Re: ULF: EbNaut message transmitted from ground loop

[John Rabson <john.rabson07@gmail.com>]

Cave-to-surface communications makes extensive use of earth current systems and these have been a recurrent theme in the Cave Radio & Group Journal (ISSN 1361-4800).

See for example issue 55 (March 2004) http://bcra.org.uk/creg/index.html: 

An Earth-Current-Based Cave Intruder Alarm

John W. Newman and his wife Jane own a cave in Kentucky, USA, which is home to an endangered species of grey bat (myotis grisescens). As warning notices were insufficient to keep out intruders, an electronic alarm system was devised.

 

Nothing New Underground - WW1 Trench Communications

Cave radio, like trench communications in WW1, depends on the propagation of electrical signals through the earth, and we still have things to learn. The diaries of Ernest H Hinrichs (US Signal Corps 1917-1919) are reviewed by John Rabson.

73 John F5VLF

On 7 Apr 2019, at 12:49, Jacek Lipkowski <sq5bpf@lipkowski.org> wrote:

On Sun, 7 Apr 2019, DK7FC wrote:

An OM (OT!) of my radio club told stories of his early radio experiments. He had a friend in some 100m distance and they lay out a small hidden wire into they ground between their QTHs, using the earth as the back 'wire'.

Some electricity (i think they didn't call it electronics back then) hobby books for boys in the USA has descriptions of using ground dipoles for telegraphy. The transmitter was a buzzer-like circuit with step-up transformer, and the receiver was just high impedance headphones. Unfortunately i don't have the book, but i remember it also showed how to make a rhumkorff generator from a ford t ignition coil, so it must have been very old.


I also remember reading somewhere that during the war (not sure it was WW II) using amateur radio equipment was prohibited, and the ARRL advised using similar equipment, so that people don't loose their operating skills.

No doubt some people used much larger ground dipoles than advised in the books :)

VY 73

Jacek / SQ5BPF