HORIZONTAL LOOP ANTENNA CONSTRUCTION
The Horizontal Loop, also known as the LoopSkywire Antenna, is an old but very effective design. Although this design has been around for a long time, it is only gaining in popularity now due to the recent improvement in high power antenna tuners. The main purpose of constructing this omni directional antenna is to provide a multi band antenna which performs well from the lowest frequency band for which it is designed, all the way through 10 meters. It will usually even work well on 6 meters if your tuner and balun will handle that band.It must be understood that an antenna tuner (trans match) will be necessary for use as a multi - bander, as well as the use of twinlead feed line. I recommend 450 ohm ladder (window) line as the feedline. (See bottom of this page for types of twin lead available). You will of course need a balun near your tuner, ( I recommend a4:1 Current Balun ), or a tuner with a built in Balun, to feed your rig’s unbalanced antenna connector. I use the MFJ-912 (W9INN) Balun. It is a Voltage Balun, but is of good design, and works well.
How long to make it.To cut the antenna wire length to resonance we use the formula: Length (in feet) = 1005 divided by frequency (in MHz). We must subtract 4% of the total full wave length if we are using insulated wire. Example : For a 160 meter loop, 1005 divided by 1.800 (lowest 160 meter frequency inMHz) = 558 feet. If using insulated wire, shorten the overall length by 4% (-22 feet). 558 feet minus 22 feet = 536 feet. This is due to the slightly decreased velocity factor of insulated wire. The length of the feed line (450 ohm ladder line) may require some final adjustment or it may become part of the loop and serve as a radiator. My loop is 520 feet of insulated wire with a 28 foot lead in, and is resonant slightly below the bottom of the 160 meter band. I intend to shorten the insulated wire to exactly 508 feet the first time I take it down for any maintenance (Which may be a long time). You do not need to get it that close to resonance on the lowest band, but for usanal retentive types it is an interesting distraction. Use this handy WireAntenna Calculator (Courtesy of CentralCalifornia DX Club) for all wire antennas.
Tuning.This design is a full wave (or longer) at the lowest frequency for which it is intended. It need not be cut to resonant length even for the lowest frequency band intended. It can be cut longer, even much longer, letting your tuner handle the mismatch. The most practical design however is to cut it to resonance at the lowest frequency of the lowest band targeted as outlined above. With some adjustment of the length of the feed line, you may find several bands or portions there of which will be resonant enough to allow you to bypass the tuner. If using a separate balun to feed your tuner, try to keep the connecting coax as short as possible. 10 to 15 feet or less should not be a problem.
How High. Ideally, this antenna should be hung as high as possible, but even at very low height (as low as 10 to 20 feet above the ground) it can be very effective. Be sure to hang it high enough that it cannot be contacted by anyone on the ground. It can be hung beneath the canopy of the trees as long as the wire does not touch any leaves, branches etc.Note: If insulated wire is used, contact with leaves or branches is permissible, but is best avoided to prevent the insulation from eventually being damaged.
What if I don't have room for a 160 meter loop? Make the loop as large as your property will allow. If you can cut it for 160 meters go for it. If not, go for 80 meters or 40 meters. A 40 meter loop requires less than 130 linear feet of insulated wire. That is a square of only 33 feet per side. Nearly any suburban residential lot should be able to accommodate that size. Remember the sides need not all be equal, it can be almost any shape that encloses the largest area possible. EXPERIMENT !
At first blush, this design may appear to be just a big short circuit because each leg of the feed line is connected to the end of a big loop of wire. True, it is a short circuit at D.C. but at Radio Frequency, which is A.C., it is an excellent radiator. Do not be misled by reports (mostly from those who have never tried it) that this is only a vertical radiator or “cloud warmer” design. When used with ladder line you will be impressed with its performance as a transmitter antenna and surprised at how quiet it is as a receiving antenna. Naturally though, performance will increase some what with height above ground.
I strongly suggest the use of 12 gauge stranded, insulated, copper wire, which can be purchased at HomeDepot and other home improvement centers for about $ 40 for a 520 foot roll. That is enough to make a 160 meter loop. The loop should be hung as high as is practical, and should be in the approximante shape of a big circle or square. It need not be perfectly horizontal,and the shape can really be a big square, or rectangle or any multisided shape, so long as the two ends meet at convenient point where an insulator can be used to attach the feed line. The most critical element is that the loop should encircle the largest AREA possible. A circle, or square, or rectangle, is much better than anelongated oval, or triangle, or dog bone shape. My 160 meterloop is 7 sided, with none of the legs of equal length or height, and it is a stellar performer. It is 25 feet above ground at the highestpoint, and 15 feet at the lowest. Mine is 520 feet in total length.
