In article , "Frank
Dresser" writes:

All bets are off in the case of a regenerative receiver being used with the
detector's regeneration control turned up into the oscillation region in
order that an anticipated CW signal could be heard more clearly.


ISTR reading once that regen sets (and the Navy was using plenty of them,
especially for LW and VLF) really were a major problem. To copy CW, you do
have to adjust so the set is just barely oscillating. Fortunately, most Navy
regens had one or two RF stages ahead of the detector. I had an RAK VLF set
that was just incredibly sensitive and selective, with 3-gang tuning and
individual trimmer knobs on both RF stages. There was an HF edtion of this set
too.

The posted page also says the Germans were suspected of being able to listen
in on the 455 kc IF radiation. This would even more tenous than local
oscillator radiation. Again, not impossible, but I doubt long range
detection could be done with any reliability.

IF radiation would be pushing it, but it has the advantage that there's only a
very narrow band of freqs to monitor. An advantage (for the U-boats) of regen
rx is that one could listen to the enemy transmitter freqs, which you'd be
monitoring anyway, and a steady "carier" would mean a nice plump target nearby.

As for code cracking and good old "loose lips" in dockside bars, when enemy
U-boats are sinking your ships, you don't *know* why, you just grope for
possibilities, and radio receiver radiation was one explanation.

Along those lines, our Navy did fool the U-boats into thinking that we were
picking up on their super-regen radar detectors, thus causing them to shut
those off, making it easier to catch them on the surface. --Mike K.

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