Alex NS6Y wrote:
In my reading about green radios I can't afford (but want anyway) and in
various readings I've heard that detecting the 455-kHz LO of a superhet
isn't all that hard, and that for instance in countries that require a
radio license, they use such techniques to check if people in their
houses have radios (or TVs) that they're not on record of having licenses
for! And, in a lot of the military radios, the shielding is VERY good so
that detection is much harder to do.
---------------------------------------------------------
In 1940 the SWBC radio for use by passengers, on the ship that was used to
evacuate a bunch of us youngsters to Africa, was put into a solid locked
metal box. I believe that this was to prevent U-boats detecting any
radiation from the receiver, most likely a superhet. The loudspeaker was
outside of the box and there must have been an external antenna. Maybe
overkill or wishful thinking.
73,
Geoff
GM4ESD
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