The loop can be attached to poles, trees, buildings etc., whatever is convenient. It is best of course to try to avoid running it with a leg parallel to nearby power lines. NEVER INSTALL ANY PORTION OF THE LOOP OR FEEDER LINE ABOVE OR BELOW A POWERLINE! The loop can be freefloating (that is attached so that it can be pulled tight at the two ends and just looped through the guy lines that hold it up) or it can be firmly attached at one or more points as necessary. I use heavy(5/16 in.) black Dacron rope with a knot that is loosely tied to the wire. Mine is free floating so that if I disconnect the center insulator, the entire loop will go slack, but will still be loosely attached to the guy ropes. This is probably the best way to hang it,especially if it is attached to trees, as it allows for some movement as the trees sway, and does not stress the wire. If it is left freefloating or partially so, it is a good idea to leave a little slack in the wire. There is no reason to stretch the wire guitarstring taut. Unless you are using a high power amplifier in a verywet environment, it is not really necessary to use insulators to attach the Dacron guy ropes to the wire when using insulated wire, as the Dacron rope does not tend to absorb much moisture. I highly recommend the use of Dacron rope due to its strength and resistance to deterioration from sunlight and the weather. This rope can be purchased from most ham radio stores and is available from MFJ,HRO,DXEngineering and AES. Note: This maybe called Dacron, Dacron/polyester or Dacron/nylon rope, or just polyester antenna rope, and should not be confused with Dacron wire rope, which has wire woven into it, and is sometimes used as an antenna wire. It is unlikely that you will find Dacron rope at a local hardware or home improvement store. Whatever type insulator you choose as the attachment of the two ends of the wire to the lead in, be sure to solder the antenna to the lead in wires well. I use apiece of PVC pipe as the insulator. The antenna can be fed at ANY point. I chose to feed it near the end of one leg for convenience. The feed line should be at an angle to the antenna wire, a 90 degree angle if possible to prevent coupling of the feedline to the antenna wire.
I want to stress the importance of several points:
Remember, each end of the wire loop attaches to one of the legs of the lead in wire.
The higher above ground you can hang your antenna the better.
Enclose the largest area possible. This is the key to great performance.
For best long term results, I recommend the use of #12 insulated stranded copper wire. The best color is black, as it is sunlight resistant and less visible. This wire is also quite strong and flexible, and the insulation reduces precipitation static.
Use black Dacron rope (Not Dacron wirerope), to tie it up. Just about any other rope will rot away in ayear or so. NEVER use metal wire or wire rope as it will interact with the antenna and screw things up royally. If you choose not to use Dacron rope, I suggest using heavy, non - metallic Trot Line Cord which can be found at sporting goods stores, or in catalog scatering to cat fishing enthusiasts. It is strong and rot resistant but will not last nearly as long as Dacron rope.
For best results, I recommend that you do not try to use it at a frequency lower than the lowest resonant frequency. (Don’t try to load an 80 meterloop on 160 meters) It will perform well at higher frequencies with a tuner. If you experiment with loading it on a lower than resonant frequency, try it at very low power while attempting to adjust your tuner for minimum SWR.
Do not feed It with coax. This is a MULTI bandantenna, and 450 ohm ladder line will have very little loss at non resonant frequencies. Ladder line is not that difficult to deal with. You can cut a slit in your attic etc. to feed the line in. Just keep it 3 or 4 inches from any metal and don't bend it in a radius tighter than 10 or 12 inches. You can run it to a 4:1 Balun under your eaves for example, and then run a short length of coax into your shack. Experiment a bit and see what works best for you. 600 ohm open wire line will also work well, but is not as readily available, nor as easy to work with as the insulated 450 ohm window line.
If you have trouble getting it to tune to minimum SWR on any band or experience RF in the shack, try lengthening or shortening your ladder lead in line. In a worst case scenario, it maybe necessary to change the position of the feed point. Some bands may exhibit lowest SWR when the tuner is bypassed. Experiment as necessary. If using a manual tuner, draw up table of the necessary tuner settings at various frequencies, for quick reference when tuning.
