Small EH Antenna
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KE0VH
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August 19, 2002
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We all have antenna "issues" of some sort. Be it small lots, apartment dwelling, non-ham spouses who do not think that a 50 foot tower and triband beam are not things of beauty. And, by nature, most of us hams love to experiment. And, I am also a broadcast radio engineer, so antennas for me are something of great interest as I have had the opportunity to play with directional AM arrays and 50 kW transmitters. But, with all that said, while having room for antenna's, my family is not very receptive to towers or RFI or wires all over the yard. Dipoles hidden in a tree are adequate, but performance at 12 to 15 feet above ground could be much better, and a 40-meter wraparound dipole through the trees and terminating in a twist in the garage leave a lot to be desired. A 10-meter vertical dipole works well, but of course when 10 is open you can work the world on a wet noodle. However, there is no directivity to it, and sometimes the bigger stations (even those with monoband 3 element yagi's) make my signal sound like I am using a wet noodle. And, ever problematic is RFI in the TV's, VCR's and the next-door neighbors house only 20 feet away from the dipoles. So, how do you solve all those problems with minimal time and still have effective and even more than effective antennas? Pretty insurmountable or so it would seem.
But, we have ways to make the antenna's talk. Maybe you have read or heard about the CFA antenna's being tested in Egypt and the UK. What are CFA's? Crossed field antennas. Only 2% of a wavelength in size, nearly 100% efficiency, setting up the electric and magnetic fields in a much different way. That’s right. And one of the benefits of the way the fields are set up is that EMI is virtually eliminated.
I didn't typo here. And, as a broadcast engineer I think a 500 foot radiator (or 160 feet, or yagi’s, towers and the like ) is a thing of beauty, and you should have at least a quarter wave vertical with a good ground system to radiate properly, setting up the electric and magnetic fields according to how Mr. Hertz back in the 1880's developed the basic antenna we all have used. All these details can be found by going to the www.eh-antenna.com site. Far more detail and explanation than I will put here, so check out the site to find out more. Also, Jack, W0KPH has done a lot of work with the EH types of antenna's (very successfully). Go to http://www.qsl.net/w0kph/ I have talked with Jack at length and am very excited about the design.
To that end, I constructed w0kph's 20-meter antenna and tested it out. Fellow amateurs: I was as amazed as you are about to be. My test antenna was made out of a cardboard mailing tube 14 inches long and 2 inches wide.
As you will see when you visit the websites, the cylinders you see in the picture are made out of aluminum foil, the coil and link for the coax are covered in electrical tape made out of #22 wire to hold them in place after adjustment, and the antenna was put on a broomstick about 3 feet above the floor in my basement shack/laundry room. This is about 3 feet below ground level. The measurements to start with and full description with pictures are all on the w0kph web page. I then proceeded to trim the coil back about half a turn from the original 15 turns, and adjusted the link (where the coax connects) to where I started to hear signals on my TS-120. Then, testing with power applied, I got a 2 to 1 match, and then with more, down to 1.3 to 1. WOW I thought, it takes power. And, the signals I can hear were about an S unit to 1 1/2 units below what the dipole outside was hearing. I thought, well, I am below ground level here. A little more adjustment and I got the match flat, and I was hearing W6XX in the San Francisco area with a signal just barely below that of the dipole. Now, one of the things noticed too was that the noise level present on the dipole of about S3 was practically non existent on the EH. Again, I was in the basement with the antenna less than 3 feet away from the clothes dryer and about 8 feet away from me and the radio, but the low noise level of this antenna is intrinsically low due to the way the E field (electric) and H fields (magnetic) are generated. And because the frequency range of the circuit is small, the EH Antenna harmonic radiation is all but nonexistent, but the bandwidth is wider than a conventional Hertz antenna. This from the www.eh-antenna.com website written by Ted Hart, but my experience would indicate that this is so.
So, I thought, here goes nothing. W6XX closed down his QSO and I gave him a call. HE CAME BACK to me and we proceed to exchange the usual signal reports, he gave me a 55-57 report while he was S7-8. I couldn't believe it. I was floored! (Or below the main floor in the basement) We had a 20-minute QSO, and discussed the antenna. He was skeptical as you would expect and probably you yourself are. I was too. Now, I still want to get the EH antenna outside and up in the air for further testing, but I believe it will perform as Ted Hart of the www.eh-antenna.com website and Jack, www.qsl.net/w0kph have had antenna's perform.
And, unbelievable, but folks have constructed a 160 meter antenna only about 6 to 8 feet tall that works incredibly, and the 10 meter version is 5 to 6 INCHES long, and 1 inch in diameter, made out of PVC pipe. That is the next one I will build to put up against the 10-meter vertical dipole. Check these out. They really do work. I will be putting up more information and details as I have time to work on them. If you get to try some of these for yourself, email W0KPH and myself and let us know how they work for you.
73’ KE0VH
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Small EH Antenna
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by KF9Z on August 19, 2002
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Folks, you don't get something for nothing. The law of physics can not be changed in order to make something look better than it is. The old saying 'If it's to good to be true...it is' and that is true in this case as well.
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Small EH Antenna
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by VE7NGR on August 19, 2002
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This same article was posted a few months ago on qrz.com. Lots of interesting discussion ensued - if the topic interests you, you may wish to look it up in the qrz.com archives.
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Small EH Antenna
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by N6AJR on August 19, 2002
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Mr. Kurt Sterba, who writes a column for WORLD RADIO magazine states in Septembers issue,pretty much that you can not change the laws of physics no matter how much tin foil you wrap on a toilet paper tube. His final comments are " lets see some actual field tests done on an antenna range against known antennas, ( dipole, 3 ele yagi, etc.) and see if the results are there. The theory is wrong and the antenna appears Not to work as claimed.Until then I will stick with conventional antenna. They do work."
Reminds me of the show on unsolved mysteries, where they had a certified psychic back up a expermental ghost hunter as to the effectivness of his new equipment. First , just who certifies psychic's and does it mean anything? and how does infrared heat detectors locate ghosts?? Its like pulling your self off the ground with your own boot straps.. Can't be done..ain't so. and I wasn't born yesterday.
By the way if you look up their website on the internet they will be glad to sell you one of these for a small amount of cash... hmmmmmmmmmmm
If it looks like poo-poo and smells like poo-poo, I don't have to taste it to make sure.. tom N6AJR
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Small EH Antenna
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by AG4DG on August 19, 2002
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I'll believe in the EH antenna when it eats into sales of Bugcatcher, Screwdriver, Hamstick, Hustler, Isotron, Isoloop, and other compact/mobile HF antennas. If it's such a great antenna, then why haven't the proponents produced test results and done presentations at IEEE conferences and other technical forums?
Remember the efficiency equation: efficiency=Rrad/(Rrad+Rg+Rc)
How does the EH antenna maximize radiation resistance and minimize ground and coil/conductive resistance?
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by W4WNT on August 19, 2002
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Before we all blow off this idea, remember that there are folks who live in CC&R areas that are looking for working small antennas. While they may never beat a triband beam at 100 feet, these things look like a great possibility for a back porch antenna lifted up with some suitable support. And they are simple enough to build yourself!
Meanwhile, I'm looking for a source for the variable capacitors that are used in these antennas.
73, Bill, W4WNT
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Small EH Antenna
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by W4CNG on August 19, 2002
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Smoke and Mirrors, Articles all, BUT in the world of communications nothing beats the full length dipole antenna as the standard of measurement on an antenna range. Let's go to the range where the truth is most often extracted (minus advertising hype). Let's also apply EIA RS329 the standard of measurement for gain against the reference dipole to the subject in hand. That should not be very difficult for such a small radiator of RF.
