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[Articles Home]  [Add Article]  

Your First HF Dipole

Phil Chambley, Sr. (K4DPK) on June 16, 2010
View comments about this article!

Your First HF Dipole

What you need to know to make your first antenna work.

A few weeks ago I posted a little recipe on the Elmers forum, showing how a simple single-band, coax-fed HF dipole antenna could be constructed, with the least possible investment in time and study. My thinking was and remains that the new ham wants to get on the air as quickly and effectively as possible, and then, if he stays with it, learn more about how antennas actually work.

There were a great many comments and much discussion about resonance, matching and about other antenna types that I know youíll find helpful. I encourage you to read those in the ďTower TalkĒ forum, under the heading ďPutting up HF DipolesĒ.

It was at some point suggested this should have been an article, so I will now attempt to correct that mistake and to add some other simple, non-technical suggestions. I hope new hams are able to benefit from this writing, and I hope the more experienced of you will add helpful suggestions youíve picked up along the way.

The original recipe (more or less):

Putting Up HF Dipoles

This is going to be a mono-band antenna one-half wavelength long, fed in the center with 50 ohm coaxial cable. This is probably the most common antenna used on the ham bands today, and it is useful for both local and DX work.

Hereís how to do it:

1. Decide what frequency you want to have in the middle of your planned operating range.

2. Divide the number 468 by that frequency in MegaHertz. The result will be the overall length (in feet) the antenna should be, between the ends of the loops on the extreme ends of the antenna, where the wire passes through the insulators.

3. Take notice that the overall length is just a little longer than the sum of the two wires from inside loop to outside loop. That's because the part of the feedline that attaches to the middle insulator (where itís fed) is antenna, too. The length of the antenna is the total length from where the wire passes through the insulator on one end, to where the wire passes through the insulator on the far end. If you want to be really precise on the higher bands, add an inch or so for the loop going through the insulator. Each side of center will be one-half the total length of wire.

4. Cut the wire for each side a little longer than the formula says. Adjustment will be required, and it's easier to remove wire than it is to add. By ďa little longerĒ, I mean ten inches or so on 20 meters, proportionally more on the lower bands, less on the higher. Whatever actual finished length you have, WRITE IT DOWN.

5. There are several good reasons to use a 1:1 balun or a ferrite choke balun at the feed point. Without going into detail, suffice to say using one will help in terms of telephone and other RF interference, and will probably help keep RF off your microphone.

6. Put the thing in the air as high as you can. Then find the frequency where the SWR is lowest. This might be at the bottom of the CW band or at the top of the phone portion. It doesnít matter. RECORD that frequency.

7. Then take the actual length of the antenna (you wrote it down, remember?) and multiply it by the frequency (in MHz) of the lowest SWR. That number will be your new constant, to replace 468.

8. Divide the new constant by the frequency you want to have in the middle of your preferred range. This is the length the antenna should be. Now you need to adjust the one you have in the air to this length. You might find itís easier to simply add or take away equal lengths on either side near the center insulator rather than on either end.

9. After doing this haul the antenna back up into position. It should now give you the lowest SWR at the desired frequency.

If for some reason you later want to trim an HF wire antenna (say, you decide to move to a different band segment), donít waste your time cutting a half-inch at a whack. You can estimate how much to cut or add based on the band and how far you have to move it.

For example, compare 468/ 14.0 = 33.42 ft with 468 / 14.35 = 32.61 ft , so only about 10 inches to move the width of the entire band on 20 meters.

On 75/80 meters, the difference between the band extreme edges is better than sixteen feet.

So you see, if you think about it and plan ahead, itíll sure simplify getting your dipole up right and do it in a hurry.

Now for some more stuff.

Insulators:

Obviously insulators need to be non-conductive; otherwise they wouldnít be called insulators. You can buy porcelain or plastic insulators at most hardware stores, including Tractor Supply, Home Depot and Ace Hardware. Basically, they just need to be a piece of plastic or porcelain about 2-4 inches long with a hole in one end for the wire and a hole in the other end for a rope. Iíve made a lot of them from ľ inch Plexiglas. Years ago when glass Coke bottles were common, you could pop the rings off the top of íem. Iíve used those glass rings for low-power antenna insulators. The point is, you just have to be resourceful. Consider the power youíll be running and the mechanical stress the insulator will need to withstand. Anything fairly close will work.

Coaxial Cable:

Coaxial cables are grouped in classifications of an electrical property called impedance. It is this number which gives us an indication as to where along the length of a piece of wire the transmission line should be attached to obtain optimum transfer of power. Impedance varies along the length of the antenna wire, and has to do with the length of the wire and the ratio of voltage to current at particular points along that wire. There is a wealth of information available on this subject when you are ready.

The most common coaxial lines used in feeding ham antennas are probably the 50-ohm variety. Over the years, this family has been called both 50 and 52 ohm, but we are talking about the same thing.

Some of the common 50-ohm lines are RG-8U, RG-8X, RG-213, 9913 and a couple of small ones for low power, RG-174 and RG-58. Usually, the smaller ones are less expensive but they also have greater loss. That is, not as much of the transmitted energy reaches the antenna to be radiated, as compared to their larger kin. There are charts for comparison in the ARRL Handbook and on the Internet.

It is worthy of note that most manufacturers have adopted 50 ohms for the design output impedance of modern transceivers.

Baluns:

The word balun is a combination of the words BALanced and UNbalanced. As the name hints, itís a device that connects a balanced system to an unbalanced one.