A word of caution: These big loop antennas are a large target for a lightning strike, either a director nearby hit. They can also build up a significant static charge from precipitation or dust in the atmosphere. It is crucial to disconnect the lead in, and ground it ( direct to ground outside the shack ) if possible, before an electrical storm approaches. To prevent equipment damage from static charge buildup, always ground both leads of the window line, (or center wire and braid if using acoax run to your tuner) momentarily, before connecting the feed line to your tuner or an antenna analyzer.
Types Of Twin Lead
300 Ohm Twin Lead
450 Ohm Window Line
True Ladder Line - Normally 600 Ohm
Also Called TV Lead In
Also Called Ladder Line
Also Called Open Wire Line
Frequently Asked Questions
Q. Why do you recommend a 4:1 balun when using 450 ohm or 600 ohm feed line?
A. The 4:1 balun is readily available, and offers the best overall compromise for a multipleband loop antenna. It will normally provide an impedance which your tuner can work with at all frequencies for which your antenna is designed. Remember that the impedance listed for feed line in only its characteristic impedance. The actual impedance varies with the frequency of the signal. A 1:1 balun will probably work with most antenna systems.
Q.Which is best, a voltage balun or current balun ?
A. A current balun has some advantages regarding efficiency and core saturation issues. A good voltage balun, rated for the power you intend to run will work quite well in most circumstances. I recommend using a voltage balun if you already have one. If you are buying a new one, a current balun will be a slightly better choice in the long run.
Q. Why do you recommend the 450 ohm window line instead of open wire or 300 ohm TV twin lead ?
A. Even though it has slightly more loss, the ladder line is easier to work with, and more readily available than true open wire line. The TV twin lead has too much loss, and will not handle very much power.
Q. How long should my feedline be ?
A. Longenough to reach your tuner or balun, plus a few additional feet for trimming.
Good lengths(in feet): Somewhere around 40, 80, 110, etc.
Lengths to avoid (in feet): 32, 65, 96, 130, and 260- and multiples of any of those. If in doubt, consult the ARRLAntenna Book.
Having said that, I recommend that you simply make it a bit longer than necessary, as previously stated. Then, if it won't tune on a certain part of a band or bands, or if you experience RF in the shack, shorten the feedline a foot or so at a time until you hit the sweet spot and overcome the problem. An antenna analyzer will be of great value here. Although it is easier to cut the line to shorten it, all twin lead can be lengthened by splicing. Just do a good soldering job, and seal the splice with epoxy or liquid electrical tape.
Q. What should Ido with the extra length of twin lead if I hit the sweet spot and don't want to shorten it ?
A. Run it back and forth in a zig-zag pattern, or in large loose coils away from any conducting material. Do not coil or roll it back up on itself.
Q. Can I make an attic loop antenna, or aloop around the perimeter of my roof ?
A. You sure can, and in this era of CC & Rantenna restrictions, it may be your only choice. Of course it will not work as well as one up clear and high in the air, but you will probably be surprised at how well it works. It will be better than almost any other stealth type antenna, if you have room for it. Try to keep the antenna wire a few inches off the roof by short PVC or wooden standoffs, or hang it under the eaves. Naturally, as with any other near house antenna, you may experience some RFI issues both to and from household wiring and appliances, but IF you have such problems, they can normally be cured by the judicious use of chokes and toroids. The ARRL RFI Book is an excellent reference on how to avoid and cure such potential problems.
Q.Can you help me understand why twin lead is a much better choice than coax for feed line on multi band or other non resonant antennas ? Doesn't the tuner transform the impedance to 50 ohms and bring the SWR down just as well with coax ?
A. When you are using coaxial cable under high (greater than 3:1) SWR conditions, the tuner may provide the 50 ohm match t to your radio, but the mismatch and HIGH SWR still exists between the antenna tuner and the antenna! This translates to very high losses in the coaxial cable. At HF frequencies, the loss in ladder line is so low, you can still see good results even when the SWR is horrendous. The antenna tuner provides the 50 ohm match to your radio, and you really don’t care what the SWR is between the tuner and the antenna, due to the inherent low loss of twin lead.
Q. Will the built in autotuner in my transceiver be sufficient for use on a multi band loop antenna ?
A. Unfortunately it probably will not. Those tuners are only capable of handling a mismatch of about 3:1 or so. You will be encountering much higher ratios than that, hence the need for a good stand alone tuner. Most manual and automatic tuners on the market today will do a good job, as long as they are capable of handling the power levels you will be running (in the future as well as when starting out).
