via the RSGB: Ham-designed comms support cave rescue

The dramatic rescue of twelve young footballers and their coach from a cave in Thailand was facilitated, in part, by communications technology developed by British radio amateur John Hey, G3TDZ. Ordinary radio signals don’t penetrate the solid rock surrounding caves, but very low frequency signals can do. Around the turn of the Millennium John designed a system that became known as the HeyPhone, which could penetrate some 800m of solid rock and provide reliable two-way voice communication. It used single sideband operating at 87kHz, with novel antenna techniques to couple the signals between units. The HeyPhone was featured in the January 2002 edition of RadCom. Unfortunately John became a silent key in 2016 but he saw his equipment used in countless cave rescue and other applications. You can read more about how his work helped save the Thai footballers on the Hackaday site, via

via Radio Society of Great Britain – Main Site