Baluns are often used to connect a balanced antenna (like the half-wave dipole) to an un-balanced feedline (like the coax). The balun, among other things, helps prevent current flowing on the outside of the coax. Otherwise, when this current (called common-mode current) appears on the outside of the shield, the feedline behaves as if it were an antenna. There are several reasons why this isnít what we want to have happen. If the feedline is behaving like an antenna, and it passes near a phone line on the way inside, you will probably interfere with the telephone. Since antennas work both ways, if the feedline comes close to a noisy power line, chances are itíll pick up the noise and bring it inside to the receiver.

Thatís not to say antennas wonít work without a balun. Quite the contrary, but it generally will be true youíll have fewer problems with noise and interference if you take steps to avoid current on the outside of the feedline.

Some baluns have the ability to transform to a higher or lower impedance. This has to do with the ratio of turns contained in the windings of the balun. Youíll see baluns called 1:1 or 4:1, etc. This is the ratio of impedances the balun is intended to connect. For instance, if one wanted to connect a 450-ohm balanced feedline to a 50-ohm unbalanced line, he would select a 9:1 balun. You will learn later this is a convenient way (for instance) to bring a balanced open wire line from a multi-band antenna into the house, using a short length of coax.

In our case however, since the center of a half-wave dipole is closer to 50 ohms impedance than it is to most other standard feedlines, and since we are using 50 ohm coax, we need to have a 1:1 balun.

Wire:

Antenna wire can be almost anything at all, so long as it will support the weight of the antenna, conduct electricity, withstand expected wind and ice load, and lend itself to a good long-term low-resistance electrical connection. Usually this means a copper wire of sufficient size, although it wouldnít surprise me to hear of someoneís having used barbed wire. Iím sure Iíve come pretty close in my early years.

Antenna wire for HF can be new wire, or it can be pieces of dissimilar wire properly soldered together. What matters is the length, and as mentioned earlier, its mechanical strength. It doesnít matter if the wire is insulated or bare, solid, stranded or a mix of them allÖ.. If you follow the steps given earlier about finding a new constant replacement for 468, itíll all turn out well. Just make sure your connections are OK.

Measuring:

Measure the antenna length from one outside end to the other, counting the center insulator as part of that length. If you have loops that go through the end insulators, and the ends are wrapped back around the wire, then measure from the outside ends of the loops.

Donít get carried away with precision. There is no need for great pains to be taken with the measurements on HF antennas. On two meters, a half wave antenna is around 38 inches, and obviously an inch is an appreciable percentage. On eighty meters, though, an inch will only ďmoveĒ the antenna about three kHz.

As mentioned elsewhere, it takes around fifteen feet to change from one end of the 75-80m band to the other. Obviously, the higher in frequency, the greater the measurement precision required and vice-versa.

Putting it in the Air:

There are as many ways to hang a wire as there are situations, but in general, to pull the antenna up you first must have a rope already over a tree limb, yardarm, post, pole or some other elevated stationary point.

The simplest way is to just throw a rope over a limb. Remember the old Gene Autry movies? Well that would work, but we want to be a little higher off the ground than was customary in dealing with horse thieves.

Usually, itís easier to put a pilot line of, say, 15-20 lb. monofilament fishing line over the limb, pull the rope up with that, and then pull the antenna with the rope.

You can put the pilot line up in a number of ways:

Throw it by hand with a weight on the end
Use a fishing/spinning/casting rod
Slingshot
Bow and arrow
Potato gun

There are lots of others that I canít think of right now, and these can all be used in combination or with great modification and still work, but you get the idea. One caution, thoughÖ.Donít be tempted to use your socket wrenches for weights. Sometimes, the line becomes tangled in the tree, and you donít get your weight back. Thereís a nice house over in Rome GA with a complete socket set dangling high up in the pines. I wonder if the new owners ever noticed.

Iíve learned that a 2-3 oz lead pyramid weight painted fluorescent orange works really well. It comes down through the limbs nicely and itís easy to spot in the brush.

Anyway, once you get the line over the tree, remove the weight, tie on the rope and pull it up through the tree. Then tie on the antenna and haul it up.

Donít EVER throw wires or anything else over power lines, and donít ever haul antennas up over the top of power drop wires. Thatís as good a way as I know to make a complete ash of yourself.

Rope:

Twisted or braided polyester in either 3/16Ē or ľĒ diameter size is probably the best general-purpose rope for putting up antennas around here, but up ďNawthĒ folks may need something a little more substantial.

Polyester has good UV resistance and doesnít rot or degrade over time. It also has better abrasion resistance than many other ropes, and has normal moisture content of only 0.4%, compared to nylon 6,6 having 4.4%. Dacron is DuPontís registered name for polyester. Most of these ropes are available in colors, and OD or black is best. Your wife will explain this to you if you hang a new white rope across the front lawn.

Nylon is second choice. Polypropylene or olefins are awful and should be avoided.

Whenever you cut any synthetic (thermoplastic) rope, itís a good idea to melt the cut end together, so it wonít fray. If the end of the rope catches on fire, donít try to snuff it out with your fingers. Youíll see why if you try it.

Pulleys:

Sometimes, situations present the need for a pulley, but pulleys are not a good idea when putting up wire antennas. Use ceramic egg insulators, or ďJohnny ballĒ insulators instead.

Pulleys can rust if they are the wrong material, or the rope can jump off the wheel and jam itself between the wheel and the housing. Whenever this happens, youíll tear the whole thing down and start over, at least on that end.

