One of the topics I've discussed with with noted engineers has to do
with use of a Preamp and use of the Attenuator and use of the RF Gain
control. In general the optimum legacy receiver performance occurs
when the receiver noise floor is some 10 db below band noise. Being
such, how does one attain this? If the no signal band noise is S-5 or
-97 dBm, and receiver noise floor is -133 dBm {i.e K3S}, this says one
should use a combination to total 26 dB Attenuation and RF Gain
reduction. Certainly one would NOT want to have a Preamp engaged under
these conditions. Likewise, if the band noise is -121 dBm or about S-1
and the receiver noise is -138 dBm {Preamp engaged} one might wish to
reduce the RF Gain a bit.
From experience and my observing other hams operations, many seem to
think more gain is needed to hear or pull out weak signals from the
noise. I find the proper use of the Preamp and specially the correct
amount of Attenuation and RF Gain reduction, weak signals seem to pop
out of the noise.
73
Bob, K4TAX
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