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RE: Small EH Antenna
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by WA4DOU on August 19, 2002
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For some strange reason, no amount of feedback, no matter how well reasoned and in harmony with the laws of physics and reality, can debunk this kind of stuff in the minds of those that long for, wish for and by golly are going to have their nothing antenna. Remember this, if it weren't for the simple phenomonon of "feedline radiation", these antennas would not perform at all. Buy some antenna books, read and study them and learn antenna theory. You'll be a lot better off.
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Small EH Antenna
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by W7KWS on August 19, 2002
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I haven't any idea if this antenna is gobbledygook or not. Many such panacea antennas are just that and nothing more. However, I always try to keep an open mind, inasmuch as a closed mind will reject all new scientific achievements.
Those that think that, just because an antenna isn't huge, that it can’t work should review the small tuned loop antennas used by the U.S. military. Amateur versions are written up in the ARRL Antenna Handbook and are very small yet exhibit nearly 100% efficiency when compared to a full size dipole. AEA made one and so does MFJ. They worked quite well.
In the meantime, the inventors of the E H antenna, Maurice C. Hately & Fathi M. Kabbary, or their employer (U.S. Patent No. 5,155,495), sure thought enough of this invention to spend some bucks on a patent attorney and filing fees.
I know that many patents aren’t worth the paper they’re written on. But at least reading this one will give you much more insight into this antenna than you probably have now. Take a look. It's on the WEB at the U.S. Patent and Trademark Office.
Maybe after some study, we’ll have some better, educated views of this work.
The URL is:
http://patft.uspto.gov/netahtml/srchnum.htm
73, Bob
W7KWS
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by AA5CH on August 20, 2002
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Recently, eHam.net provided a link to a website concerning an EH antenna for 160 meters...
http://www.qsl.net/iz7ath/web/02_brew/18_eh/index.htm
I'm not smart enough to know if someone is attempting to rewrite the laws of physics with this technology or not...it is an interesting read, nonetheless.
73,
Brad
AA5CH
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by WO5I on August 20, 2002
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Folks,
I am not a physicist or even an electrical engineer. But I am open-minded enough to NOT go disparaging the EH theory or design until I've tried it myself. I've seen several articles and web sites publishing results of experiments. Many of those results are favorable. For me to poo-poo it would be tantamount to me calling those hams, who I know nothing good or bad about, liars.
Consider:
Until Copernicus, the world thought the Earth was the center of the entire universe, and to openly state otherwise was a severe blaspheme,
Until Columbus, the earth was thought to be flat (good for propagation, BAD for sailing!),
Until Yager, the sound barrier was just that-- a barrier.
Until Armstrong, et al, few really thought that there'd ever be a man on the moon (and probably some of the naysayers still think that all took place on a Hollywood soundstage).
My challenge to the ham community that would write this idea off is this: build one yourself, per the directions on any of the published websites. They aren't expensive, they don't take any serious skill or expensive tools. The require a little patience to tune and fine-tune, but once it resonates, you can try it out head-to-head with any antenna you would otherwise use.
I intend to put my money where my mouth is and build one. I might find I've wasted my time, then I will take my "I-told-you-so's" like a man. But then again, there are those that think of ham radio in general as one big waste of time! After all, isn't ham radio chock-full of people that experiment? Maybe the EH is a better mousetrap.
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by W3DCG on August 20, 2002
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Well...
In 1980, didn't the idea of CPU speeds in the range of Gigahertz seem Far Out? If you would have told me then, that in 20 years, children will be burning their own CDs, not only I, but likely most of you would be saying, "...burning, as in, on fire- what? You mean riots, our children will be burning our cities?"
Or something similar.
I mean, my rig uses a PTO- how long has that been completely OUT.
How long ago did the first Trans-Oceanic flight occur?
When did the first human reach outer space?
I don't know the answers...
I heard rumors, that Nikolai Tesla had some very Far Out ideas, probably landing him into a lot of hot water, because if they worked, the power structure of civilization might have crumbled.
Sure, I'm a skeptic, and have been known by a handful of people to be intensely cynical from time to time.
Yeah... antenna theory then and now is basically still the same, based upon the Laws of Physics as they are currently known and taught.
Remember when Cell Phones were relatively gigantic, with the telescoping whips, ha! Remember when it was the big status symbol, and now, they are common-place. I know a few people who HAVE NO LANDLINE, but they have a cell phone.
Now if you want it bad enough, you can surf via some cell phones.
Recall when surfing was all about beaches, waves, and hydrodynamic low-drag boards. The scent of coconut suntan oil...
Place the latest Notebook (remember when they were called Lap Tops, now they are called NOTE BOOKS), set the latest Notebook next to a TRS 80, Commadore 64, PETs, audio cassette tape drives...what ever happened to ZIP drives, was that a FLASH IN THE PAN or what? Rendered completely useless by ever faster, higher capacity hard-drives, and now we're at Read/Write CD drives.
I am skeptical, but willing to admit, that new discoveries are probable, and that science/research is in bed with industry- and so the struggle for power is the same as it ever was.
I for one would be very sad to see towers and the precise, gorgeous, metalic structures that adorn them become obsolete before I ever get the chance to have one such sculpture myself.
I'm keeping an Open Mind- it's all I can do in my ignorance. I would imagine, that the developers of such a "crazy" far out paradigm, may very well have a fairly in depth understanding and grasp- of currently known and widely accepted, field-proven antenna design theory.
And it so happens, that I derive some small amount of twisted pleasure, when what should not work, performs in ways that defy conventionally accepted theory. It just tickles me pink.
Wouldn't it be great for the notion of Super Gain to be true, for the Hex Beam to actually work even if most hams don't completely understand precisely why, and for more research on all of that to be conducted.
Wouldn't it be great for the Carolina Windom to actually work as well as the makers claim- for the espoused modeled radiation patterns to actually be- a fairly accurate proximity of their true performance. For me it would, since an OCF dipole is all I have! ha.
I am aware that it seems, most antenna advancements work within the realms of conventionally accepted scientifically proven theory. Motor driven variable length elements, yielding wide range continuous optimized multiband coverage- one 3 element Yagi-Uda can practically do the job of at least 3, 3 element mono-banders. That is very cool. What next, remote controlled variable boom length? It would be virtually impossible to argue that in theory it does not work as claimed. Literally revolutionary, (motors inside each element turning). And at the same time NOT- (Only having to rotate the array a maximum of 180 degrees for 360 degree coverage is at best, non revolutionary). That is BEYOND cool, and simply- awsome.
It is often human nature to be skeptical, even zealously critical, of new and crazy- preposterous ideas.
It means having to learn more and for some people like me, it will take years to attain a solid grasp of current complex antenna theory- and then along comes some new fangled completely different yet apparently true theory- back to square one- and those that make these discoveries likely will be not so generous in the sharing of any such knowledge. After all they will have earned it the hardest way, having endured the pressure of nay saying antenna theory parias and skeptics at every turn... and it has to be tough, having formulated theory and devised the tests to prove or disprove the theory- what if they theory is proven wrong? If proven right? There'll be much profit to gain with such knowledge.
Human nature will never stop delving, never stop trying to improve upon that which is already the ultimate. Some people are compelled to keep dreaming, and the quest for a better mouse trap will never end...and I'll bet, that when someone has created the most perfect mouse trap beyong compare, it will be a matter of time before it is once again, improved- beyond compare.
Speaking of Surfing, how about that "new" Cheryl Crow video. I'm talking about that VW Van, and the pretty waterfall... and the *acoustic* guitar, and the *lyrics* are okay, too ;)
Cheers.
