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
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.
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
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