Radio Wolfsschanze Horen -

The old Wolfsschanze radios used thermionic valves—vacuum tubes—that were incredibly durable. In the late 1950s, a malfunctioning Soviet timer left one transmitter on a loop, broadcasting a pre-recorded reel-to-reel tape of weather codes and readiness checks. The antenna, hidden in the remains of Bunker 13 (Hitler’s own quarters), was partially buried under rubble, creating a ground-plane effect that allowed the signal to "skip" unpredictably across the ionosphere.