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by AB7RG on August 20, 2002
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WO5I hit the nail on the head... While I too am very skeptical of this antenna design I won't rule it out until I've tried it. (For those moaning about there being a link to sell these antennas on their sites, does this antenna look that hard to build???) It might be a fun project and would make for a great traveling antenna. It certainly wouldn't be hard or expensive to build! Anyway, as Amateur Radio operators we MUST try to experiment and be able to look at different (and sometimes radical) new ideas, even on old tried and proven concepts. And what if this antenna design does help out those in CC&R neighborhoods, even if it doesn't work like a yagi? Hey we need those guys on the air too!
I think that in the interest of furthering the radio art and for scientific experimentation that we should not ever discount something before we try it. After all, what if Marconi had listened to the scientists and so-called experts of his day? After all, radio was "useless" and would be line of sight, at best. Marconi dared to dream and was brave enough to experiment. I hope that as Amateur Radio operators that we can continue to have an open mind towards experimentation and be able to continue to further the radio art.
73 Clinton AB7RG
"The important thing is not to stop questioning." -- Albert Einstein
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by KE4SKY on August 20, 2002
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I sure hope that Osama Bin Laden and Sadam Hussein's armies use this antenna...
This sounds like the Smoketron to me!
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RE: Small EH Antenna
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by KE0VH on August 20, 2002
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I did post this same article at QRZ.com a couple of months ago, and first of all it took Eham forever to put it up. The reason I wrote it was to help out fellow hams who might not know about a smaller design that will help in maybe a situation where someone can't put up a full size beam, or dipole, and and have a kilowatt like a lot of people who gripe when someone comes up with a new idea. Frankly, I am really irritated that so many come on and "diss" an idea without even having tried it. I am an RF/radio engineer with years of experience building antenna's and wouldn't put up something that was bogus. I am NOT trying to SELL anything, just SHARE AN IDEA. Those of you who are critical probably haven't even tried it. The Antenna DOES work. If a corporation or company has the money to design and produce a smaller antenna that does, like MFJ and the like, GREAT! If not, how about just sharing ideas that work without having to have a high and mighty opinion without having tried it. Check your attitude people.
Lets respect others viewpoints and WORK folks, and unless you have tried it frankly I think you should keep your critical views to yourself. Try it and put some work into and then present your results. I did. Otherwise, let those of us who are willing to experiment a little bit, build and try things and try to help others do so without the "benefit" of your not even experienced opinions. Try it, disprove it, and then present your findings. Then you will gain respect for at least having tried.
KE0VH
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by KA1OGM on August 20, 2002
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In case no-one noticed, the initial post on this topic contains clear and explicit performance claims of 1 to 1-1/2 S-units down, in comparison to his full sized antenna. This is the same general performance that I've experienced with the design shown in the picture, over the past year and a half. The controversy of the past ten years surrounding the CFA and EH antennas are founded upon claims that they perform as well as, or better than full sized antennas.
We are dealing with a design here that can be used for restricted space situations with the expected reduced performance. Nobody has come onto this thread making any wild claims that defy the laws of physics, or the basic math for antenna design that was worked out a century ago. That Kabbary of "CFA" and Ted Hart of "EH" have been working on commercial applications all this time really has very little to do with the application of this compact, reduced performance alternative for ham radio applications.
This is a ground level vertical design that can be experimented with to achieve low angles of radiation. The longer the cylinders are, the lower the angle of radiation (to a point). Even lower angles of radiation can be achieved by using plates that are shaped like inverted cones, or a cone-disk arrangement, all of which is described in detail for practical construction on Jack Arnold's website at:
http://www.qsl.net/w0kph/
The "catch" with these antennas is that with lower angles of radiation, some claims might ring true about performance exceeding that of a single element full sized antenna, but most hams will find performance running down by 1 to 2 S-units in comparison to any full sized antennas they have at the same location. In many experiments I've done, however, I've gotten "hot" angles on the short, fat dipoles that produce better Rx and Tx performance working DX stations out at that favorable distance for the angle. This is a VERY interesting antenna design in this respect, and it bears scrutiny and investigation by those who would actually experiment with them.
And yes, there ARE some perplexing phenomena that can be produced when using these antennas. They are intriguing, and lead me to suspect that there are things going on with these designs that have yet to be adequately explained. Of course, if you never experiment with these things to any significant degree, you'll never get to that head scratching point, and you'll never have a chance to find out what I'm referring to.
Jeff Barnard
KA1OGM
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by N3HKN on August 20, 2002
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First, the insulting and ill-tempered remarks above are disgusting. Why are such people so angry that they must sit around and await any opportunity to lash out with blind criticisim. I hope that these poor representitives of the Ham community are in a very small minority.
I have not built one of these antennas but I do have restrictions and have read the info on the associated web sites. Now that someone has "independently" constructed one I will try it. What harm can it do? Perhaps that is the question the above "personalities" should ponder as they sit in their dark little rooms doing whatever people like that do in private.
I will take a shot at the 20 meter version and see how it compares to my Gap Challenger vertical dipole. This is a fair comparison due to efficiency and angle of radiation. By the way, GAP has a similar multiband unit for over $400 for sale. I have yet to hear about any real-world results on this unit. It uses a flat plate with a metal box about a foot above it supported on an insulator. From articles in Antenna-X the tuning unit is the critical element.
Dick N3HKN
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by KG6AMW on August 20, 2002
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Dick, I've seen some off color comments, but they don't seem ill tempered. Its the way a discussion goes. Some believe it, some don't, and some want more evidence. Until you obtain data in a controlled environment and put it into a report, all we have are just comments. Merrill
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by W2BRI on August 20, 2002
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Being very interested in all types of antennas I went out and built an EH antenna. Darn thing was so small and cute. I put it outside and compared it to my triband yagi...probably not a fair comparison. The EH while attractive and fun, did not seem to hear very well. Yeah, I got a good match, and my family made all sorts of funny remarks about my magic wand, but it worked horribly. I don't mean bad, I mean horribly. Maybe I did something wrong --as some might like to point out. And maybe I did. But it took me about 5 minutes to realize, my EH didn't work a darn. Now if someone is interested in small antennas that really work, I would strongly suggest building a magnetic loop antenna. My 80 meter 12x12 2 inch thick mag loop works great! and for the size you can't beat it on 80. Sure, you could build a smaller one if you want. I highly recommend this antenna and you don't have to re-write physics in the process. Please email me if you would like more info.
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by WA4DOU on August 20, 2002
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Flat earth? Closed minds? Unreceptive to new ideas? Since when did inefficient antennas become a new idea, warrenting much experimentation?
In free space, a theoretical point source of electromagnetic radiation is called an isotropic antenna. It is the point of reference we use to understand the 1/4 wavelength and 1/2 wavelength antennas, also in free space. The quarterwave displays a "gain" of about 1 db over this isotropic reference and the halfwave displays a "gain" of about 2.14 db. These can be turned around to state that an isotropic antenna has negative gain of 2.14 db over a half-wave antenna and negative 1 db over a quarterwave. Bring both of these antennas into close proximity to the earth and you have gain over them in free space, because of ground reflections. These are the real world reference standards by which we understand more complex antennas. 1 to 1-1/2 S unit down equates to about 50-90 % power loss. Why would you generate expensive r.f. energy and then be content to throw away 50-90% of it? Wouldn't it be better to generate less of it and radiate it more efficiently?
I have lived in many places as an adult and I have experimented with many antennas. A common thread thru it all is that when you seriously shorten an antenna, you seriously diminish its performance. I have lived in beehives, townhouses, duplexes, mobile homes, single family dwellings, with and without antenna restrictions. I have used my share of clandestine antennas and I have never seen a circumstance where I couldn't erect outside antennas. All it takes is imagination and willpower. Any are to be preferred over any of these newfangled miracle antennas that promise much and deliver much less. Do what you please. I'll continue to use real antennas that deliver real performance.
