I will second Bruce's comments. Re-radiated noise is almost exactly what you
are describing.
I started using terminated loops around 2000 and even though everyone said that
the transmit antennas needed to be detuned when receiving, I was stubborn and
didn't follow the advice immediately. The loops were noisy and lacked
directivity. I caved and added a circuit to detune on receive and the loops
got
quiet and were really quite directive compared to what they had been.
As a side note - I had need to install a low 80m dipole last summer
temporarily. I did not provide a means to detune it - I never thought about it
really as it was completely off my radar. It was not until I tried to use the
RX loops on 80 that I realized what I had done (or note done as the case was).
Anyway, that dipole came down pretty quickly and the loops began behaving
normally again..
Any RX antenna is going to behave similarly - shielded loop, K9AY loop,
beverage, it does not matter - if you don't detune the TX antenna or get the
RX
antenna a long way away from that TX antenna.
73 and good luck,
John KB5NJD..
________________________________
From: Bruce <k1fz@myfairpoint.net>
To: topband@contesting.com
Sent: Sat, June 16, 2012 11:58:36 AM
Subject: Topband: Receiving loops
Tim,
Your receiving antennas may be picking up re-radiation, of noise and
signals, from the transmitting antenna. Try detuning the TX antenna while
receiving. (If best receiving on the loop is with the null toward the TX
antenna, it is a indication.)
73
Bruce-K1FZ
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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