In a message dated 12/29/2003 11:01:01 AM Central Standard Time,
topband-request@contesting.com writes:
in high local noise, would it be advantageous to put a small receiving loop
on top of a tower? In my simple mind this would at least remove the antenna
some 15 m away from the sources. Is that worth the effort?
Hi Thomas,
Putting your small receiving loop atop your tower might make things worse.
The best example I remember of that was demonstrated by W1BB, Stew Perry. In
the
1970's, Stew asked me to build a receiving antenna for him. He had serious
noise problems at his "tower" location on the cliff above the Atlantic shore
which was located in downtown Winthrop, MA. I built a multi-turn shielded loop
using 1" aluminum encased hardline and shipped it to him.
Stew called later to say that it didn't help and in fact was noisier than his
big two element inverted "V" array atop the water tower, 250' above the
ocean. Upon questioning I found that he had hoisted the loop to the top of the
100'
tower. It seemed to me that the 100' of vertical coax was doing a fine job of
noise pickup, negating the benefits of the loop. Besides that, it was in the
center of the dipole array. It took some talking, but I convinced Stew to try
the loop on the wall of the little control hut at the base of the tower, where
his station was crowded into a corner. He then realized the loop's signal to
noise characteristics. The 3' diameter loop performed like a champ in that
position, about 4' above ground. He used the loop to good advantage until he
had
to abandon the "tower" location, years later.
If it were me, Thomas, I would keep the loop close to ground with a short
feedline, but as others have mentioned, perhaps be able to turn it to null the
major noise source. An actual rotator might be a waste as the loop will likely
have little directivity to DX stations.
Best DX, Barry, W9UCW
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