Non Radio covert communications

[Lightspeed]

Nice one HL some interesting ideas starting to come out of this.

Our friend e-bay has many low cost laser pointers on sale also much higher power devices up to 250Mw for around £25.00 those should be good for 5 or so miles range.

[Skean Dhude]

I built something similar when I was a kid. Not all lasers will damage your eyes but you don't need one. Use an LED as suggested and you can have a receiver that picks up the light. Think light switches you put across a door to detect someone walking through.

Use as you would a flashlight signal.

[Lightspeed]

I've made a little search on audi modulated laser beams. Current distance record is over 100 miles.

But this still does not come close to the heliograph distance record of 183 miles that was set in 1896!

[Steve]

Modulated IR lasers are interesting, that's what spooks use to bounce off your windows and listen to you from a mile away. If you can't afford a laser you can focus a led or similar point light source with a telescope. Put the light source where your eye would be and the beam can be focused using the normal focus control. This would get more light to the target than simply using a pin-hole and blocking the rest.

I can see Anglesea ( about 70 miles away ) from here if anyone wants to have a go :-)

[Lightspeed]

I'm intrigued at the possibilities of using lasers for line of sight signalling.

I've ordered a few to have a play with. They are very low cost now and could make a very good signalling aid to add to the GHBs

[Skean Dhude]

HL,

What you are talking about is painting the target. The missile has an IR detector which detects the light on the target and steers in. The plan just flies to a point where the missile can see it. The weapon detects the painted target, tells the pilot and he can fire anytime. The weapon just flies to its target from there.

[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

[Bug_out_Bag]

Here's an instruct able for sending audio / voice over light beam. Looks pretty natty !

http://www.instructables.com/id/HOW-TO-S...-of-Light/

BoB

[Jonas]

If you just want to tralk with your next door neighbors, an old army field telephone set in each house, connected with wire, is probably the most secure.

[Highlander]

(25 August 2013, 06:57)Lightspeed Wrote: 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.

Not if you use the rifle barrel idea for accurate targeting,..... during the day time of course

What you could do is use the rifle to hit to target, draw a line [ on the wall for instance ] along the rifle barrel, remove the rifle, nail a piece of wood around the line you have just drawn,.. wide enough to rest the laser beam on ,... then it could be used over and over without lining up each time, day or night, all you have to do is put the laser on the wood and switch on

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`along` the line you have just drawn