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by WO5I on August 20, 2002
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It's OK, Roy. Nobody, least of all ME, is asking you to take your proven antenna to the dump in favor of something untried or inferior.
My point, and that of several others on this thread so far, is to say "why not?" to the idea of EH. I'm not encumbered by a vast knowledge of antenna theory which prevents me from hoping that something like this would work. I read the article in World Radio, and all the negative comments regarding the antenna, and am unarmed to argue any of the theoritical points. The EH could very well end up being the "cold fusion" of antennas.
However, I've also read some good comments and favorable test results and think that the EH antenna is worth a weekend's worth of my time to tinker with. Even if the thing won't radiate beyond my back yard, I'll get to sharpen some rusty skills at forming aluminum foil, winding coils of wire, cutting PVC pipe or cardboard tube -- skills that will undoubtedly bail me out of some unforeseen jam like McGyver with a magnifying glass.
This argument, or friendly ham-like discussion, is akin to arguing the merits of of QRO vs. QRP. Nobody will dispute that the 1.5KW and stacked monobanders will be heard much clearer through a pile up than an FT-817 and telescoping whip, but try stuffing your Alpha amp and tower into your backpack!
I, too, have found somewhat clever ways to radiate in adverse housing conditions. My current solution is to thumb my nose at the CC&R and ground-mount a very low-footprint multi-band vertical, hoping any neighbors that might care about such things will assume it's a deep sea fishing pole (actually had one neighbor THINK THAT! HI HI).
The EH is just another option in the realm of possibility. Let beauty be in the eye of the beholder.
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by KE4MOB on August 20, 2002
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I think it's important to realize you can work QRP using only an ordinary lightbulb as an antenna. And people regularly load up metal guttering with fair results. Sometimes they can work stations using dummy loads for antennas.
We would like to think antennas are wonderfully complex instruments...fact is, you can radiate a workable signal with darn near anything.
This antenna is probably a perfect example.
They used to have a lot of info at www.antennex.com...I thought the so-called "tests" in Egypt were a failure?
Steve, KE4MOB
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by KD3V on August 20, 2002
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!!! LISTEN UP SKEPTICS !!!
Please stop making fools of yourselves! If you haven't tried it you have NO BASIS for saying anything!
We made one! I used it! it works!
I am an electrical engineer. I have been one since 1982.
These EH antennas in fact:
1. ... are not "getting something for nothing",
2. they are not "changing the laws of physics in order to make something better than it is",
3. they agree completely with the law of physics that tells us how to get radiation, and for those that have taken the time to read the relevant website, this is called the "Poynting Theorem". This antenna is simple a DIFFERENT method to work this "law of physics".
4. They WORK! I know because I used one!
I sent the article to a friend who wanted to make one, he had a friend of his duplicate the 20 meter version that was detailed on the web site. He used it and then I put it up in place on the roof.
Simply put, I worked the world on it! I live in Hollywood Calif.
From John in South Africa, a 5-7 ... on the LONG path... a FM5 in Martinique, VK's ZL's ZK1, you name it and I only had it for 3 days!
So! Read the web sites! These antennas are not using feedline rariation, they are genuine rariators using a different method to create the crossed EM field and as a result they do not need the "linear" distance used by a diplole!
These antennas just do it DIFFERENTLY!
Yea, i get upset by the "ignorant" who speak up with no basis from which to do so. In the place of facts you put baseless opinion, and in the place of knowledge you put "authority". You are all only making fools of yourselves and those of us who take the time to "find out for ourselves" are the ones who gain real knowledge!
We were curious so we built one and we found that it works! Simple. We didn't know until we tried... but we also didn't try to slam it until we KNEW something about which we wanted to speak!
I would have posted a few photos but you can already see them when you go read the web site referenced! Ours looked just like theirs do. We used copper plate wrapped around PVC cylinder. Total length.. just like on the website! http://www.qsl.net/w0kph/
This is the link that describes the "full network" verion that our friend built.
http://www.qsl.net/w0kph/fullnet.html
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RE: Small EH Antenna
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by KE4MOB on August 20, 2002
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How do you generate an E field without generating an H field?
Could somebody explain this to me?
Steve, KE4MOB
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RE: Small EH Antenna
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by KE4MOB on August 20, 2002
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How do you generate an E field without generating an H field?
Could somebody explain this to me?
Steve, KE4MOB
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Small EH Antenna
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by KA1OGM on August 20, 2002
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This subject is always one that elicits contentious debate regarding claims made by commercial interests. It also brings out a fair number of those who are not only knowledgable and technically savvy who have investigated one or more of these designs, but also those who have blindly stumbled onto them and been quite excited about what they ended up with.
Anyone who is serious about efficient antennas will have issues with the two cylinder plus coil design, however, because it really isn't a very good antenna. But compared to NO antenna this is one of the more intriguing designs around because it's small enough to be used indoors.
I, for one, cannot operate a 75m loop in my basement and make contact with anyone, near or far. I can, however, operate a two cylinder plus coil antenna for 75m in my basement and maintain contact with everyone I've tried this with, when first making contact with my outdoor inverted Vee (and vice-versa). I even got a qsl e-mail from an SWL 500 miles away who heard me making a test one night on 75m AM. Admittedly, my effective radiated power is a tenth of what it was on the outside antenna, but I have to say that if I was restricted to an apartment, this would be my antenna.
Like I pointed out in my last post, nobody's making any wild claims about this design, and nobody will ever dispute that a monoband directive array is better. What's nice about this design is you can make it sloppily and still get on the air, where otherwise you might not be able to get on the air at all.
Jeff Barnard
KA1OGM
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Small EH Antenna
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by W3JJH on August 20, 2002
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I'm open-minded, but not so open-minded that my brain has fallen out.
1. My dummy load has a 1.1:1 SWR on 20-m. It doesn't radiate very well.
2. At 6 dB/S-unit, a drop of 1-1/2 S-units represents a 90-% power loss. If the signals coming in the side of my dipole were only 9 dB above those from a small "EH" antenna, I would start checking for loose or corroded connections on the dipole.
The current in a wire in an H-field is proportional to the strength of field times the length of the wire. Use a shorter wire, get a smaller signal. The potential on a conductive surface in an E-field is proportional to the strength of the field times the size of the surface. Use a smaller area, get a smaller signal.
Scotty is right: "Ye canna change the laws of physics!."
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RE: Small EH Antenna
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by W7KWS on August 20, 2002
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In using wire length as a linear indicator of signal capture/radiation efficiency (presumed law of physics in previous post), how do you account for the fact that a tuned magnetic loop antenna, at 8.5 Ft. in circumference, is only down 1.0 dB below a "large antenna" for the same band? Reference the ARRL Antenna Handbook, 16th edition, page 5-13, loop design No. 5.
Good wishes to all in hopes we all learn here.
73,
Bob, W7KWS
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RE: Small EH Antenna
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by W7KWS on August 20, 2002
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I forgot, the band of reference in my last post is for 20 meters (14.2 MHz.).
