[R-390] Frequency Shift With AGC Level

[Jim Miller]

I've noticed that with the BFO on a strong carrier, when I lower and raise
the RF Gain, there is a slight change in beat note pitch, maybe 100 cycles
or so.  This doesn't happen on my other 390a.  Have swapped IF modules but
no change  Only does this on the lower bands where I think an extra mixer
stage is switched in, so I suspect gain changes in the RF deck are maybe
pulling the 10 Mhz oscillator slightly.  The receiver has very good
sensitivity.  Bad tube maybe?  Any ideas?
Jim N4BE