"The RF gain control does indeed control the RF stage on the 2B.
If you have problems with overload on those receivers you most likely have a
leaky capacitor somewhere in the AGC circuit or a tube with grid to cathode
leakage. The AGC or AVC as they call it, is a very high impedance circuit
and any
slight leakage screws up the whole thing. You can not even put a high
impedance voltmeter or VTVM anywhere on the AGC line as it will load it
down."
Response: The rf gain control adjusts the avc base bias voltage, which is
applied to the rf amplifier tube. The problem was that the voltage was
never going negative enough to reduce the gain sufficiently to block
overload. There was bleed through. The voltage was changing as measured
with a Tek scope using a 100X probe. The voltage generated in the antenna
step up transformer was offsetting any negative bias voltage used to reduce
gain. What I needed was something that would reduce the gain of the rf
amplifier alone, which is why I used the swtichable attenuator. Except for
that overload, the receiver worked well.
73, Colin K7FM
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