Celestia Forums

Back in the early 1970's, we used to carry a portable AM radio during our star gazing nights, as a crude method of monitoring approaching storms by static/lightning crashes. Oddly enough, on keeping the radio on a fairly blank frequency (then), about 530Kh, we started picking up a repeating signal (dash/dot, dash/dot/dot/dot).

It appeared almost every night that summer, then faded out forever. I'm going to assume that my cheap AM radio may have been picking up some harmonic beacon from a different frequency, but hopefully someone out here may know first hand what we were listening to?

Most likely a "Navigational Directional Beacon" (NDB) or "VHF Omni-directional Radio Range" (VOR), sending out signals in Morse Code. They're navigation equipment for airplane pilots.

If it were to have been that, my guess would be that it was an NDB - they transmit in the kHz frequency ranges... VORs transmit up in VHF mHz ranges. If you could remember the code sequence we could actually look up which NDB it was lol.

As for the sequence, I'm not sure beyond possibly repeating itself once every ten seconds or so.