Q. I already have ahorizontal loop fed with coax. I am able to obtain a low SWR reading on all the bands at and above the fundamental frequency, using my stand alone tuner, but the antenna does not seem to perform well on several bands. How can I determine which bands will most improve by changing to twin lead ?
A. With your tuner bypassed, use either an antenna analyzer, or your radio’s SWR meter, and measure the SWR at various points throughout the 80 to 10 meter bands. Those frequencies where you have SWR of about 3:1 or higher are the spots where you will most benefit from the use of twin lead.
Bear in mind that when your tuner is used, SWR indications can be adjusted to near 1:1 on most bands, even using coax as your lead in. That is because you are only measuring the SWR between tuner and radio. That will keep your modern solid state radio happy seeing about 50 ohms, so it will produce full power without folding back power to protect your finals. However, when using coax on the non resonant frequencies, most of that power is not radiated, since it is simply wasted heating up your coax.
When you change to using twin lead, most of that same power will not be wasted, but will radiate from your antenna due to the inherently low loss of twinlead, even at non resonant frequencies. The Standing Wave will still actually be present on your twin lead, but it does not matter since it will make it to your antenna where it will radiate. You won’t see the difference on your power meter or SWR meter, but you will be putting out a much stronger signal, and should get good signal reports. You will also notice a marked improvement on received signals.
As a reminder, if you have trouble getting good SWR readings on some frequencies, experiment by slightly changing the length of your twin lead, or in severe cases even relocating the feed point.
Q. How much power do I actually lose with coax VS twin lead ?
A. Assume that you have a 100-W transceiver connected to one of the transmission lines listed below. How much power (in watts)
actually makes it to your antenna ? Examples are shown for 80, 10 and 2 meters, with 100 feet of transmission line and SWRs of 1:1
and 6:1 oneach of these bands. Remember that SWR can easily exceed 10:1, and is often even much higher, on a non resonant (multi band)antenna.
It’s worth noting that ladder line exhibits substantially less loss on the HF bands than just about any other transmission line available. This means you can get away with SWRs on ladder line that would cause intolerable loss with coax.
The object of any antenna system is to get RF into the antenna, and out on the air. Your transmission line plays a critical role in getting this job done. When you shortchange yourself on transmission line, you shortchange your whole station. As long as an antenna tuner is used, ladder line offers some compelling advantages compared with coaxial cable in almost any medium- or high-frequency application. This is particularly true when you want multiband operation with a single antenna.
Q.Is the increased performance of a twin lead fed, multi bandantenna really worth the effort VS coax fed ?
A. See the excerpt below, from "Understanding SWR By Example"by Darrin Walraven, as published in the November 2006 issue of QSTMagazine, and judge for yourself.
Good luck with your project. Chances are you will be so pleased with this antenna that you will no longer use any other wire antenna at or above the resonant range of your Horizontal Loop. Enjoy! Thanks to Randy Davis/K5RCD for the use of this information. Visit his site as well: www.k5rcd.org
BUILD THIS MULTIBAND FAN DIPOLE
FOR ALL BAND HF ANTENNA EXCITEMENT
Here is a fairly simple and easy to build multi band horizontal fan type
dipole that can be constructed for all band operation from 160 meters up
thru 6 meters or even higher.
In the drawing above, it is shown for just four bands, 80 thru 10. One
separate dipole for each band needed. However you can build it to suit
your own preferences by using the standard formula for a dipole:
468/freq mhz = total length for each band. Use the formula for your
desired center frequency.
Each dipole length above in RED is in feet and tenths of a foot for the
center of the General portion of each band and is derived from the
above formula and should be cut longer for swr trimming. USE #12 TO
#14 GAUGE COPPERWELD WIRE IF POSSIBLE or use what you
have on hand. The top most dipole must support the entire weight of the
Start with your lowest (in frequency) band of operation as the main (top)
support for the entire setup. Cut it per the formula but add a couple of
feet on each end for tuning. Try to use a wire size that will support the
This is the main support for all the other dipoles and must carry their
Cut a dipole for each band of operation.
Cut each full length in half....example: for the 10 meter length from the
formula you get 16.1 feet for the total length. Cut it in half at about 8 feet
per side. Make sure you cut each length about a foot or more longer for
swr trimming and attaching to center and end insulators!
If you are building the four band dipole above, you should have 8
lengths of wire scattered all over your work area.