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RE: Small EH Antenna
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by K3AN on August 21, 2002
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I am on the verge of achieving a radical breakthrough that will finally achieve the dream of almost limitless free power from plain old water! Since water consists of just hydrogen and oxygen, combining those elements to release the power results in no pollution. I will be prepared to demonstrate this publicly in the near future. To the invitees of that demonstration, I must ask in advance that they pay no attention to the man behind the curtain ;-)
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RE: Small EH Antenna
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by W3JJH on August 21, 2002
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I don't have a copy of the reference which W3KWS cites, but please allow me to make some further comments. The "mechanics" of wave propagation are well known and have been rigorously descirbed for about 150 years now. Most electrical engineering students take a course in Fields & Waves during their junior or senior year. In that course they learn that small radiators approximate a point source; such antennas have omnidirectional patterns and radiate equally poorly in all directions. Large radiators are more efficient, but are also more directive. For example, a half-wave dipole works well to the sides, but is deaf and dumb off the ends. Extremely large radiators generally do not work well because of phasing problems with the signals coming from different points on the antenna.
Note that a small antenna that has an efficiency many dB lower than a dipole may hear a signal coming from a bearing off the end of the dipole better than the larger antenna.
As an analogy, consider a set of loudspeakers. It is possible to construct two different loudspeakers systems which have the same low frequency cutoff using different size drivers and enclosures. Let's say we want a 20-Hz low end cutoff, and we build one system with a 38-cm (15-in) driver in a 600-l (21 cu ft) enclosure. The system efficiency will be roughly 1 %. If we build the other system with a 11-cm (4-1/2-in) driver in a 30-l (1.1 cu ft) box, the system efficiency will be around 0.05 %. At low frequencies we'll be able to get the same sound level out of the second system only if we use 20X the amplifier power. However, the smaller system will do a better job of reproducing signals above 1-kHz; the bigger woofer becomes an extremely large radiator at these frequencies. This is why a proper audio system has a woofer and a tweeter (at least!).
Similarly, we shouldn't use a 2-m ground plane on 80-m or an 80-m vertical on 2-m.
HF antenna testing requires large, open spaces and calibrated test gear which most of us do not possess. Even some manufacturers of HF antennas do not have a proper antenna test range. I take all antenna performance claims with a grain of salt until I have verified that test data actually exists and was properly measured.
I live on a small city lot. I can just fit a 70-ft dipole with loading inductors on my site. Fed with ladder line, it works sorta OK on all the bands from 160 through 10. I also have an Outbacker on an Alpha-Delta stand. In some cases (depending on the bearing to the other station or signal vertical arrival angle) it works better than the dipole. But, except on the 12- and 10-m bands, it is a less efficent radiator than the dipole.
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RE: Small EH Antenna
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by W7KWS on August 21, 2002
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William (W3JJH),
The problem that I see with your ideas about size of an antenna relating to its efficiency is that, while size is a factor, it is not the only factor involved. Your comparison of an isotropic source to a dipole suggests that a dipole radiates more energy than the point source. The fact is that it does not. Except for heat conversion in the resistance of both antennas and assuming for the moment that there are equal or no feed line losses, both antennas radiate exactly the same amount of energy, regardless of size. The differences you describe are due to the directional nature of the dipole versus the fact that the isotropic antenna distributes its energy equally in all directions, therefore, no one direction benefits over another, as is the case with the dipole.
Regarding wire length versus antenna efficiency, I quote from my copy of the 5th edition of the Reference Data for Radio Engineers, page 25-7; “In addition, antenna efficiencies vary from about 70 percent for a 0.15-wavelength physical height to over 95 percent for a 0.6 wavelength height. This is for a vertical, and doesn’t account for why a loop can be above 90 percent, but it does show that a very short antenna of 0.15 wavelength can still radiate with more efficiency than one would suspect from a linear formula such as you proposed in your previous post.
Make no mistake, I doubt that the EH Antenna works very well, but I know that the tuned loop does. And, it is a small antenna. In facts, it can be a small fraction of a wavelength and approach the efficiency of a dipole. This is because factors other than size are involved. If you can get a copy of any ARRL Antenna book and read about it, you will see that it is true.
Also, you no longer need an extensive antenna range to determine the value of an antenna. There are many very good computer modeling programs that produce results that are very close to what you would find on an antenna range.
Believe it or not, we only think we have a handle on physics. People are proving every day that even Einstein didn’t have it all right. THERE ARE NEW THINGS TO DISCOVER ALL THE TIME. Even the fact that a small antenna like the tuned loop can work very well compared with much larger antennas.
Whether the EH Antenna is a good one is a simple matter of analysis. I wish I had those analytical skills myself, but I don’t, so I rely on the published references of those that do have the skills. The loop has been studied for years and has been proven to work.
Maybe we can attract someone to this discussion that can do a computer model of the EH antenna and give us some real data that we can rely on.
73,
Bob
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Small EH Antenna
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by N2HBX on August 21, 2002
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C'mon, guys. Let's not lose sight of the fact that this is a HOBBY, one that fortunately lends itself to all sorts of experimentation. What works for someone might not work for another, but if it doesn't, instead of just pooh-poohing it, try to se if you CAN make it work!
I knew a gentleman by the name of Jim Waldron. His callsign escapes me at the moment, and I'm sure he is an SK by now. He founded a company called Com-Rad Industries. He had designed and manufactured shortened antennas similar to the EH design. In fact, he designed and sold similar antennas from 160 meters up to 450. Of course we had our local "experts" that said it didn't work and all his so-called "testimonials" that he had were all hired shills to talk up his units. But I sat in his shack for about two hours and tried them myself, and the results were satisfying. I never bought one (or built one) myself, but I thought they were kind of cool and seemed to work. His company was the progenitor of a company now known as Untenna (www.untenna.com). Apparently somebody thought the idea had merit, even though the current company specializes in commercial two-way antennas and has left the ham market.
Point is, don't get caught up in the physics of it all. If the laws of physics applied to everything literally, bumblebees couldn't fly.
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Small EH Antenna
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by K9FE on August 21, 2002
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OK, I built one for 20m. (well two)Took about 2 hours including rounding up the materials and getting it tuned to 14.200. It works! No it isn't going to put Force 12 out of business, but I have limitations on where and what I can put up. I was so floored that I brought it to a club meeting to show it off.
Our club has a lot of techies but we never knock an idea until we can prove it wrong. A few members got excited and built them and they all worked. In our club we have EH antennas from 10m to 160m. AH6EZ Dick, is the big EH experimenter in our club and an engineer for Motorola who worked 47 states on 160 in one contest last year on an EH. His 160 is on the EH page of W0KPH. 10 feet tall and 16 inches in diameter and can handle over 600 watts! It works when it is 10 to 15 feet off the ground and suspended from a tree.
Until you walk in a mans shoes do not call him a liar. Build this thing and build it right and it does work. Sure it defies any old antenna theory so if you do not believe it build it "correctly" and prove it does not work, I doubted it, but now I have 3, two for 20m and one for 40m. The 40m is only 24 inches tall but works better than my mobile 40m antenna...so I am going to mount it on the back of the car and use it...has better bandwidth than my center loaded mast.
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RE: Small EH Antenna
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by N2KPE on August 21, 2002
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WO5I: I would very much like to be kept posted on your results. Do you have any idea which band you will try/ I would especially be interested in 40. Tnx and 73.
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RE: Small EH Antenna
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by N0TONE on August 22, 2002
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The website mentioned early on was by an Italian ham who built an EH for 160 meters. He gave "results" with QSOs listed that seemed favorable. But, he obviously knew that did not provide particularly useful data - one need to compare with a "known" antenna. So he built a 160 meter vertical to compare it to. His 160 meter vertical was severely compromised, being all of 30 feet high, with only four too-short ground-mounted radials. A configuration which normally provides an antenna of maybe 5-10% efficiency. He then made lots of QSOs on both the EH and the poor vertical. In all cases, the vertical outperformed the EH by about 5-10dB.
In his case, he either did not build the EH properly, or he demonstrated that EH performance is not superior. He remains open to either conclusion.
