On Sun, 7 Apr 2019, DK7FC wrote:
An OM (OT!) of my radio club told stories of his early radio experiments. He had a friend in some 100m distance and they lay out a small hidden wire into they ground between their QTHs, using the earth as the back 'wire'.
Some electricity (i think they didn't call it electronics back then) hobby books for boys in the USA has descriptions of using ground dipoles for telegraphy. The transmitter was a buzzer-like circuit with step-up transformer, and the receiver was just high impedance headphones. Unfortunately i don't have the book, but i remember it also showed how to make a rhumkorff generator from a ford t ignition coil, so it must have been very old.
I also remember reading somewhere that during the war (not sure it was WW II) using amateur radio equipment was prohibited, and the ARRL advised using similar equipment, so that people don't loose their operating skills.
No doubt some people used much larger ground dipoles than advised in the books :)
Jacek / SQ5BPF