On Nov 18, 7:44 am, "COLIN LAMB" wrote:
Although I am not familiar with an additional if stage, it seems there would
not be much advantage in adding such a stage. Any additional gain would be
at a cost of reduced dynamic range.

I would be more inclined to think it was a product detector circuit, using a
6BE6.

Colin K7FM

A product detector was also my first thought, but why the IF can?

73,
Jeff