Non Radio covert communications

[Lightspeed]

The laser pointer suggestions above take the light tube communication link idea to a new dimension.

Here’s where I've got to so far:

Laser pointers of 1mw to 5mw can be picked up on e-bay for less than £5.00 each

Green lasers have greatest perceived brilliance to the human eye. They also have good daylight visibility and create a visible beam particularly when used at night. This helps with alignment and could be a useful search and rescue beacon effect, but is bas for Opsec.

Red lasers have less perceived brilliance than the green ones. They do not create a visible beam in normal night time conditions , this is good for Opsec but makes targeting more difficult.

Beam width of low cost laser pointers is typically around 0,05 degrees
These low powered lasers are very visible at ranges of up to 2 miles, but alignment between sending and receiving stations is very sensitive.

Mounting the laser pointer in a ½” pvc tube that extends well beyond the laser head will help aiming and alignment as well as reducing the chances the transmitter being observable from oblique angles.

I'm going to test red and green lasers in fixed aligned tubes, sending morse code simple on off pulses between Observation posts. This is the most low tech, reliable, and Opsec secure system I can come up with.

Another option is to send and receive a voice message over a laser pointer beam using simple components, and range for that transmit receive arrangement will be in the region of 0.5 to 1 mile in clear night time conditions. Details link on how to do this below. I won’t be playing with this way of signalling as the added complexity outweighs the advantage of voice communications for me. If anyone does decide to try a VOLB (Voice over Laser Beam) solution, please let all of us know how you get on.

While searching hardware available I unearthed a low cost gizmo from China that incorporates a weatherproof LED torch with white light, UV light and a little 0.5mw red laser. This might be a useful signalling device, for the EDC? Link below

Here are the links:

How to transmit voice over laser pointer ( configuration)
http://www.youtube.com/watch?v=HKRPfa66_po

Calculation of 2 mile effective communication range for a 5mw laser
http://www.discovercircuits.com/dc-mag/I...1/pg-2.htm

Chinese LED light gizmo that incorporates a low power laser
http://www.ebay.co.uk/itm/200941868054?s...1423.l2649