Kg3v Ham Radio Blog

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Loop-on-Ground, the simplest Receive-Antenna you will ever Build, and it
Works

Posted: 04 Jan 2020 07:38 AM PST
https://kg3v.com/2020/01/04/loop-on-...-and-it-works/


I have been experimenting with some Receive-antennas for the Low bands (80
and 160 meters is low-band to me). I discovered these popular antenna from
other Hams at the Contesting Club I belong to. Nearly all the serious
Contesters at the Potomac Valley Radio Club (PVRC)and all of their
Superstations use Receive Antenna.

Receive-Antennas typically provide relatively low signal levels, but also
very low Noise levels. So once you amplify the small received signals, you
can receive signals with very low noise. There are many different types of
Receive-Antennas and I would suggest something like the ARRL Antenna Book
for details.
My Initial Trials with Receive Antennas

My current operating QTH is on ~ 0.9 acres, but it is narrow. So I do not
have huge straight runs for long antennas. The natural first choice for
Receive-Antennas seemed to be the Beverage antenna. for 160 meters, these
ideally need to be well over 400 in length. That was never happening at
this location. I discovered something called a Beverage-on-ground or BOG
antenna. Putting a Beverage antenna on the ground, theoretically allows the
use of a much shorter antenna. I had about 200 to work with, and gave that
a try on 160 meters. I did not have much luck with that, although I must
admit I only tried for a couple weeks to get it tuned and working. So I put
one Beverage at about 7 height, but it is only 200 long. It helps in some
situations, more on 80 or 40 meters. but does not exhibit the desired
directivity at 160 meters.
The Loop-on-ground (LOG) Antenna

Doing some reading, I discovered an article about a so-called
Loop-on-ground (LOG) antenna. I found this great article by KK5JY about the
Loop-on-ground antenna online. I had heard of this antenna before, but with
my failed BOG experiences I was skeptical and never tried one. About this
time, I saw an email from a friend (Steve, K3KQ) on theÂ* Club email
reflector of the Fauquier Amatuer Radio Assoc (FARA). He was working with
some other local Hams that were interested in the LF/VLF Bands and telling
them they really should try a LOG antenna. Time to give it a try.

There was a 160 meter CW contest in a couple days that I wanted to work,
but I currently had no antennas for that Band. I threw a dipole in the
trees at about 25, and planned to try a LOG for help with Receiving
signals. The LOG is simply a loop of any shape, but I was going to use a
square. The article says that a square with 15 of length on each of the 4
sides will work on 160 meters. You do not need ANY Ground system, no rods,
no radials, nothing, according to what I have heard. Of course, you still
want to provide a safety-ground at the entrance to your Shack. When the
antenna is built, you just put it on the ground and attach a feedline.
Almost TOO easy.
Construction of the LOG Antenna

BEsides the wire, the other components needed for this antenna are an
impedance transformer (~ 5:1 turns ratio), a couple common-mode chokes, and
some RG-6 or other 75-ohm feedline. The transformer can be wound on a
toroidal or binocular core. The core needs to use a ferrite material that
is suitable for these low frequencies. Since I had tried some Beverages, I
had plenty of Type 31 ferrite material around, including a large binocular
core. Several other Types are useable, and may be desired if you hope to
use this antenna for LF/VLF work. I did not plan to do that in the
foreseeable future.
160-meter Loop-on-ground Antenna Results

I connected it all up and hooked the feedline (about 150 of RG-6) to my
rig. I chose to use an outboard low-noise 160-meter preamp (KD9SV design,
purchased from DX Engineering) that I have, but most modern radios also can
provide the needed amplification. This preamp was made for BOG antennas,
and there are several other models that should also work. By the way, KD9SV
is very helpful if you should run into any trouble with his products. I
discovered this when I accidentally reverse-powered my preamp and it needed
repair (yeah stuff happens..). The preamps in my FTDX-3000 seemed to be
suitable, and you may find that the preamps in your Radio are also
sufficient.

The initial results were encouraging. The signals on 160 meters were indeed
weak, but the noise was relatively low. Once I enabled the preamp. I had
plenty of signal to work with. The FTDX-3000 already has a very low-noise
level on receive. Listening to the 160-meter Band with this setup was very
enjoyable. My only antenna to compare with was my low-hanging dipole. I
must admit that I could hear every signal on both antennas. But the level
of noise was much worse on the dipole. This little loop made the difference
between listening pleasure and a painful Contest with high noise-levels.
Conditions just happened to be so good, that I had a good Contest run
(about 215 QSOS in 4.5 hours) and even some EU stations responding to my
CQs. I only listened to the dipole for periodic comparisons.

If you are struggling to get a good Receive-antenna for 160 meters, I
highly recommend this Loop-onGround design. Your mileage may vary, but I
would be surprised if you do not have a favorable result, and you will
never build or install a simpler antenna that the LOG.

I may try some enhancements, or even using multiple loops to get some
directionality. But fo rnow, this loop will be a standard part of my
station for any 160 meter operating. I have heard it may also be useful on
80 and possibly 40 meters. I hope to find out soon.