Ham Radio Technology Used in Thailand Cave Rescue

UK radio amateur John Hey G3TDZ (SK) designed the special low frequency radio equipment, the Heyphone, used in the recent cave rescue in Thailand

Naturally I got interested in the technical aspects of the cave rescue in Thailand, particularly communications.

They used the “Heyphone”, a voice radio designed by a UK radio ham, John Hey, G3TDZ, as open-source hardware specifically for cave rescues.
It uses upper (single) sideband voice on 87 kilohertz in the VLF (very low frequency) band. (That’s what it says — 87 kHz is actually LF).

The “antenna” consists of two stakes driven into the ground about 20m apart. Enough of the current between them fringes outward to couple to another antenna up to a few hundred meters away (or down).
— Phil Karn KA9Q

John Hey passed away in 2016 so he didn't get to see his work used here. But ham radio should get some of the credit.

Phil Karn KA9Q (Facebook) - https://facebook.com/phil.karn.98/posts/10155276627256486

Phil Karn KA9Q (Twitter) - https://twitter.com/ka9q

John Hey G3TDZ Heyphone Cave Rescue Communication System - http://bcra.org.uk/creg/heyphone/