[Milsurplus] Radiation from a regenerative detector.

[Hue Miller]

Here's another fact I forgot to mention: 
Regarding U-boats listening for convoy communications:
No one has reported any documentation on EXACTLY what 
HFDF equipment U-boats might have carried, as for the
antenna and some kind of DF adapter for the receiver. 
There MAY have been a single experimental setup, but
from the available docs, HFDF was NOT possible for 
U-boats.
One of the referenced links had an account talking about
convoy HF communications. That I would guess means
2.5 Mc/s band voice communications, because CW 
via the usual LF or even on HF would be, first, too 
powerful for just short range use, and second, likely
too slow for close-in convoy maneuvering.
In the account I read, by a U-boat captain, published
in Sea Classics magazine, the U-boat listened on the
2 Mc/s band. To no success.
-Hue Miller