Back in 2010 I was playing about with light waves with many other stations in the North East of England.
We had great success with Stuart G8CYW's 80m<>25KHz lightwave transverter, 1w Red LED's and Fresnel lenses and ended up making a best Dx of 117KM with Line Of Sight paths.

The time has come to try out Non Line Of Sight paths, this was spurred on by some chat on UKNanowaves group at https://groups.io/g/UKNanowaves/


Basically i'm now looking to achieve optical communications where the two ends of the path are not visible from one another, usually due to the curve of the earth or hills etc. This has been done before and to a much greater extent than i will be documenting here, please take some time to read up on the VK7 activity with NLOS Optical Communications: https://www.reast.asn.au/information/optical-transmissions/


The following sections will describe my very basic system for the attempts and some results along the way, hopefully you will follow suit and join in the fun!

Tx System
Rx System
Tests


If you happen to subscribe to DUBUS back in 2008/9 you will have a copy of the articles about VK7 NLOS Optical Comms which is well worth a read, unfortunately it's not available online but you can get back copies if you subscrible... Fortunately most of the information is available in the blog on the site above.


The method of NLOS comms basically uses the scattering of light by the water vapour in the atmosphere, usually clouds but that is not a requirement. This is in the forward direction, so you need to beam your light towards a mid point of the path between the Tx and Rx, Off axis scatter is possible but is weaker. No reports of optical comms with enhancement like tropo ducting/mirages have been reported yet so there is hope ;-)


Currently all my tests have been done by myself but hopefully there will be some more interest from local and distant stations to save a lot of driving about to /p sites for tests!


I hope you find this useful and welcome any comments.