Showing posts with label communications. Show all posts
Showing posts with label communications. Show all posts

20 Dec 2014

Optical communications - over the horizon (NLOS)

The DX record for communications at optical frequencies is phenomenal these days. There is a growing interest in communications over non line of sight paths (NLOS) using cloud-bounce or clear air scattering. To my knowledge, in recent times experiments are (or are about to start) by F1AVY, VK4EBP , VE7SL and G3XBM (when fit again). I am sure there are others too. Weak signal modes certainly help. I used QRSS3 over an 8.5km NLOS path, but much further has been achieved.
 
See http://en.wikipedia.org/wiki/Non-line-of-sight_propagation .

A couple of useful optical Yahoo groups are:

Australian Optical DX   https://groups.yahoo.com/neo/groups/Optical_DX/info

UK Nanowaves              https://groups.yahoo.com/neo/groups/UKNanowaves/info  

18 Jan 2014

Optical Comms in Vancouver Canada

This morning I received an email from Steve, VE7SL, reporting on his experiments with VE7CA over a 2-way distance of 54km using red LEDs.  They are doing really well and Steve is writing an article for a Canadian journal. They seem to have been encouraged by my own modest efforts,which I hope to restart before too long. At present my poor fitness and temporary inability to drive because of the stroke are real handicaps.

Image of optical path spanned from VE7SL