There are some global points to be considered here:
1) Who cares if EH is operating with new theory? What we REALLY want to know is if this small antenna can do better than other small antenna designs.
2) Therefore, to satify #1, we need to see some genuine field strength tests made on EH antennas versus other small antennas, which are designed correctly. According to the Italian website referenced above, the 160 meter EH seems to be operating at about 0.5% efficiency. I have a 12 foot long mobile 160 meter antenna that does better than that!
3) NONE of the websites describing the EH antenna gives adequate information for measuring its performance. They make claims about the antenna's impedance, but do not tell you how to go about making those impedance measurements. I asked Ted Hart once how to make those impedance measurements and he said "measure the input impedance, then use math to calculate what the impedance is on the other side of the phasing network." But - he says the phasing network cannot be treated as a matching network, it requires new math. So, no go.
I have built many small antennas over the years. By keeping the conductors big and fat where currents are high, and by using only low-loss dielectrics where the voltages are high, a small antenna can be made efficient. It won't be broadband, and it won't be 50 ohms. So the key with small antennas is not only proper construction, but then using good parts to effect the Z-match.
Inductors in your matching network need to have large surface areas. #8 gauge or larger wire, or better yet, 1/4" copper tubing wound into inductors can be low loss. You have to trade off available space with desired Q.
Capacitors are sometimes harder. There are no good low-loss dielectrics conveniently available. Coaxial cable makes a lossy capacitor. Window glass makes a poor dielectric. PVC and similar home construction materials have high losses when used as a capacitor dielectric. The best I've been able to do is make capacitors out of concentric copper pipes. I use PVC as a spacer, but try to minimize the number of those lossy spacers.
I have a center-fed vertical for 80 meters, which is six feet high (that makes it fit my attic). My measurements show its efficiency to be about 25%. Most of the loss is in the matching network. That puts it 6dB down from a full-sized 80 meter vertical. Yes, I work DX on it, rather a lot of DX in fact. Bandwidth is only about 25kHz at the 2:1 points. If I drive it with 1.5kW, solid carrier, the antenna itself does not get warm at all, but the matching network does, mainly the inductor. So I know what part of my network could stand the most improvement.
Use common sense. Don't worry about whether it's an EH or just a shortened center-fed vertical. Build the antenna, tune it as described, then do the "power" test. If you're on 160 or 80 meters, wait until daytime when the atmospheric absorption is so high that nobody can make a QSO. Lock your key for a few minutes, then shut down. Go feel the antenna to see what's warm, and work on reducing loss in that area. For 40 meters, about the only thing you can do like this is wait until nighttime when all the SW BC rolls in, and park your carrier zero-beat with a SW station, and do this same test. For 20, 15, and 10, there are lots of times when the band's dead.
To the guy who said "In the meantime, the inventors of the E H antenna, Maurice C. Hately & Fathi M. Kabbary, or their employer (U.S. Patent No. 5,155,495), sure thought enough of this invention to spend some bucks on a patent attorney and filing fees. ", well, don't get too worked up. Filing patents is easy - there are books you can get that show you how to self-patent. Under $100 is the most you need to pay, unless you happen to like paying greedy corporate attorneys, or patent searchers. Yes, I'm such a person - willing to take big bucks to do things you can do yourself!
Have fun guys, building antennas has more challenge and thrill than any other part of the technical side of the hobby.
AM
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RE: Small EH Antenna
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by W3JJH on August 22, 2002
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Bob:
You're correct that the relationship between the length of a conductor and its efficency as an antenna is not linear. However, for systems which are small compared to a wavelength, a linear relationship holds. Loop antenna work by having multiple turns of wire in the field. The potential across the terminals of a loop which is small compared to a wavelength is
E = k*f*N*S*B,
where k is a fudge factor depending on the core material (if any), f is the signal frequency, N is the number of turns, S is the cross sectional area of the loop, and B is the field strength. More turns will give a stronger signal. So will a larger loop.
As the dimensions a radiator begin to exceed roughly 0.1 wavelength, its radiation impedance is defined by a rather inconvenient relationship with its geometry.
As the size of the radiator becomes small, the impedance of the antenna becomes a poor match to the impedance of free space. As the size approaches zero, the SWR at the interface between the antenna and the medium becomes infinite, and no power can be radiated. The impedance at the input to the antenna may give a perfect match to the transmitter, but, if that is so, all the power will be burned in the antenna.
None of this means that one can't communicate using small antennas. I've done it. I use a compact antenna with my backpacking QRP rig, working all over the world with an FT-817 and an Outbacker. But, even when I'm camping, I'll put up as much wire as I can when I have the time and space.
73 de W3JJH (John, I go by my middle name)
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RE: Small EH Antenna
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by W7KWS on August 22, 2002
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John,
Nice bit of information. I've built several tuned loops for 30 through 10 meters and they've worked very well. I've never done any analysis on them, but I've taken stock in the numbers published in the more credible references and they've compared to dipoles favorably.
I don’t know how this squares with your thoughts, but I don’t use multiple loops, just a single turn with a high voltage capacitor at the bottom of the loop, as shown in the Antenna Handbook. This capacitor needs to be high voltage as the high Q and the power levels make for a very high voltage at this location. The loop is around two and a half feet in diameter and is made of 1” copper water pipe, soldered at all joints. This loop is very low impedance and the handbook shows a stub kind of feed. I took an idea from MFJ’s loop and feed a small exciter loop (about 10” Diameter) instead of using the stub approach. This small loop is situated inside the larger loop and in the same plane. This makes the feed VERY easy. I make my own split stator capacitors as per the post by Notone, but I use Teflon tubing for a dielectric for lower losses and a higher stand off voltage. Teflon is about 1000 volts per mil. of thickness, if my memory serves me correctly. This arrangement takes a KW +++ with out any perceived heat build up and tunes 14 MHz to 30 MHz. very nicely.
Thanks for the input, it is appreciated.
73,
Bob
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by KD7PKO on August 22, 2002
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GE
Just a couple of thoughts come to mind for me about this antenna:
1)Ham radio is about experimenting right? So if I can experiment with something that will only set me back five bucks, I'm all for it! It kills me to consider my $800.00 radio works best on ten bucks worth of wire and some ceramic insulators hi. hi. So why not try it on free tin foil and cardboard? I hate instant karma......
2) To those who blow off "new ideas" keep this thought in mind: "Why do people with closed minds always have an open mouth?" I saw this on a bumper sticker and will always remember it?!?!?
BTW, whenever I have more than a couple of thoughts in mind, I always get a headache! Must be my limited mind. Naw, it's the chronic RF exposure!!!
73 and happy tinkering!
Chris-KD7PKO
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by K3PZ on August 23, 2002
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This topic was recently discussed on QRZ.com and drew alot of the same scepticism, controversy and nasty comments no doubt by the same people as here. The human ego can be a very vengeful creature. Having "a mind that is open to everything but attached to nothing" is what has allowed man to become the superior beings that we are today.
Paul Zora
K3PZ
Myrtle Beach
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RE: Small EH Antenna
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by WB2WIK on August 23, 2002
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I haven't built one.
KD3V says he has, and is in Hollywood, which is close to me. So, I think the path of least resistance would be for KD3V to bring his EH antenna to my house, where we can try it, empirically, against other antennas, and accurately measure the results. KD3V, are you up for this?
Then, he and I live close enough that when working almost anywhere, we'd be the same distance to the test station; so, we could each be "home" and run virtually the same experiment.
Antenna efficiency has very little to do with performance. All power delivered to an antenna must be either radiated, reflected or converted to heat, light, sound or motion. Since I don't have any antennas that convert energy to light, sound or motion, I'll bet it's radiated, reflected, or converted to heat in virtually every antenna there is. If the power is all radiated, it's a 100% efficient antenna. I can get a paper clip to do that, with a small matching network.
