[ARC5] Your deaf receiver.

[Kenneth G. Gordon]

The 12SF7 is ONLY used in the AN/ARC-5 receivers at the 2nd IF, and its base diagram is 
very different from the 12SK7. Plugging one into a BC-454's, or an ARA's, second IF stage 
will "confuse" many of the connections in that stage.

If a 12SF7 is being used in this BC-454, it is no wonder the gain is down!!!!!

The 12SF7 has an added diode inside the tube. This is where the AGC voltage is taken off 
so that the BFO can be either on or off without effecting the AGC circuit.

The AGC circuit in the AN/ARC-5 receivers was much improved over that in the earlier 
receivers.

Ken W7EKB

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