The DCF radio in Frankfurt sends out a constant beacon signal at 77 KHz which can be received by a cheap radio module all over Western Europe:
Update – the above connections are wrong. The diagram was showing the bottom view, all wires need to be flipped over to the other end of the DCF77 screw terminal block. No harm done, it works now.
The code has been added as “dcf77demo” in the Ports library.
Sample output:
