I've been watching this thread with interest over the last few days, and
would like to add my two penneth.
Until two weeks ago, when I finally completed my remote 8-element receiving
array, I relied on 3 separate receive antennas.
1) A pennant, facing NNW, about 300 feet from the house, shack, and
powerlines.
2) A rotatable flag, about 100 ft from the house etc
3) An unshielded "magnetic" loop about 50 ft from the house.
I found the following.
The pennant was best at sunrise for signals arriving from NW - On the odd
occasion when I swung the end around to NE, it was best in that direction as
well. I think this is explained by its good separation from noise sources.
The flag was particularly poor under almost all conditions, in spite of the
fact that I had gone to some effort to reduce common mode coupling from the
feeder. (I used the transformer on Tom W8JI's website) I think this may be
because at 100 ft, it is still too close to the house and power lines.
The loop was surprisingly good in terms of signal to noise ratio, in spite
of being much closer to the house. It gave me my first G contacts (G3PQA,
G3XGC) I have often wondered why this is, knowing that at 50 ft distance,
it is too far away for the 'H-field only" argument to be used. It is
resonated with series capacitance, and fed via 2x4:1 DC isolated step down
transformers. Presumably the transformers are also good at keeping out
common mode signals picked up by the feeder. Do people think that this is
the reason why the loop is good? I must say that the feeder is arranged in
a much more symmetrical way than the feeder for the flag.
To confirm the theory about noise reception from distant sources, I took
both my loop, and a short vertical with a FET preamp, out into the country,
away from local noise, for comparison. Surprise surprise - the signal to
noise ratio on the signals from the ZL digi's was identical on each antenna!
The theory seems to hold up in practice!
So while I have to agree with those who say that, in theory, there should
not be much difference between small loops and other antennas, I do find
that my loop works particularly well in a domestic environment. I like to
think that this is because the arrangement I have gives it good isolation
from common mode signals picked up by the feeder, but for that reason I
would have thought that the flag would have given better results than it
does. I don't really have the answer to that.
The remote steerable array that I now have out in the country beats the
socks off all of them, not only because of its pattern advantage, but
because of its distance from most of the man-made noise. One thing I do
find though, is that the QSB is much deeper on signals being received on the
array. Do other people using directional Rx antennas find the same thing?
I have arranged my audio distribution such that I can listen to the loop in
one ear, and the array in the other, for a degree of diversity. I can't
make the signals coherent, because the array is 20 miles distant, but I
still find that the loop fills in the really deep QSB holes that the array
gives.
Another advantage of using the remote antenna, is the perfect QSK I now
enjoy!
73, Greg, ZL3IX
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