These radios were secretly constructed and used by prisoners in
Japanese prison-of-war camps during WW2 in circumstances where you
can't pay a visit to Radio Shack and purchase the bits and pieces. The
antenna also had to be hidden.

But, for things to work, there had to be a friendly news-broadcasting
station not too far away. Which did not occur very often. Long
distance short-wave stations do not lay down particularly strong
signals.

However, there has been a report of prisoners in the Far East
receiving news of the end of the war in Europe thus giving
encouragement and hope to people who had survived for several years
under the most extreme and terrible conditions.
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Reg.