Ceramic insulators are very slick, very tough and have no moving parts. I have some up that have been in use as pulleys for over twenty years with no problems.

Shape of the antenna:

Dipole antennas usually are installed in either flat top or inverted V configurations. On the HF bands, though, antenna dimensions sometimes exceed the accommodation typical lot sizes offer, so itís occasionally necessary to stray from the ideal.

OK, now there are a few things you need to know about the electrical properties of the half-wave antenna. You should read up on antennas and understand why these are true.

1. The electrical current is highest at the center and lowest at the ends.

2. The voltage is lowest at the center, and highest at the ends.

3. It is the high-current portion of the antenna that radiates the most.

Reasons no. 1 and 2 show why we can feed the dipole in the center with a low-impedance line. The impedance is lowest there on the band itís cut for, and at practical heights it is very near the impedance of the 52 ohm coax we are going to use for this single-band dipole. (Later, you can learn how to build multi-band antennas fed with open wire line.)

You can see from this information how important it is to have as much of the center portion at the highest possible point (Reason #3), but it is also permissible to allow the ends to droop or even hang straight down if need be. Donít have the ends so low the neighborhood kids or anyone else can touch them. There are very dangerous voltages present (Reason #2).

Some liberty can be taken with whether the wire follows a straight path. I suspect there are a lot of 160m inverted Ws and Zs out there, and they still, for the most part, work.

The point here is to get the antenna as high as you can, as straight as you can, but if you need to, there is some ďwiggle roomĒ.

Just be safe, stay away from power lines and think about what youíre doing so you donít unwittingly set a trap for someone.

Coax connectors:

It is very likely that most of the problems experienced by new hams (if they find their newly-erected first antenna wonít work), are due to improperly assembled coax connectors.

Always use good high-quality connectors. If you must use the cheap nickel- plated stuff, use a small file and remove the plating around the holes in the inner barrel. Tin these well with solder before inserting the coax.

Examine the braid closely after removing the insulation. Make sure no stray shield filaments are left that might touch the inner conductor. I usually tin the braid very lightly before pushing it into the barrel. (Donít forget to put the outer body on the coax before installing the inner barrel).

Use a good hot iron. 250-300 watts is ideal. That way you can get the connection heated up in a very small area, solder it and take the iron away before the heat migrates very far into the coax insulation. If you leave the heat on the connector or coax very long, youíre gonna melt something important.

A good friend reminded me of a neat trick. Keep a damp sponge or cloth handy to quickly cool the connector after soldering.

Once you have the connectors on the line, use an ohmmeter to check continuity of the shield and inner connections, and also make sure you donít have a short between the inner and outer conductor.

Do this without the balun connected. Some configurations of wound baluns show a short to a DC ohmmeter, but they are perfectly OK at radio frequencies. You can see why by reading up on baluns in any good electronics/ham radio handbook.

Weatherproofing:

A lot of folks use a putty-type coax sealant on their connectors. I donít because itís very difficult to remove and separate the connection after itís been on there a while.

I use Scotch 33 black plastic tape over the connectors, stretching a couple of layers over the tightened connector and the adjacent coax, in order to prevent any possible moisture entrance. On the final wrap of tape, I leave a tab sticking out and fold the tape on itself so I can find the end later if I want to remove it.

I use RTV on coax when there is an exposed raw braid end without a connector, such as would occur when attaching coax to a dipole without use of a balun.

Conclusion:

Remember, your license is a license to learn. Study the handbooks and antenna manuals, and youíll understand how what youíve constructed works.

Get yourself an ARRL Antenna Handbook, and go to places like www.w8ji.com and start reading. Many of the Elmers on e-ham and elsewhere on the web can explain the details just as fast as you can absorb them. Donít pass up these valuable resources when you get over the excitement of the first few contacts and start your serious education.

There are hundreds of different antennas, and they satisfy uses ranging from local to DX, gain to low-noise reception, directional and mobile, simple and exotic. Antennas offer a wonderful place to begin learning and experimenting as you grow in ham radio. All weíve done here is scratch the surface with of the simplest of all.

Good luck.

Phil C. Sr.
k4dpk

Member Comments:
This article has expired. No more comments may be added.
 
Your First HF Dipole  
by W9PMZ on June 16, 2010 Mail this to a friend!
this is probably your second dipole.

the first dipole is usually put together in 10 minutes to get on the air!

73,

carl - w9pmz
 
Your First HF Dipole  
by AD5X on June 16, 2010 Mail this to a friend!
I use Liquid Electrical Tape to waterproof connectors and connections. Works great, and peels off easily if you need to change something.

Phil - AD5X
 
RE: Your First HF Dipole  
by SWMAN on June 16, 2010 Mail this to a friend!
Phil,
Great article with lots of good info. I will be making some dipoles in the next few weeks so this will come in very handy.I will be taking my Tech and General test on July 5th and maybe get on the air soon. Thanks for taking the time to write. 73. Jim
 
Your First HF Dipole  
by KB2DHG on June 16, 2010 Mail this to a friend!
A very nice article and for the beginner it is very well understood. I have experamented with many types of home brew wire antennas through my years in the hobby.
I think going through all that for just one band is not worth it when with the same effort you can build a multi band dipole like the famed G5RV. I use this antenna and have worked the world on all bands except 160!
Very simple construction. 2 secetions of #14 copper wire cut at 51 feet each (yes add a couple of more inches for twisting around the insulators) Then I used 31 feet of 450 ohm ladder line. Connected the 50ohm coax (NO BALUN) to the ladder line. I got the center up about 32 feet installed as an inverted V.
Thats it! And it works GREAT! ON 10,15, 20,30,40 and 80 meters I can tune swr to between 2.0-1.1 all day long!
 
