[R-390] Gain drift

[dog]

Larry, Renee,

What I mean about the sensitivity around the antenna inputs is that when 
I wave my hands, fingers or an antenna near the antenna input ports, 
there is activity in the noise level. I find nothing wrong with the 
cables from the relay and there's no sensitivity there.

I did notice the gain drift again last night with the AGC mode. Today 
I'm trying it in MGC mode and so far the gain drift is much more 
noticeable in that mode. I'm going to start from the input to the IF and 
work backwards to the input. I've got some tube extensions so I can put 
signals into each stage as I go along, much as what Renee and others 
have suggested. I've been thinking about this for a while. My sig gen 
has a 50Ω output so I'm going to have to be sure I put the signal either 
through some small capacitor or find a good place in the circuits to do 
it. I tried some of the E ports casually, but that didn't seem very 
effective.

Sometimes I wonder about the AGC circuit. But this MGC drift is much 
more noticeable. I'm sure the AGC is trying to compensate for that.

I've been putting a fan on the rx to try to get it cooled down a bit 
quicker between sessions. It's a slow process when it's not just a basic 
fault.

The bandswitch is quieter especially on a single band, but I still get 
clicks switching between bands.