“Knallfunkensender”
Literally "Bang-Sparks-Sender".
Are you sure it's because of the radio spectrum bang? I always thought it was because of the audible bang.
If someone operated such a thing today, any guesses what the death zone for electronic devices would be?
https://www.duden.de/rechtschreibung/Funke#Bedeutung-1
¯\_(ツ)_/¯