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
J
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
