one in its construction. Alan, KØBG www.k0bg.com Reply to a comment by : N3VMD on 2007-06-28 "it's an interesting article but you don't give much in the way of detail of exactly how each part was done" Seems simple enough to me, given the quality pics and the simplistic nature of a dipole whats left to figure out? Todd N3VMD Reply to a comment by : VA3SAX on 2007-06-28 it's an interesting article but you don't give much in the way of detail of exactly how each part was done Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| N3VMD | 2007-06-28 | |
|---|---|---|
| RE: KA5S Tape Dipole | ||
| "it's an interesting article but you don't give much in the way of detail of exactly how each part was done" Seems simple enough to me, given the quality pics and the simplistic nature of a dipole whats left to figure out? Todd N3VMD Reply to a comment by : VA3SAX on 2007-06-28 it's an interesting article but you don't give much in the way of detail of exactly how each part was done Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| VA3SAX | 2007-06-28 | |
|---|---|---|
| RE: KA5S Tape Dipole | ||
| it's an interesting article but you don't give much in the way of detail of exactly how each part was done Reply to a comment by : KQ6XA on 2007-06-28 Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
| KQ6XA | 2007-06-28 | |
|---|---|---|
| KA5S Tape Dipole | ||
| Cortland KA5S made a tape measure inverted-V dipole with similar tape reels, but with both the two reels stacked flat (pancake format). He entered his antenna in the HFpack Antenna Shootout (horizontal polarization). The antenna measured on 14MHz about -3dB down from the reference dipole. Possibly some RF was absorbed by the reels. More information: http://www.hfpack.com/antennas/shootouthorizontal2002.html 73 Bonnie KQ6XA . | ||
