Testing the Loop-on-Ground with Real Signals
In a recent RTTY contest
, I watched as a friend did
a CQ run on 40m
. He was using a full-size 33' 40m vertical at his station, which
has similar ground elevation to mine. Since our stations are also within a few miles of
each other, this allowed me to watch him work several stations in quick succession, while
I observed his run on the LoG antenna. In order to compare the receive performance
of the two, I watched to see how many stations he could hear on the vertical that I could
not hear on the LoG, and vice versa
The vast majority of stations that he worked were also perfectly copied on the LoG.
There was one station that he heard that was marginal copy on the LoG. Surprisingly,
there were several stations that I could copy perfectly on the LoG that he never heard on
his vertical. He called CQ, and they answered him, but he just couldn't hear them.
I looked up those stations to find their location, and none
of them were inside
the skip zone, or anywhere near it. In fact, the stations he was missing were all
on the order of 1,000 to 1,500 miles away from him. Because of the pattern differences
at high angles, you would expect the LoG to hear close-in stations better than the vertical,
but these were not
These were low-angle skywave signals that the LoG simply heard better than the vertical.
So at least for this one test, the 15' square LoG antenna actually pulled in more stations on
receive than his full-size vertical antenna on 40m. When we both switched to 80m, I was
able to copy several stations, while he couldn't hear anybody.
More recently, I used the 15' square loop-on-ground as a dedicated receive antenna for the
ARRL 160m Contest
. The antenna was
pointed roughly ENE/WSW. I used a much larger vertical loop antenna as the dedicated
transmit antenna for the event, similarly oriented to the compass, and separated from the
LoG by roughly 50' to the broadside. Bear in mind that I live near the center
of a town of roughly 50,000 people, and my lot is approximately 100' by 60', located in a
subdivision of similarly-spaced houses. A resonant vertical is unusable as a 160m
receive antenna here, for obvious reasons. If the RF surroundings weren't already
busy enough, the weekend of the contest was filled with an active weather pattern, with
nearby storms and showers during the entire event.
Despite these challenges, the LoG antenna performed beautifully. The recieved S/N
ratio on 160m looked better than 15m does on my hexbeam, and a screen capture of the
panadapter can be seen at right (click to enlarge). The LoG served as the sole
receive antenna for the entire contest, driving both the TS-590SG, and an RSP-1 used
as the pandapter. The antenna produced enough signal to "set the noise"
in both the panadapter and the transceiver, even with the 3dB splitter loss. Not
only was I able to work the contest despite the challenging RF environment, I greatly
enjoyed listening to very clean and low-noise CW for over ten hours of 160m operation.
The LoG easily heard stations at all distances, from a few miles to many hundreds of
miles, all with very similar S/N levels.
A little over a month after the ARRL 160m contest, I used the LoG again to work the
CQ 160m CW Contest
. The antenna again
performed quite well and contacts were made across a similar range of distances as during
the ARRL event, resulting in a similar QSO count and final score. During this event,
I also experimented with making QSOs both with and without the 590's preamplifier enabled.
When run on 80m or 40m, this antenna needs no preamplifier, as long as quality feedline
is used. Even though the pattern gain on 160m is nearly 15dB below that on 80m, a
preamplifier still wasn't necessary
for making any 160m contacts. However,
using a preamplifier did seem to raise some of the weaker signals a bit, without
adding too much extra noise in the
; this is probably a matter of taste for each operator.
One thing that I would note is that if a preamplifier is desired for 160m operation,
the preamplifier built into any modern transceiver is more than enough. Coaxial
cable loss on 160m is tiny, and a remote preamplifier is not needed. Given that
the preamplifier is definitely unnecessary on 80m or shorter wavelengths, the choice
becomes whether the operator prefers the sound obtained by pressing the PRE button on
the rig during 160m operation. If more signal is desired on 160m, another way to
get it (and arguably a better way) would be to simply make the loop a bit larger.