[Elecraft] AF setting corrupting accurate MDS test

[Rob, K6RFH]

Hello,

I have been beating my head trying to figure out why the MDS on my K3
(serial 2002) was so poor.  I've been using the receiver sensitivity test
plan from the Elecraft XG2 RECEIVER TEST OSCILLATOR, and getting a (preamp
ON) MDS of -123dBm. 

Tonight I decided to run this to ground to see why If could figure out why
my radio's performance was so poor.  After checking the obvious things like
the XG2, cable, and power supply, I decided to look at the speaker terminal
voltage on an oscilloscope.  During the tests I had both AF and RF gain at
maximum.  What I discovered is that the speaker signal actually clips at
that gain level.  I backed off the AF gain until I got a nice looking
sine-wave, and recalculated the MDS.  -134.5dBm -- as advertised.

I thought this might be of interest of others who might be testing their
unit's receiver sensitivity.

Rob
K6RFH
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