[Elecraft] When to use the preamp on the K3/K3S

[Bob McGraw K4TAX]

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