WARNING! DON'T DO IT IN YOUR LIVING ROOM, THE XYL WILL
NOT BE VERY HAPPY WITH YOU AND AFTER SHE GETS
FINISHED WITH THE QRM,,,, ALL YOUR ANTENNA BUILDING WILL
HAVE TO BE DONE FROM THE DOG'S HAM SHACK!
It is assumed that you have your end support poles, trees, center and
end insulators, pulleys all ready to go before you start working on the
A very important part of this design is the installation of the pulleys (in
yellow on drawing) on each end attached to each side support.
They are added to this design due to the swr trimming process and
make it very easy to pull the entire antenna up and down while making
the swr adjustments. Mount a suitable size pulley on each end attached
to your pole, trees, etc for the diameter of cord or rope used to support
Start your antenna trimming with the top dipole.... attach your coax to
the center insulator leaving several inches of the center conductor and
shield exposed. Each half of each dipole will be connected to the coax
center pigtail and the shield separately. In other words, connect one
side of the dipole to the center conductor and the other side to the
Attach the other end of each half of the longest wire to the support cord
and run thru the pulley on each end and pull the dipole up into the air
between the end supports. Check swr.
Trim as needed with low power for lowest swr possible, lower with
pulleys, attach the next highest band dipole electrically to the same
point as the first dipole, raise it to operating height, check swr, lower for
trimming, up and down, up and down.........due the same for all other
dipoles for each higher band of operation.
When you are finished with the highest band of operation, pull the entire
system up with the pulleys and tie of at the bottom securely.
Make certain that the coax center conductor is attached to one half of
each dipole and the shield to the other half. All dipole ends at center
insulator are connected together.
This may not be very clear to the new antenna builder so please see the
drawing below for the center insulator arrangement.
The white areas in the center support drawing above are mechanical
supports, clamps, wire ties or whatever your genius can come up with to
support the main (top wire) and the weight of the coax.
Remember, all the weight of this antenna system is supported by the
The connections should be soldered and all should be sealed including
coax end from water, ice, snow etc.
Use a 1:1 balun like the "Ugly Balun" project page on this site close to
the center before coax goes to your rig.
For best performance get it as high as possible and remember that
since this is a dipole arrangement, it will be somewhat bi-directional
towards and away from you as viewed in the drawing. (BROADSIDE)
Remember that all elements will interact with each other in the tuning
process and the final setup must be secured so the angle or distance
between each dipole does not change when blowing in the wind, etc.
The angle or distance between each dipole is not critical but the final
spacing must be maintained!
It will take lots of work (trial and error) in getting each dipole to the
lowest SWR. Just keep TRYING.
It should also be noted that the antenna can be used in an inverted v
fashion but remember the spacing should be secure in the final
operating position. Tune it as in all the above instructions. You may use
a tuner with this antenna un-trimmed to save a lot of work!
EXPERIMENT! EXPERIMENT! EXPERIMENT!
The multiband fan dipole can be very difficult to tune for lowest swr in
some installations. There are many variables that will make tuning
difficult. Height above ground, sometimes the angle of each dipole
relative to the other dipoles, surroundings , etc. If you can get the swr to
around 2 to 1 or lower for each band....don't worry too much about it.
You might also consider using a good antenna tuner if you are having
major tuning problems. A 2:1 SWR can be handled by most radios.
You might also consider removing HF combinations such as 40/15
meters and 80/30 meters.
For these cases, cut the element for the lower frequency and let it serve
double duty at the odd harmonic. In other words, cut the 40 meter
element and let it serve also as the 15 meter element which eliminates
the 15 meter section.
Make sure that the distance between all dipole elements does not
change when tuning.
They must be in a fixed position always with some sort of spacer. In
theory, we could fashion a four-wire antenna for the 80, 40, 30, 20, 15
and 10-meter bands.
In practice, it may be difficult to obtain a good match on all bands.
Since the resonant length of a given element in the presence of the
others is not the same as a dipole by itself, tuning can be a tedious and
difficult procedure. Adjust elements for resonance in order from lowest
frequency to the highest such as in an 80 40 20 10 combo.....start with
80 first.....then go to next higher frequency dipole.
Always cut each dipole a lot longer than required for each band to make
Trim as needed for your operating frequency.
All of these bandwidth, adjustment and matching problems are easily
solved with an antenna tuner at the transmitter, feeding the antenna
through 100 feet or less of RG-8 coax.
Good luck and have fun!