Your First HF Dipole  
by K9CTB on June 16, 2010 Mail this to a friend!
Very good article, Phil!!! Bravo!!

I got a chuckle out of the idea of using barbed wire ... then I thought ... if nothing else, it's practical, and nobody would get hurt if it's up high enough. I wonder if it's solderable? Hmmmmm....! :) Somewhere, somebody must have tried it ... if not actually operating on it today!

73 de Neil
K9CTB
 
RE: Your First HF Dipole  
by N2EY on June 16, 2010 Mail this to a friend!
Great article, Phil. We need more like this!

Couple of very minor points:

1) For most HF dipole applications, good RG-8X is perfectly adequate. Bigger coax is only needed for long runs or high power.

2) Insulators can be made from scraps of PVC pipe, Corian or similar counter-top material, etc.

3) A propane torch with soldering-tip attachment does a great job *outdoors* on heavy soldering jobs. But watch where the flame goes!

73 es TNX de Jim, N2EY
 
RE: Your First HF Dipole  
by K0FF on June 16, 2010 Mail this to a friend!
"2. Divide the number 468 by that frequency in MegaHertz."

Older radios, sometimes called "Boatanchors" do not have MegaHertz, only MegaCycles. Here is a handy chart to convert MegaCycles to MegaHertz.

http://www.eham.net/articles/4323

Geo>K0FF
 
Your First HF Dipole  
by W1ITT on June 16, 2010 Mail this to a friend!
Good stuff, Phil ! In the "weatherproofing" section, I'd add the caution that some RTV sealers evolve acetic acid, with a vinegar smell, as they cure. Those sealers are corrosive to coax conductors, and should be avoided.
73 de Norm W1ITT
 
RE: Your First HF Dipole  
by KA4KOE on June 16, 2010 Mail this to a friend!
Use WD-1T communications wire, surplus in big quantities from Ebay CHEAP. Two conductor, very very strong, insulation so tuff it will dull a knife stripping it. The wire is two conductors (each about 200 lb breaking strength), so strip the ends and solder the wires together. The wire is steel reinforced copper, but it WILL solder if you use good heat.

Basically, the WD-1T is nearly indestructible. Several doubled up lengths can pull a car out of ditch.

Feed with TWINLEAD!!! and connect to a balanced tuner. OR, go to a 4-1 balun on the entry point and convert to coax for a final run of 20 feet or less to minimize losses, and feed with a conventional tuner. Using twinlead cut for the lowest band will give you all band operation. Its the classic doublet used by everyone before coax became popular after WW2.

Just my 3.432 cents worth.

Philip
KA4KOE
 
RE: Your First HF Dipole  
by W4VR on June 16, 2010 Mail this to a friend!
You really don't need end insulators if you use weed wacker cord for supporting ropes. It's also very resilient and won't wear out over tree branches with tree sway. Get at least the 0.1" diameter cord. Color seems to make a difference with regard to UV breakdown...green lasts longer...black and clear don't last as long.
 
Your First HF Dipole  
by K0IC on June 16, 2010 Mail this to a friend!
Barbed wire is illegal in my small town. One needs to check local laws before using it. I have used steel wire that was not barbed however.

I like the multi-purpose antennas. The 102-foot dipole feed with balanced feed line with a tuner is a good standby. My current antenna is 180-foot dog legged antenna with a hundred foot 24-gauge hookup wire wrapped around the garage. It loads real easy and works all over North America on 20 meters. I feed it through a 4:1 current bond with one end at earth ground. It is also NVIS which has its place. I plan to add a 6BTV Hustler vertical when funds allow as that should be a FB DX antenna. I plan to add a neon gas protector for static.

My first dipole was a World Radio Labs antenna made for 80-40-15 meters. It worked OK as long as I used tube radios that drained off static. I almost was electrocuted in a snow storm when I took it off my Drake TR-3.
 
Your First HF Dipole  
by K1WJ on June 16, 2010 Mail this to a friend!

Phil, thanks for taking the time to write this article, Many will find it useful I'm sure. Pound for pound the 1/2w dipole is #1....73 K1WJ David
 
Your First HF Dipole  
by G0GQK on June 16, 2010 Mail this to a friend!
Or buy a G5RV from a hamfest !

G0GQK
 
RE: Your First HF Dipole  
by N4KC on June 16, 2010 Mail this to a friend!
Phil, you are an Elmer par excellence! We assume newcomers to the hobby know what they need to know to put together a dipole and get on the air with it. Not all do...until now!

FWIW, here is my article from a while back on what I consider the top five "get on the air quickly" antennas. Hope it helps.

http://www.eham.net/articles/21270

Don Keith N4KC
www.n4kc.com
www.donkeith.com
www.n4kc.blogspot.com
 
RE: Your First HF Dipole  
by LNXAUTHOR on June 16, 2010 Mail this to a friend!
without fail, the first dipole you erect will outperform (and outlast) all subsequent dipoles

the cheapest home brew dipole will always outperform a commercial dipole

cheap (surplus) wire beats commercial elements

neighbors never complain about wire dipoles

 
RE: Your First HF Dipole  
by K5TEN on June 16, 2010 Mail this to a friend!
VERY well done article! A MUST READ for ALL new hams!

73

Bruce
 
RE: Your First HF Dipole  
by WX7G on June 16, 2010 Mail this to a friend!
I don't use end insulators at the 100 watt level. The poly rope makes a fine insulator.
 
