[Elecraft] RF gain sweet spot

[Edward R. Cole]

I'm guessing this "effect" is an artifact of the AGC parameters and 
the level of ambient noise.  I would love to see a chart of AGC 
level, K3 gain, and RFG bias voltage.

I see a flat zone between RFG at maximum and at 3-o'clock position 
when I either have no preamps activated and when I activate the PRE 
(internal preamp).  Gain appears flat over that range and I hear no 
change in audio level with antenna connected.  Remember that I have 
extreme hearing loss so it may mean I unable to hear the change even 
if there is one.

When I run my ARR preamp, the s-meter indicates S4.5-S5 and the 
s-meter immediately rises when I rotate the RFG to a lower 
setting.  There is no flat region.  Since my preamp has 24-dB gain 
and K7WIA is using a preamp with 15-dB gain, they are not exactly 
compariable.  The approx. 9-dB extra gain may be saturating the 
follow on Rx circuits.

A precise measurement of SNR (with a weak signal) vs RFG voltage 
would be interesting.

Perhaps Eric or Wayne will comment.


73, Ed - KL7UW, WD2XSH/45
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