ВЭФ 12 (Astrad VEF 12 Project) - including a transistor tutorial

[Terry]

The very early crystal radios were made by soldiers in the war. 

Which war? There was no public broadcasting as early as WWI - and eavesdropping on army radio traffic would not have been popular with the authorities!

Once 2MT started up - followed, of course, by 2LO at al - it was an entirely different ball game.

During WWII, servicemen did experiment with simple radios, though many of them did not use 'crystals', in the accepted sense, at all but relied on anything that could be made to work. For example, rusty razor blades, of which there was no shortage, were popular for detectors I believe ...