RE: Your First HF Dipole  
by WB2WIK on June 16, 2010 Mail this to a friend!
>RE: Your First HF Dipole Reply
by WX7G on June 16, 2010 Mail this to a friend!
I don't use end insulators at the 100 watt level. The poly rope makes a fine insulator.<

In the dry summer WX, that works fine. I've done this lots of times.

Then, in the winter when it rains...not so good.

I've caused double braided Dacron antenna rope to "burn up" right where it attaches to the wires when the rope is wet and I transmit. The voltage gradient is evidently so high, that even wet rope will either burn or melt (Dacron kind of "melts").

I've also burned up plastic end insulators when they're wet. Never seems to happen when they're dry.

I use only glass or glazed ceramic/porcelain now. Tired of finding flaming insulators and ropes in the yard. :-P
 
RE: Your First HF Dipole  
by W7ETA on June 16, 2010 Mail this to a friend!
Fantastic prose.

Well constructed; from top to bottom, easy to follow article.

U da man!

73
Bob
 
Your First HF Dipole  
by WX4R on June 16, 2010 Mail this to a friend!
Good article. I would use a C of 492 and trim.
 
RE: Your First HF Dipole  
by KB2VUQ on June 16, 2010 Mail this to a friend!
I cut it twice, but it's still too short!
 
Your First HF Dipole  
by WO4V on June 16, 2010 Mail this to a friend!
Aluminum electric fence wire makes an excellent and cheap antenna. You can get a 1/4 mile spool of it for about 25 bucks at farm supply stores. Durable as heck and if it falls down, you can simply crumple it up and recycle it like a soda can! Attach your feedline to it with split bolts (available at Lowes in the electrical isle) of with the bolts available in farm supply stores to attach the electric fence chargers to the fence. While you're at it, stop at your farmer's co-op and pick up a package of ceramic fence insulators...heavy duty and about 10 bucks a dozen...use them for end and center insulators. Farm supply stores that sell fencing supplies will usually have this stuff. Also, pick up a bag of "Gripples", a really handy little gadget that allows you to join two pieces of wire in a jiffy and makes a strong joint that is re-usable later on.

I have been using it for years and it always comes through in all kinds of weather, and outlasts copper and copper-plated steel by a long shot.

For end ropes (over the tree limb)...use 1/8 inch "snare" or "aircraft" cable. You can get this in either galvanized or stainless. Lasts forever and usually comes with the crimp-on ferrules to make loops and so forth (gripples work on this stuff, too). I used to use ropes, etc. but got tired of replacing them a couple of times a year. You can find it on Ebay cheap...Yeah, and for you purists, I know it de-tunes your antenna somewhat... So adapt, improvise, and overcome...it might require you to alter the length of your antenna slightly to compensate. BTW, you can also use this stuff for the antenna itself if you need a REALLY heavy duty antenna. Works fine but is not as conductive as aluminum, and will have a slightly different velocity factor, but I doubt if you can notice the difference on either transmit or receive.

Dave
 
RE: Your First HF Dipole  
by W7ETA on June 16, 2010 Mail this to a friend!
"7. Then take the actual length of the antenna (you wrote it down, remember?) and multiply it by the frequency (in MHz) of the lowest SWR. That number will be your new constant, to replace 468."

SO simple!

I've never seen that handy tip before.

73
Bob
 
Your First HF Dipole  
by N9PUZ on June 17, 2010 Mail this to a friend!
Nice article Phil. While I don't necessarily disagree with some of the comments suggesting "improvements" I think it's always good to have a nice, simple, baseline antenna. We all know a simple dipole works pretty well. It's a great antenna to have up as a reference when you're experimenting with other types or evalating your latest purchase.

73,

Tim N9PUZ
 
Your First HF Dipole  
by N6JSX on June 17, 2010 Mail this to a friend!
You do not need to use a balun IF the two legs are near 120 degrees apart. The Reactance will be very near 50 ohms for direct connection to 50 ohm coax.

This is why you want to consider making a dipole into an Inverted V or a lay-down horizontal V (type) beam.

Another point to an inverted V is you can Z back the leg ends if you have space/property constraints - like on 160/80m. The antenna will still work fine.

Inverted V's are by far better and easier to construct and install than dipoles, only one high point is needed at the apex vs three of a dipole.
 
RE: Your First HF Dipole  
by K7LRB on June 17, 2010 Mail this to a friend!
I'm still amazed by people who think a G5RV is a multi-band antenna!

73,
de Larry
 
RE: Your First HF Dipole  
by K7LRB on June 17, 2010 Mail this to a friend!
I'm still amazed by people who think a G5RV is a multi-band antenna!

73,
de Larry
 
RE: Your First HF Dipole  
by K7LRB on June 17, 2010 Mail this to a friend!
I'm still amazed by people who think a G5RV is a multi-band antenna!

73,
de Larry
 
RE: Your First HF Dipole  
by K7LRB on June 17, 2010 Mail this to a friend!
I'm still amazed by people who think a G5RV is a multi-band antenna!

73,
de Larry
 
RE: Your First HF Dipole  
by K7LRB on June 17, 2010 Mail this to a friend!
I'm still amazed by people who think a G5RV is a multi-band antenna!

73,
de Larry
 
RE: Your First HF Dipole  
by K7LRB on June 17, 2010 Mail this to a friend!
I'm still amazed by people who think a G5RV is a multi-band antenna!