The initial RFI problems discussed in the article are likely more the result of poor antenna placement than anything else. Of course low antennas placed close to the home will couple to more appliances prone to reception of interference than nice high, elevated ones will. Such is the inevitable drawback of most "stealth" installations -- you may not see them, but they'll find your electronic appliances, and often times, those of the neighbors, as well.
I'm up for the "EH comparison," any time. Let's set it up.
WB2WIK/6
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RE: Small EH Antenna
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by N0TONE on August 23, 2002
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When comparing two antennas, keep things as close to the same as you can.
In brass terms, don't compare the EH against a dipole. The EH, as proposed, exhibits properties of a vertical radiator. EG, if you can keep the losses down, you will generate more low angle radiation than a horizontal antenna.
So, please do not compare against a Yagi - they are different animals.
The original posting included clues to this effect. It claims the antenna is close to 100% efficient, but then confesses that its performance is fully 1 to 2 S-units down, which places it a lot closer to 10%, than 100%. But that's assuming the radiation angles are the same between his dipole and the EH, which they're probably not.
So far, the comparisons people have made between the EH and other vertical radiators support a contention that the EH is merely a small, compromise antenna, with some thought given to reducing the losses. It could do a lot worse, but it IS a compromise antenna.
Anybody who's put thought into how to minimize losses in a short dipole has built antennas with fat radiators like the EH. I have several myself.
My thought - copy it, but don't try to explain its operation on a "new" principal. The actual behavior of the antennas as others have describe them are perfectly in accordance with predictions from any of the modelling software packages that claim to model "ordinary" antennas.
This is a well-thought out small antenna, not a new concept.
AM
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by OK1FOU on August 24, 2002
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Hi folks,
I have always had "antenna placement problem", so CFA and EH was an interesting option to experiment with.
I tried to build a CFA, with the kind suppoort of W0KPH. Unfortunately, I was unable to tune it properly. It was possible to hear something on it, but transmission was basically impossible. When I looked closer into the "matching network", I was sure it could be matched to 1:1 SWR, but only as a result of perfect match to the matching network's own loss impedance. When perfect 1:1 match occurred, all signals from the band disappeared. The nmatching network was one of the recommended ones. This kind'a device reminds me of perpetuum mobile.
Later I tried a EH. I think that this one, being a quite open resonating circuit, might actually radiate some power, but I was not successful to tune mine into the band. It was far too sensitive to anything in the surrounding environment. At least it does not work in limited space.
I can understand that EH might need something like 0.75-1.5 lambda free space around it. Or maybe, to the contrary, it works fine as a resonant driver if a metallic structure is nearby.
My practical test & my 2 cents.
73 Jindra OK1FOU, OM9AMU
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by VK4JAM on August 24, 2002
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The antenna design presented here and on referenced web pages is an interesting design. I do not doubt that it works well. I plan to build one (perhaps with some modification to the matching network). I believe this antenna design is a good compromise for mobile / portable / restricted space applications.
Not so sure that I see this as a new design. I see it as a “short fat” dipole, with an interesting matching network. Taking this approach and using NEC or similar computer analysis tools it can be seen that the antenna would produce a gain of around 1.76 dBi. A little down on a normal dipole but not too bad for it’s size. This calculated result does agree with the observations reported by various people who have built the antenna.
The theory for the short dipole antenna is presented in many text books.
One which I recommend is:
Kraus, John D.: “Electromagnetics, Third Edition,” McGraw-Hill Book Company, New York, 1984.
Pages 620-633 give a good explanation of the Short Dipole.
An interesting design … Yes
A new discovery … I don’t think so.
73’s
Andrew
VK4JAM
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RE: Small EH Antenna
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by W7KWS on August 24, 2002
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Andrew,
Is there any chance you would be able to share further results from your computer analysis? If so, it would sure be nice to study some field strength numbers at various elevation angles as compared to a reference antenna such as a vertical over good or perfect ground. I presume this antenna is omni directional and, therefore, azimuth readings are all the same.
Thanks for sharing your data with us. This is the kind of input we need.
73,
Bob, W7KWS
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by W7IQ on August 25, 2002
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Let me inject a bit of my logic here. With my luck in building all things electrical, I can assure you that this antenna is NOT going to work!
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by KB4QAA on August 25, 2002
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-Anything will work as an antenna, even a light bulb. And, if it meets your needs, then it is an adequate antenna.
-These so-called EH antennas are nothing earthshaking, nor particularly efficient. After reviewing all the claims and comments and "theory", I think that they are vertical dipoles with really wide elements, similar to an Isotron or MFJ antenna. The EH theory claims are bogus, I wish they were true.
-Performance is not great, but it works. The basic 20M 2.5 inch diameter antenna appears to be about 6dB below my tuned 20M Hygain Vertical (mounted inside the stairwell of my appartment). And note, that it was usually 2-3 dB below a tuned 20M Bazooka Dipole when I had an antenna farm outside.
-Regarding the comment above "noise level is absent"...no kidding, it is a really deaf antenna.
-Re: "no EMI"... bull, this thing lit up my shack like nothing I've ever seen in 22+ years. The later versions with the two internal isolation coils may help prevent this, and I plan to experiment with these modifications. I had to use a Radio Works Line Isolator just to make the antenna useable. BTW, this antenna radiates down the line like mad, and made it nearly impossible to get a reliable SWR reading.
-Nonetheless, I am forced to live in an apartment for the moment and need an antenna that will work 40M/and Civil Air Patrol 4.585 Mhz. I plan to build the full 4.5 inch diameter version with the internal coils as soon as I can get my hands on some copper foil.
*** Will someone please test this on an antenna range and settle the arguments???***
73, Bill
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RE: Small EH Antenna
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by KA1OGM on August 25, 2002
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Bill,
Consider using aluminum roof flashing for the plates. This stuff is available at any Home Depot at very reasonable prices, and comes in rolls anywhere from 6" to 20" wide. Two of the round "Quaker Oats" boxes makes a great form for the 40m, since they are exactly 4" in diameter.
Coil efficiency is best with bare solid copper wire or soft copper tubing, but doesn't suffer too much if you use white insulated solid copper instead. Colored insulation, especially black, affects coil efficiency because of carbon in the coloring. The same is even more important with PVC pipe used for the forms (don't use the black stuff, or the grey electrical conduit stuff). Spacing coils at one diameter will tend to be better than tightly winding coils with no spacing. The test of efficiency for coils on these antennas is to pump some power into them for a few minutes, then see if anything gets warm.
Simple two cylinder plus coil and link coupler style antennas can be made that do not evidence any slightest heating with full legal output, but you'll never know if the thing really has that level of efficiency if you don't do the "smoke test". The chances are that any disappointments people have with these will most likely show heat with only 50 or 100 watts CW after a couple of minutes.
Jeff Barnard
KA1OGM
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RE: Small EH Antenna
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by WX4O on August 25, 2002
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I agree about the range testing. I have an 80 mtr. Isotron and it seems to work pretty well for a small antenna. It appears to me that it is a different version of the same pricipal. John
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RE: Small EH Antenna
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by N0TONE on August 26, 2002
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W7IQ, I am pleased that my luck seems to be better than yours.
While I doubt the claims that it works on any different principles than other antennas, I have built several antennas with form factors similar to the antenna described here. And they do work. Do they beat a full-sized antenna? Absolutely not.
The best you can hope for with a short antenna is 100% efficiency. The nature of the tradeoffs you are working with are best understood if your efforts are aimed at achieving efficiency, and nothing else.
