[A-DX] SWRG#56, 7780 kHz, via US remote, relevance: "Longwave underground"

[Roger]

"..........From Hackaday:

Ham-designed Gear Used in Thailand Cave Rescue

Al Williams
11 July 2018

Unless you live in a cave, you've probably heard a little about
the thirteen people - mostly children - trapped in the Tham Luang
Nang Non cave in Thailand. What you may have missed, though, is
the hacker/ham radio connection. The British Cave Rescue Council
(BCRC) was asked for their expert help. [Rick Stanton], [John
Volanthen] and [Rob Harper] answered the call. They were equipped
with HeyPhones. The HeyPhone is a 17-year-old design from [John
Hey, G3TDZ]. Sadly, [G3TDZ] is now a silent key (ham radio
parlance for deceased) so he didn't get to see his design play a
role in this high-profile rescue, although it has apparently been
a part of many others in the past.

The HeyPhone is actually considered obsolete but is still in
service with some teams. The radio uses USB (upper sideband, not
universal serial bus) at 87 kHz. The low frequency can penetrate
deep into the ground using either induction loop antennas like
the older Molephone, or - more commonly - with electrodes
injecting RF energy directly into the ground.

You can find a very detailed article about the radio from 2001 if
you want more details -- https://bit.ly/2JikD5a. The system is
somewhat dated, but apparently works well and that's what 
counts............................."

https://bit.ly/2JikD5a   ====> 
http://bcra.org.uk/creg/heyphone/pdf/descent-octnov-2001.pdf    (102 kb  
PDF)

====> 
https://hackaday.com/2018/07/11/ham-designed-gear-used-in-thailand-cave-rescue/

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The entire SWRG#56 spectrum as a collage:
https://www.dropbox.com/s/ht6gygd24gl153h/2018-07-13_SWRG56_7780kHz.png?dl=0
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
roger