[HBR] Regenerative communications receiver

[Martin Marris]

>>There's a good Wiki article at:
https://en.wikipedia.org/wiki/Proximity_fuze
<<

Thank you. That article is really interesting in describing the circuit,
which used subminiature tubes. Basically:
--An oscillator that transmitted a signal.
--An autodyne detector that received any reflected signal.
--Because of the high relative speed between the shell/bomb and the target,
the reflected signal would move rapidly in and out of phase with the
transmitted signal.
--These rapid phase shifts created an audio tone of 200Hz-800Hz.
--The audio was sent through a bandpass filter tuned to this tone.
--If the tone was present, it triggered a final thyratron tube and, "boom."

I'd love to see the bandpass filter circuit they used! I've just spent a
certain amount of time building a subminiature-tube CW bandpass filter with
a center frequency of 650Hz. I bet their circuit was a lot better than my
improvisation.

It's also amazing how large the proximity-fuze industry was: something like
$1 billion worth, during the course of the war. The price fell from $732
each, to $18 by the end of the war.

Martin