73,
de Larry
 
RE: Your First HF Dipole  
by K7LRB on June 17, 2010 Mail this to a friend!
I'm still amazed by people who think a G5RV is a multi-band antenna!

73,
de Larry
 
RE: Your First HF Dipole  
by K7LRB on June 17, 2010 Mail this to a friend!
I'm still amazed by people who think a G5RV is a multi-band antenna!

73,
de Larry
 
RE: Your First HF Dipole  
by K7LRB on June 17, 2010 Mail this to a friend!
I'm still amazed by people who think a G5RV is a multi-band antenna!

73,
de Larry
 
RE: Your First HF Dipole  
by K7LRB on June 17, 2010 Mail this to a friend!
I'm still amazed by people who think a G5RV is a multi-band antenna!

73,
de Larry
 
RE: Your First HF Dipole  
by W8AAZ on June 17, 2010 Mail this to a friend!
Larry must stutter? Must be a CW man then. Anyway, my best antenna I ever had for low bands was a form of dipole called the inverted Vee. Fed in the center with a balun and a couple of traps so it worked on 75 and 40. Had it up really high in the center. Was a fantastic signal on those bands with a barefoot rig. Never since have I had the space to put a large dipole up or get one up high. My current dipole now is pretty low. I used to be able to work em if I could hear em. Now it is about half and half. Either hams ignore me more than they used to or height is everything!
 
RE: Your First HF Dipole  
by N3OX on June 17, 2010 Mail this to a friend!
"I'm still amazed by people who think a G5RV is a multi-band antenna!
"

I'm still amazed by people who insist they aren't despite the availability of very clear analysis and testing showing that they are good on multiple bands.

http://www.w8ji.com/g5rv_facts.htm

http://vk1od.net/antenna/G5RV/optimising.htm

They're not ALL band antennas. But they are actually a multi-band design. And the many variations of commercially available antennas called "G5RV" make them a big trap for new hams. A "G5RV" that shows "naturally low" SWR on most or all of the ham bands is guaranteed to be an efficiency disaster. A G5RV built like the one on W8JI's page won't be.

The major problem with a proper G5RV is prejudice. W8JI says this of on-air comparison tests of a G5RV vs. an 80m dipole, while telling people the G5RV was the dipole and vice versa:

"When I would call each antenna by the opposite name, the antenna I was calling the G5RV was still reported in some negative context about 80% of the time. The remaining percentage again reported no real difference."

It is a multi-band antenna when done properly.

-----

But this is the great thing about a HF dipole as a first antenna. It's easier than almost everything else to do properly, especially if you follow some good advice like this. You CAN'T mess it up because of subtleties with feedline loss. You don't have to worry about the way that a good antenna tuner can "load up" a terrible system just as well as it can "load up" an efficient system.

You build a half-wavelength dipole fed with okay coax and quickly tune it according to this procedure and it will radiate most of the power you apply to the shack end of the coax. That makes it a perfect first antenna. It also makes it a perfect piece of TEST EQUIPMENT. You have some other antenna you want to try? A/B it with your dipole. You *know* the dipole is going to work rather well without testing it against anything, so your first 20m dipole can also be the thing you use to test your *next* antenna against to make sure it's at least as good or better.

73
Dan
 
RE: Your First HF Dipole  
by VE3FMC on June 17, 2010 Mail this to a friend!
One thing I do, which others may find to be a waste of time.

I stretch the wire I am going to use for the legs of dipoles, loops etc.

Reason I do this is that over time the wire will stretch out and droop. It will also change the resonate frequency of the dipole or loop. Not so much on the lower bands but on the higher bands it might change a bit.

I also use insulated wire. That way I can run it through trees which I need to do in order to put up a 75 M dipole.

Plus the insulated wire is quieter in the winter, not as much snow static according to the experts.

The original article was a very good article which should help new comers to the hobby if they find it and take time to read it.

You would not believe how many new hams have no clue when it comes to making a simple dipole.

One other thing, you can add one other bands to the original dipole. Fan dipoles work well, I feed my 75 and 40 meter dipole off the same coax feed line.
 
Your First HF Dipole  
by KU4UV on June 17, 2010 Mail this to a friend!
Whenever 10 meters opens back up again to worldwide propagation on a daily basis, you will be surprised what you can do with a simple dipole antenna and 25 Watts. I built a dipole for a 25-Watt 10 meter mobile transceiver when I first started apartment living. I tied the coax wire to some PVC pipe using electrical tape, basically just so I could move the antenna in the attic if needed. The overall dipole was maybe 20 feet off the ground, laying on the fiberglass insulation of the attic and fed with coax cable. I used a Bencher 1:1 balun on the dipole. I was able to work DX stations with the setup from Lexington, KY. I was also able to work Hawaii several times on 10 meters. The dipole is a great antenna to get on the air quickly and easily.

73,
KU4UV
 
RE: Your First HF Dipole  
by K4DPK on June 17, 2010 Mail this to a friend!
Very good point, and one I forgot to include. Pre-stretching is a very good idea, if you use THHN or other soft insulated wire, or magnet wire.

Another reason I like insulated wire, is when you get ready to change frequency or use the wire in another antenna, the wire is clean and solderable when you peel the insulation away.

Lots of great comments, folks.

Thanks!

