[Elecraft] K3 Noise Transient measurements

[Mike Scott]

I put an oscilloscope on the right external speaker (8-ohms) of my K3 and
set up on 40M SSB @ 2.7 KHz bandwidth. The audio gain is at 9 O'clock. Band
noise is high at S-7, no signals heard. I measured steady state and start-up
noise transient voltages. Audio gain is set to Hi. 

peak-to-peak noise in steady state is 0.3 volts

peak-to-peak noise during start-up transient is 5 volts

I compute this as a +24-dB start-up blast, very startling to hear

On CW 400 Hz filter I get 0.3 volts and 3.5 volts peak-to-peak or +21 dB
start up transient. 

I believe that a signal or strong band noise needs to be present for this
effect to be heard. I went to 10M with S-0 band noise and I can not measure
or hear a startup transient at all. So if anyone tries to replicate this
problem from a quiet location, better hook up a noise bridge.

I believe that someone has noted that the effect has something to do with
AGC. I believe this to be correct as I can get the same noise blast by
turning the AGC off.

AGC settings as follows (I believe all default):
AGC Hold 000
AGC PLS nor
AGC SLP 012
AGC THR 005
AGC -F 120
AGC -S 020

Mike Scott - AE6WA
Tarzana, CA (DM04 / near LA)
K3-100 #508/ KX1  #1311