I was able to get my new K9AY loops installed and working just before the
contest this weekend. I spent quite a bit of time listening on 160, 80, 40,
and the AM broadcast band. I used two loops at right angles, with a
photoresistor used to remotely optimize the f/b of the loops. I'd like to
share my experience here, in order to see if anyone else has made similar
observations. Here's what I saw:
1. The greatest f/b ratios were seen during the daytime with AM broadcast
stations, within approximately a 35 mile radius. These are low power
stations that produce a marginal signal at my QTH. While I did not use my
step attenuator in the line and so can't provide meaningful numbers,
substantial f/b was observed when the pattern was turned away from the BC
station. A signal that was about 20 over S9 dropped to S5 off the back of
the antenna. This was repeatable with stations in other directions.
2. Listening to USA stations during the 160 contest, I noted less effect
from steering the pattern, but the result was sometimes dramatic in that an
interfering signal was dropped to a level that the desired station could
easily be copied. On DX (Caribbean only - was not hearing Europe), there
was no case where the received signal level rose to the level of that from
my 160 vertical, a top and bottom loaded 70 footer, about 150 feet away.
Shorter haul USA stations were equal in strength to what I saw on the
3. Listening to DX SSB signals near 3790, the K9AY consistently provided
readable signals from Europe when the same signals were just not
understandable on my 130 foot inverted L. The very poor ground system on my
L may have had something to do with that.
4. On 160, the K9AY loops picked up a low level electrical noise that I
couldn't hear at all on the vertical. It sounded like an electric motor
whine but varied in speed regularly. After about 1 AM, the noise shutdown
and I never heard it again. I wonder if others have experienced more
electrical noise pickup with this type of antenna than others?
My loops are 25 feet high at the apex, with the ends terminated in the
control box about 18 inches above the ground. The far ends of the loops are
about 3 feet above the ground. I used a separate control cable for the
relay and photoresistor voltages, and have a single 6 foot ground rod below
the control box.
Floyd Sense - Angier, NC