Phil C. Sr.
k4dpk
 
Your First HF Dipole  
by K2JVI on June 17, 2010 Mail this to a friend!
I just added a 12/10 meter dipole combination to my antenna farm and its doing a fantastic job on 10 meters, just worked several stations on 10 this evening. I'm not exactly a newcomer(been licensed 31 years), but just to say to the new hams that even us "old timers" still find the dipole a handy antenna to meet a requirement or solve a problem. For my situation, it was to compliment my antenna farm. I have a homemade multiband vertical that works great for 160-15 meters, but noticed the efficiency of the vertical dropped dramatically above 15 meters,hence the addition of the 12/10 dipole. Made mine out of 14 thhn wire, a 1:1 current balun, 2 insulators, 4 PVC pieces (to space the 12 and 10 meter dipoles),RG8 coax and rope to hang it from two trees at about 30' above ground.Just finished up a QSO, short skip to M.O and one to TX.both with good signal reports. One advantage to my situation is the 12/10 dipole is only 19' total length so installation was very simple.
 
RE: Your First HF Dipole  
by NR4C on June 18, 2010 Mail this to a friend!
This is a great article. It will answer 1 out of every 6 questions posted to this site.

Great job....

...bc
 
RE: Your First HF Dipole  
by KB9TMP on June 18, 2010 Mail this to a friend!
The 10 meter dipole that KU4UV talked about is the truth. When I got my Tech Plus upgrade I made a cheap dipole for 10 meters out of discarded Cat 5 cable. Just connected all the wires together at each end and put it up at about 15 feet. My first HF 10 meter contact was KH6DV Kaneohe, Hawaii all the way from southern Indiana. Bottom line, get some wire in the air and start working the airwaves!

73 de KB9TMP
 
Your First HF Dipole  
by KF7ATL on June 18, 2010 Mail this to a friend!
I have been on HF not quite a year now. I made a 40 M dipole to get on the air quickly, and am still using it. I can see why a dipole is recommended for a first antenna: it's easy to make, it's rugged (mine has stayed up all winter), and it works surprisingly well for such a simple antenna. I don't get on the air every day, but to date I have worked 39 states and 3 countries with my simple dipole!
 
RE: Your First HF Dipole  
by W8JI on June 19, 2010 Mail this to a friend!
This comment below is absolutely wrong!!!

"by N6JSX on June 17, 2010
You do not need to use a balun IF the two legs are near 120 degrees apart. The Reactance will be very near 50 ohms for direct connection to 50 ohm coax.

This is why you want to consider making a dipole into an Inverted V or a lay-down horizontal V (type) beam. "

I hope no beginners follow the advice quoted above!!!!


Follow the article.

73 Tom
 
Your First HF Dipole  
by VE4AMN on June 19, 2010 Mail this to a friend!
Nice, complete summary. My finernails thank you for the fold-over tape trick.
 
RE: Your First HF Dipole  
by KY5U on June 19, 2010 Mail this to a friend!
Hey Phil,

Since many have suggested not using insulators and not using coax, can I also not use wire? It would be easier to string support rope from my rig, out my window to a tree and just transmit on that. Would that work as well?
 
Your First HF Dipole  
by K9ZF on June 19, 2010 Mail this to a friend!
Great article Phil!

This is a great "Intro to Amateur Antennas 101" level article :)

I really hope you do a follow up article with making a multi band dipole. I think that is the next logical step. Ie: Amateur Antennas 201...

A good next step would then be loops and verticals.

And then the master level would be phasing verticals, yagis, and computer modeling :)

Fun stuff. Thanks for the great article!

73
Dan
--
Amateur Radio Emergency Service, Clark County Indiana. EM78el
K9ZF /R no budget Rover ***QRP-l #1269 Check out the Rover Resource Page at:
<http://www.qsl.net/n9rla> List Administrator for: InHam+grid-loc+ham-books
Ask me how to join the Indiana Ham Mailing list!

 
Your First HF Dipole  
by K9ZF on June 19, 2010 Mail this to a friend!
Here is my extra tip:

When tape wrapping the connectors, put the first layer of the tape on up side down [sticky side up]. Then cover this with several good tight layers sticky side down. This keeps the tape adhesive off the connector and makes it easy to reuse when the time comes.


After taping the connectors, I cover this with a good coating of coax seal. The coax seal does a good job of keeping the moisture out, and the tape keeps the coax seal out of the connector. Yes, this might be over kill, but it works for me.


73
Dan
--
Amateur Radio Emergency Service, Clark County Indiana. EM78el
K9ZF /R no budget Rover ***QRP-l #1269 Check out the Rover Resource Page at:
<http://www.qsl.net/n9rla> List Administrator for: InHam+grid-loc+ham-books
Ask me how to join the Indiana Ham Mailing list!

 
RE: Your First HF Dipole  
by AE5JU on June 20, 2010 Mail this to a friend!
I did a short "how to" on this, with pictures and everything. ;-)

http://k9zw.wordpress.com/2010/05/12/guest-post-weatherproofing-antenna-coax-by-paul-ae5ju/

73
Paul - AE5JU
 
RE: Your First HF Dipole  
by AE5JU on June 20, 2010 Mail this to a friend!
I did a short "how to" on this, with pictures and everything. ;-)

http://k9zw.wordpress.com/2010/05/12/guest-post-weatherproofing-antenna-coax-by-paul-ae5ju/

73
Paul - AE5JU
 
RE: Your First HF Dipole  
by W1DLB on June 21, 2010 Mail this to a friend!
Funny...sort of.

Amazed you think they are NOT.
Use mine on 20m and 75/80m and work the world and country respectively w/o problem.
Try one You might like it.
They are not the most commonly used antenna for no reason.
 
RE: Your First HF Dipole  
by N1LO on June 21, 2010 Mail this to a friend!
Very nice article, with a lot of good follow-up comments.

