Aloha and thanks to all who responded; the following
pretty much reflects the majority of replies to my
question:
> You are probably experiencing poor isolation on the antenna switch.
> To roughly check this, listen to those weak signals while switched to the
> DL, then disconnect all the antennas and see if you still hear any signals
> while still in the DL position.
I did this, and sure enough, nothing from the rcvr of the Omni. Others
pointed out that our rigs are typically well below -100dBm in
sensitivity, even in the wide SSB IF mode, and the typical
coax and wafer switch has only 30("poor") to 60 dB(at best) isolation.
Even with the typical remote antenna coax switch, signals have
been heard, even DX ones, with the remote switch placed
to an open connector; reported by a couple of you.
Lack of complete coverage of the inner conductor by the coax
shield is another path for feed through; many coax cables have
85% or less braid/shield coverage. "Best" cables have foil wrapping
as well as high percentage braid coverings. (CB coax runs about 85%.
RG213 runs about 95%. 9913 is one of best, it has foil and braid. )
Using the more "open" covering coaxs, enough rf can get in for
our very sensitive rcvr front ends to "hear".
Others reported the distances with which they communicated while
switched to their dummy loads! One fellow goes to his dummy
load for local community QSO's! Another, his light bulb DL was
also a fine local QSO completer!
Summary: Don't worry about it, "it is a de minimus problem!"
And, don't bother to ground the case of the dummy load. Use quality
coax feed lines and jumpers.
73, Jim, KH7M
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