Ed's reference to weak signal copying is probably different than any
of you have ever experienced, with or without QRM.
He's concerned about copying off the moon, EME, signals that are just
above but mostly just below ESP level in a sky noise environment.
My experience, in listening for, and working thousands of CW QSOs on
2M EME in the '80s and '90s is that firstly all receivers aren't
created equal. In that time frame, ICOMs were unfortunately useless,
probably because of undue phase noise (??). The best that (suited
me) was the Kenwood TS-930, mainly because of its outstanding NB and
its ability to shape its IF BW. I used 500Hz IF filters, and
external audio filtering. First the passive filtering that was
available in the K'wood speaker, and then (in series with) the Autek
QF-1A active filter system. I could vary the center frequency as
well as it's shape and width. I estimate that I left it set for
about 25Hz in BW and a center frequency of about 400Hz, which was my
preferred receiving CW pitch/tone. Then by accident I discovered
that the cheapest RS muffed headphones (series 10 I believe) had a
self resonance at about 400 Hz.
When fine tuning a very weak CW signal, when I hit the 400Hz point,
in my narrow overall bandwidth, and resonant headphones, it seemed to
just jump out at me, maybe as much as 10 dB, with no preceptable
ringing. With the fine tuning mod installed in the 930, 1 Hz tuning
steps didn't seem to be a problem.
I hoping that with my newly assembled K3 and it's APF, I will be able
to assimulate the same EME detection capabilities. In todays EME
equipment, the ability to phase lock all stages (LOs) of the
receiving system to a 10 Mhz standard, will eliminate an unknown and
utilize the fine tuning capabilities of the K3. If all else fails I
still have my QF-1A and cheap RS headphones to fall back on !
Chuck, W7CS
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