Tree wrote:
> I have often found my SSB filters to be more useful for EME work than
> CW filters. However, with lots of QRN, I think the CW filters do help.
>
I agree with Tree. For MF/HF/VHF terrestrial weak signal CW reception I
have found over the decades that I seem to do best with a hardware
filter bandwidth no narrower than 1000 to 1200 Hz. Super narrow
filters only helped me when signals were very crowded _and_ very strong
-- think Sweepstakes. The bulk of my experience has been with:
a. Collins 200 Hz filter in the 75S-3 and 75S-3B receivers;
b. Kenwood 270 Hz filter in the low IF of the TS-180, TS-850, and
TS-940 transceivers;
c. "Stopping down" the VBT control below 500 Hz or 400 Hz cascaded
Kenwood or Inrad filters in the TS-940 and TS-950SDX.
Perhaps super narrow filters result in ringing or other noise background
artifacts that are of the same approximate magnitude as the desired weak
signal(s). However, some years ago someone else mentioned "stochastic
resonance" as a psychoacoustical effect that was consistent with my
observations. As I recall the thrust of the explanation, sometimes the
addition of wideband noise helps the human ear/brain more easily detect
a tone or narrowband signal.
Bud, W2RU
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