A broadcast engineer noted to me once that when you build an antenna close to full size, you can make a lot of mistakes, and still have an antenna that performs within a few dB of optimum. However, the same error made with a short antenna can render it useless. 12 gauge wire has no place in a short dipole, but is far larger than truly required for a half wave dipole. Similarly, a matching capacitor built from RG-8 may serve well in a gamma match when the antenna element is 1/2 wave long, but if the element is but 5% of a wavelength, then a coaxial cable capacitor should be avoided like the plague.
A full-size vertical exhibits gain over a theoretic isotropic radiator. This is becuase the vertical does not have any radiation straight up, instead, that energy is directed horizonatally outward. And, with a 1/4 wave vertical, a certain amount of compression of the horizontal lobe takes place, which means more of the radiated power heads toward the horizon than one might otherwise expect, and we achieve "gain". Of course, NO antenna provides amplification. Gain is purely a result of the antenna directing LESS energy in some directions, and favoring other directions.
From that description comes the expected results of this small antenna. Any antenna which is a small percentage of a wavelength long approaches the performance of an ideal isotropic radiator. I don't know that this antenna has any radiation straight up, but it is certain that its main horizontal lobe is wider than one produced by a 1/4 wave vertical. Therefore, even at 100% efficiency, one can expect the radiation at some elevation angles to be a few dB below that of a full sized vertical. The radiation at other angles (which may or may not be useful angles), however, may be higher.
Andrew descrbibes this antenna as a physically short fat dipole, and that's probably a good way to view it. With this model in mind, NEC would predict the feedpoint impedance to be a very small resistance in series with a large capacitive reactance. Your matching network needs to tune out the capacitance and transform to close to 50 ohms. Once the capacitance has been nulled out, you will have extremely high currents at the antenna feedpoint. It only takes a few tenths of an ohm of resistance to have a major on the performance of such an antenna.
One of the short fat dipoles which I constructed gave me disappointing results. I then applied the CW test. I fed it with 100 watts of RF for a few minutes, then disconnected the transmitter, and checked to see what got warm. My 8 gauge wires which led to the two cylinders were just warm to the touch. I had no idea if that meant they were dissipating two watts or 90 watts, though. I replaced the 8 gauge wires with 1/2" soft-drawn copper. Without changing my tuning network, I immediately was greeted with stronger received signals, and was able to make some QSOs. The reduction in loss in the feed system actually caused a change in the feedpoint impedance, and once I re-tuned the matching network, I even got better results.
For local QSOs (less than 200 miles on 80 meters), my short fat vertical dipole provides better results than my 1/4 wave vertical. For anything further than 500 miles, the 1/4 wave vertical is superior.
But, you can believe this antenna to be deaf very easily, as it is extremely narrowband compared to anything full size. If tuned for 3830 kHz, for instance (the frequency of many local contest club nets), I am utterly unable to hear anything on 3905, where there's a traffic net. I must retune the matching network. That is one litmus test of a small antenna's efficiency. If it's efficient, and you're using LC matching, then it WILL be narrow.
Anybody who's used a low frequency hamstik on their car has experienced this particular phenomenon.
I agree with several others. A good design, yes, if you keep your conductor diameters large. A new mode of antenna? No.
AM
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Small EH Antenna
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by W5LF on August 27, 2002
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Anyone hear of a magnetic loop? 1/4th wavelength or smaller in total diameter, usually they are 1/10th or so. AEA made one, MFJ makes two, German and other companies make them commercially into the thousands of dollars, etc. they work on the same magnetic principle that the CCA, DDA etc magnetic antennas do, the magnetic field of the radio wave and not the electrical. A diapole has both but it was made for the electrical field (but still has its magnetic field). My lawn sprinklers never were bothered with my dipole but came on every time I transmitted with my CFA! (until I put some toroids on its cables). No one is re-writing theory here, no new laws written or old ones discarded. I personally haven't made a network (tuner section) that made me happy with my DDA antenna which stood about 14" high and 4" diameter. However, my 10' circumference loop made from 2" copper pipe (about 3' diameter) using a 15-500pf vacuum variable works wonderfully from 6.5 to 26.5 mhz (too much capacitance for 10 meters). its top performer for 20-15 meters and ok on 40 where its efficiency is down.
Don't write anything off until you spend alot of time with it. There are VERY qualified authors and engineers studying and making these. One thing you can't absolutely ever forget, component quality is a absolute requirement with any magnetic antenna. With a radiation resistance of .01 ohm or less, you get very high voltages (my magnetic loop gives me about 4.7kv on the capacitor at 7 mhz) and current. Standard capacitors are out as wiper connections to the rotor (and resistance between plate connections, etc) all have resistive losses, vacuum variables or items such as butterfly capacitors are in, but only if the butterfly caps plates are welded together! See what I mean? Different requirements for this stuff but it can be very fun to mess with.
My loop antenna at 10 feet operates as well as my dipole at 30 and the loop has almost no noise. I compare it to a beverage for a low noise floor.
Experiment! Ham radio can be fun again if you do.
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Small EH Antenna
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by W9WHE on August 27, 2002
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I have a Corbamite rubber duckie on my HT.
The Corbamite coil multiplies whatever power is fed to it by a factor of Ten. Thus, my 5 watt HT has, in effect, a 10 db amplifier, so I can consistently work repeaters 100 miles away (and more) full quieting, with just my 5 watt HT and rubber duckie.
Now, I'm making and selling "Small EH antennas" made from Corbamite. With a Corbamite "EH antenna" you will be able to work ZL, VK and RARE DX with only a few milliwatts.
Any takers?
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RE: Small EH Antenna
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by VK4JAM on August 28, 2002
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Hi Bob,
I have run simulation for several of the designs presented on the referenced web pages, and have also sent / received an e-mail from Jack W0KPH. Jack has suggested that I “think about the relationship of the fields.... and how a conventional antenna actually radiates.”. Well I have tried this … but I guess I just cannot leave behind all my training / experience in "normal" antenna theory. Please don’t get me wrong – I believe the antenna presented here is great – it’s just that I can not make the leap to a “new” theory at this time.
Anyway... I still see the antenna as a fat dipole. The simulations show that making the dipole short does not seem to change the radiation pattern significantly, however there is a need for a good matching network such as that described. I have run simulations using both the public domain NEC software (refer the NEC Archive at http://www.qsl.net/wb6tpu/swindex.html - NEC.XLS by Peter Ward, VK2VCI recommended) and YagiMax (developed by By Lew Gordon, K4VX).
The results from both give similar results even though the ways the calculations are performed are a little different. My suggestion is to get the copy of the software and try several simulations. YagiMax is by far the easiest to use. If you send me an e-mail directly I will send you the YagiMax files that Lew sent me.
The use of several of the “short fat” dipoles in a Broadside array may prove very interesting. Low cost, simple with a little “punch”. Try the modelling the antenna and you will see what I mean.
73's
Andrew
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RE: Small EH Antenna
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by WB2WIK on August 28, 2002
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W9WHE: The Corbamite antennas sound great. Please send me one dozen of them, I'll pay you via Waitpal.
"We the unwilling, led by the unknowing, are doing the impossible for the ungrateful. We've been doing so much with so little for so long, that we're now qualified to do anything with nothing."
WB2WIK/6
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Small EH Antenna -- bogus?
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by K1LI on August 28, 2002
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It's my recollection from what I learned of Maxwell's equations in college that an electromagnetic field arises when a charge accelerates, the way electrons sinusoidally accelerate on a "Hertzian" antenna. Thus, an electromagnetic field is MORE than the sum of an electric field and a magnetic field, separately generated. It is for this reason that I don't believe the CFA hype. Any physicists out there who can comment?
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