If you can suspend the feedpoint, you can use very low tension in the legs for long life.

I must point out that if you can't suspend the feed point, a pulley and counterweight on one end is an extremely effective way to control sag, whipping, and breakage! It's also makes it much easier to raise and lower the antenna for tuning and maintenance without abrading the line in the trees.

Here is an excellent pulley: The Everlast unit, on the rope aisle at Lowe's. It has about a 3" diameter roller and is very tightly shrouded to prevent line jump. It's all nylon with a bronze axle, and is very free running. With a topcoat of 'Fusion' (made for plastic) paint to intercept UV, these give years of trouble free life.

String trimmer line works nicely instead of rope. I use the 0.105" "titanium" line. No end insulators needed. For terminations in the trimmer line, use the double sleeve crimp ferrules sold for fishing or wire rope.

UV will eventually degrade it, but it's cheap to replace, especially if you use a complete loop over or through your tree, like a flagpole halyard.

I also use a loop of trimmer line as a center insulator.

Regards,

--∑∑∑ MARK∑N1LO ∑∑∑--
 
RE: Your First HF Dipole  
by DO1KEY on June 22, 2010 Mail this to a friend!
I have to say it also - GREAT article. It helps me as a new-born OM to get on air soon, I hope...

73 de DO1KEY
 
Your First HF Dipole  
by K3ROJ on June 24, 2010 Mail this to a friend!
Just coming out of the Army in 1962 after being extended for 6 months because President Kennedy tried to have Castro assassinated, I needed to install dipoles for 40 and 80 meters at my Mothers house. The way I always remembered the number to figure out the length of each leg of a dipole is remembering the chant when marching, "hut 2, 3, 4" so that 234/7 = 33.4 feet or 33ft 5 inches.
 
RE: Your First HF Dipole  
by K7LRB on June 25, 2010 Mail this to a friend!
Beats me what happened to my earlier post. I clicked just ONCE, I really did! Oh well.

73,
de Larry
 
RE: Your First HF Dipole  
by N3JJB on June 26, 2010 Mail this to a friend!
Great article.
For all those that have or are considering a g5rv, google ZS6BKW. You'll never go back.
 
Your First HF Dipole  
by KD0MBL on June 30, 2010 Mail this to a friend!
I'm a noob and really appreciate all of this info for those like me.

Now if I could just decide on a radio(s)! :)
 
RE: Your First HF Dipole  
by AE7VT on July 3, 2010 Mail this to a friend!
The WD-1T wire is military grade field telephone wire. It has and extremely tough jacket similar to what the telephone company used for outdoor service drops from telephone poles. Then, the wire itself has several strands of steel with the copper which is what gives it all it's strength. An antenna made with this wire can be installed and used for many years especially if the joints are coated with a sealer or shrink-wrapped with thick-wall tubing. Then, the actual connection to the coaxial, depending on what you use, can be wrapped with 3M #88 weatherproof electrical tape to seal out moisture. Be sure to wrap from the bottom up so rain water drips off easily.

Good article and good basic information to remember.

73, Paul - K7IN
 
RE: Your First HF Dipole  
by NO6L on July 7, 2010 Mail this to a friend!
I'm still amazed that people still think a G5RV is multiband, *by design*.

Louis Varney, G5RV himself said that his antenna was not *designed* as multibanded. It just happens to be able to be easily tuned on most bands other than 20M, with a tuner. I'll take a fan dipole or doublet operated as a harmonic antenna any day over a G5RV.
 
Your First HF Dipole  
by W5XJ on July 11, 2010 Mail this to a friend!
Phil that was an excellent article. I wish I had seen it back in June 2009 when I got my general class ticket and promptly bought my first, and last, G5RV antenna at Hamcom. Talk about RFI, i tried using an air balun and learned about baluns and RFI the hard way. Thanks for "giving back" to the hobby/service. They ought to put your article in the Gordon West and ARRL license study books - Gordo / W1AW think about it!

73 de KE5ZYP
Grant
 
Your First HF Dipole  
by GW0NSR on July 23, 2010 Mail this to a friend!
Just to say that this is a very readable article, with much sound basic advice. Have used coax fed dipoles for many years and never had much of a problem with them. Bear in mind, though, that if you substitute 300 or 450 ohm flat twin feeder, or even 600 ohm ladder line, the losses experienced with coax will be substantially reduced. Worth remembering for the next dipole!! You will, however, require an antenna matching device, such as a transmatch. Good luck to all newcomers to the hobby and I hope it gives you as much pleasure as it has given me over the last fifty-odd years. 73's to all. Tony Tuite in North Wales.
 
Your First HF Dipole  
by A22EW on July 26, 2010 Mail this to a friend!
this brings back good memories of 1994 when my first dipole for 40m went up.

Here is some tips:
1. Use regular insulated wire vs thicker gauge uninsulated wire. you only add to weight and not to performance.
2. Do NOT cut the tips of the wire to tune. Instead, fold the tip on to itself and tape it down. This will avoid you ever over cutting.
3. If you are that obsessed with having insulators at the end of the dipoles, use a plastic coke/pepsi 2l bottle tops; v-cut 2 holes on each side at the top of the lid. I can attest that a. it works over several year periods b. It will bring sheer laughter to any visiting ham to this interesting approach.
4. Balun is not a must; if need just make up a open air balun on a 1.5" pipe vs getting a commercial.

The dipole was with me many years but i progressed to more interesting experiments with delta loops.
 
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