Full Wave Horizontal Loop Antenna
or, Why I use an Electric Fence on 160 Meters
    

A dipole antenna just will not work unless it is at a sufficient height. The multiband dipole I describe in another article could have another wire added for 160 Meters. But the repeating resonances at 2 Mc intervals would have detracted from its performance. Even if you managed to get it to ¼ wave up at 160 Meters, about 70 feet, it would be problematic. The extended G5RV and other flat tops are just dipoles with a different feed method. For that matter, the off center fed types like the Carolina Windom are the same stuff. End fed long wires must be hung at similar height to get the performance to be heard well. 120 feet or more is required for long haul work.

A vertical would be a mechanical monster, and cost a fortune. Or the loading coil would reduce bandwidth and radiated signal. I did a helically wound 160 Meter vertical about 25 feet tall, but it was like erecting a wet spaghetti noodle. And it was mounted over a ground screen which used up two ¼ mile rolls of electric fence wire. It did work for DX, but was lousy for local ragchews beyond ground wave distance. At high noon, I was able to talk direct to Long Island with 100 Watts during the summer to another station using a similar vertical on ground wave.

You hate to climb trees. And you have no tower, but want to work short haul on 160.

The theoretical length for a full wave loop is:  
  Circumference (in Feet) = 1004 / Frequency (in Megacycles)  

This works out to a total length of wire of 500 Feet. This is available as a spool of #12 or #14 THHN wire at Lowe's for less than $50. Use black insulation for stealth. The wire will not cut to formula length with insulation, but it is a starting point.

The insulators are available at Agway or a farm store. They are electric fence insulators. Cheap plastic insulators work just fine, since the loop is a low impedance device.

For heights of 20 Feet, a loop will outperform a dipole or anything else at the same height. In fact, it KICKS A** by comparison. Under good band conditions, I have worked the west coast of the USA with 100 Watts presumably on multihop. I think I might be able to do europe this winter. But it is NOT a vertical over a good ground for DX, so don't count on it.

IMPORTANT: DO NOT WASTE MONEY AND RF ON A BALUN FOR THIS ANTENNA. The tuner takes care of it.

My electric fence antenna runs from tree to tree in a rectangle 100 feet by 125 feet. No coax is used. One side of the antenna goes directly to a ground stake, for lightning protection. A ground wire to the pass through panel in the double hung window by MFJ completes one side of the loop. The other side goes to the center of a coax connector on the panel. Impedance is about 150 ohms. That connects via a short piece of coax inside the house to my antenna switch and tuner.

For low heights, a 75 meter loop also is a good choice, if you cannot erect a higher dipole. I took down my 75 meter loop to make room for the high dipole described in my other article. As a plus, it will keep your giraffe herd safe at home.

Update 8/23/2014: HOW TO FEED A LOOP

On Long Island, I am able to bring the wire directly into the shack and feed it from the Dentron MT2000. I do NOT use the internal balun to avoid losses inherent in such operation. I ground one side of the loop. I feed the other wire of the loop from the coax connector. Balance does not matter. Getting the most RF in the air matters. Only use a balun when it is indicated. Some guy telling you that you oughta have a balun is not an indication.

In Ithaca, I have to run over 100 feet of coax to get the loop away from the power lines to get quiet reception. This introduced a lot of loss. I got rid of all that loss. Nope, no open wire line. Yes, the open wire line has less loss in dry weather. Not so much in wet weather. The mechanical hassles and costs are substantial. And the balun is lossy. Why save a couple dB in feedline and throw it away in a balun and lossy antenna tuner?

There is a better way. Use a quarter wave matching section. Order up some 70 Ohm coax from DX Engineering. Put a connector on one end of about a quarter wave of the coax. Using a MFJ259B, shorten the open end till you get zero reactance and a zero resistive component at 1900 KC. Then install the other connector. This works out to around 100 feet, accounting for the velocity factor of the coax. The actual length of the coax is shorter than the calculated wavelength because the wave travels slower in the coax than it does in free space. This got me to a point near the house where I could transition to 50 ohm coax. I installed a grounding stake and some lightning grounding from DX Engineering before I brought it in the house. See the picture for details.

I used a standard TV mast to support the feed line. Balun??? We don't need no @#$% balun! RF going somewhere is better than heat going nowhere.

I will furnish some minor math to make your head hurt later. But here are the pictures.

   
  

73,
Janis
AB2RA
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