Message-ID: <15c87a39904.marcocadeddu@tin.it>
Date: Thu, 8 Jun 2017 14:17:44 +0200 (CEST)
From: "marcocadeddu@tin.it" <marcocadeddu@tin.it>
To:  <rsgb_lf_group@blacksheep.org>
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Subject: R: LF: VLF CW transmision from Speleo amateurs in Spain
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not so "off topics" Juan :-)

and very interesting by the way: your friend made a nice job indeed!
It recall my effert to develope a 2 way voice RTX to be used while 
diving: with just a little difference...
diving in water makes much easy transmission-reception of audio signals 
instead of electromagnetic one so no antennas but piezo ultrasound 
transductors.
Absolutely nice the use of MultiPSK for the traffic :-)
I have to dig in my archive looking for the easy schematic of the voice 
RTX.. maybe your friend after the CW DXC (dx cave) wish to play with 
the phone award :-)))

Marco, IK1HSS

----Messaggio originale----
Da: luis@vigilant.es
Data: 8-giu-2017 13.09
A: "rsgb_lf_group@blacksheep.org"<rsgb_lf_group@blacksheep.org>
Ogg: LF: VLF CW transmision from Speleo amateurs in Spain

Hi VLF ..... a bit off topic but seems that this is the right place to 
talk about "almost DC" radio experiments, isn't it ?  ;-)

Got news from Juan Leandro. Not a radio amateur (yet) but strong 
enthusiast and technician who has developed
a series of electronic aids to perform communications from speleo 
amateurs inside caves with the team outside
The system was initially designed to provide a signal reference to 
measure angles from surface and then use this data
to make 3D charts of the caves. But the last version, called SUMMER can 
also be used to transmit CW to the surface
It uses a magnetic antenna at 38.4KHz

The last operation took place last weekend june 4th inside a siphon 
which included diving. SUMMER was used to inform
surface team and keep them aware about the development of the activity. 
It was a distance of 70,5m trought rock package
The design of the SUMMER is tailored to speleo needs, not radio 
amateurs. The operator terminal is a ruggerized Android
phone running "Morse Player" and sending the keying to SUMMER via 
Bluetooth. All IP66 proved and very rugged  ;-)

At surface, a regenerative Rx and two decoders were used. One Android 
with App "Morse reader" and MultiPSK in a laptop

This links to the website of the group. Sorry, Spanish only but you can 
see a lot of pictures here
http://extopocien.es/galeria-de-fotos
There is also an audio of the CW signal here. OOO copy indeed :)
https://drive.google.com/file/d/0B35G5k4xUp5VeFUwXzFaN1pkNkE/view

And a video showing the surface operation
https://drive.google.com/file/d/0B35G5k4xUp5Vck9LMEpEemRISnM/view

You will probably find interesting the description of the SUMMER 
transmitter, which is in few pdf docs at this links
https://dl.dropboxusercontent.com/u/7162072/Docs/Espeleo%20gonio/Summer%201%20descripcion.pdf
https://dl.dropboxusercontent.com/u/7162072/Docs/Espeleo%20gonio/Summer%201%20Tcontrol.pdf
https://dl.dropboxusercontent.com/u/7162072/Docs/Espeleo%20gonio/Summer%201esq.pdf
https://dl.dropboxusercontent.com/u/7162072/Docs/Espeleo%20gonio/Emisor%20summer1descRecA.pdf

A lot of room for improvement, but keep in mind that this guys are not 
looking for squeezing the last dB
but making a realiable and easy to operate system. They can not deal 
with very slow modes and all must be kept
reasonably simple, which most of the times means also, reliable. Cave 
explorers are not DX operators  ;-)

Comments and advices are thruly wellcome. Juan Leandro is one of the 
(many) readers of this reflector

73 de Luis
EA5DOM