1 W Luxeon LED Communications over a 104-Mile Path

http://www.arrl.org/news/features/2006/07/14/1/

"Back in February, Mike Groth, VK7MJ, and Chris Long performed an amazing radio accomplishment. They communicated over a 104-mile path using LEDs as their means of communications! These experimenters accomplished this feat from perches on the south peak of Mount Barrow and Mount Wellington in Tasmania, Australia, on the evening of February 19...."

Interesting, but I'm not sure why they did it when radios work better. More secure perhaps?

I've been wanting to use LED's (actually lasers) for moonbounce communications, a much greater distance

paulr said:

I've been wanting to use LED's (actually lasers) for moonbounce communications, a much greater distance

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Just yesterday I read that laser light returned by reflectors left on the Moon in 1969 show that the Moon increases the size of its orbit by 1.5 inches per year due to ocean tides on the Earth.

Here's the article: http://www.signonsandiego.com/news/science/20060713-9999-lz1c13laser.html

PhotonBoy said:

http://www.arrl.org/news/features/2006/07/14/1/

"Back in February, Mike Groth, VK7MJ, and Chris Long performed an amazing radio accomplishment. They communicated over a 104-mile path using LEDs as their means of communications! These experimenters accomplished this feat from perches on the south peak of Mount Barrow and Mount Wellington in Tasmania, Australia, on the evening of February 19...."

Interesting, but I'm not sure why they did it when radios work better. More secure perhaps?

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I attended a conference (Gippstech) the weekend before last where the gear used for this type of communication was on display and a short talk with photos was given. Very interesting.
http://reast.asn.au/optical.php

Hmmmmmm, interesting to see there are probably more Hams here than just me...............

mmm... i love ham!

lightningbug said:

Hmmmmmm, interesting to see there are probably more Hams here than just me...............

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HAHA theres a few... I had thread run like a net check in soum time ago but cant rember much about it and cant find it now. I think there were soumwhere around 75 or so difrent Hams on there.

104 mile communications with a Luxeon thru air

I happened to run across it here:

http://www.bluehaze.com.au/modlight/index.html

Re: 104 mile communications with a Luxeon thru air

Well, if I could see someone 104 miles away it WOULD be tempting to blink something at them. Cool though.

Re: 104 mile communications with a Luxeon thru air

thats interesting that must be a heck of a colminator.

Re: 104 mile communications with a Luxeon thru air

very interesting! would have never thought lasers were at a disadvantage...

"Let us be blunt: coherent light is incompatible with the turbulent atmosphere. It will only transmit a few hundred metres horizontally before the coherent wave fronts begin to break up as they encounter constantly moving cells of higher and lower density air. Transmitted over any significant distance, the beam will suffer from deep, rapid scintillation or fading. In atmospheric transmission, coherent light beams can be far less capable of carrying recoverable modulation than an equivalent beam from a non-coherent source. Atmospheric phase and amplitude noise mostly renders heterodyne detection via a local laser oscillator impossible."

Re: 104 mile communications with a Luxeon thru air

Right in my backyard, and I had no idea. That's some seriously cool stuff! :thumbsup:

Re: 104 mile communications with a Luxeon thru air

cy said:

very interesting! would have never thought lasers were at a disadvantage...

"Let us be blunt: coherent light is incompatible with the turbulent atmosphere. It will only transmit a few hundred metres horizontally before the coherent wave fronts begin to break up as they encounter constantly moving cells of higher and lower density air. Transmitted over any significant distance, the beam will suffer from deep, rapid scintillation or fading. In atmospheric transmission, coherent light beams can be far less capable of carrying recoverable modulation than an equivalent beam from a non-coherent source. Atmospheric phase and amplitude noise mostly renders heterodyne detection via a local laser oscillator impossible."

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There are ways of compensating for atmospheric turbulence - As evidenced by the impressive range of anti-missile lasers being developed for military applications.

Re: 104 mile communications with a Luxeon thru air

Greetings!

cy said:

very interesting! would have never thought lasers were at a disadvantage...

"Let us be blunt: coherent light is incompatible with the turbulent atmosphere. It will only transmit a few hundred metres horizontally before the coherent wave fronts begin to break up as they encounter constantly moving cells of higher and lower density air....

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If you read the article referenced by the original post, you will see that the current world record for optical communications is still held by a violet laser. 248KM (153.97 Miles), in 1991.

Best wishes,
Bawko

Re: 104 mile communications with a Luxeon thru air

Right, but they had to use MCW tone operation with the violet lasers, and couple that with expensive photomultipliers. Not voice modulation...

"The photomultipliers used for receiving are devices of unrivalled sensitivity, but work best at the short wavelength (green-blue-violet) end of the visible spectrum. Violet laser light had the PM's working efficiently, with fresnel lenses 46 cm square for reception. However, in refracting more than red light, violet is subject to extreme atmospheric scintillation and absorption. This all-time atmospheric optical DX record spanned 248 km (153.97 miles), but was set with MCW tone only, not with voice modulation. "

Re: 104 mile communications with a Luxeon thru air

Bringing this thread back, because it's awesome. (What a light the CPF world lost in NewBie!)

I know white LEDs have advanced at the fastest rate of any color, but imagine how far a new red LED can shine, or with what bandwidth it could transfer data over 104mi today.

Re: 104 mile communications with a Luxeon thru air

I wonder if Saabluster could match the 104 mile figure..

Re: 104 mile communications with a Luxeon thru air

I knew there was another thread on this subject because I remembered participating in that thread, after a bit of searching I've managed to find the original thread.
Oldest Thread Merge ever - Norm

Re: 104 mile communications with a Luxeon thru air

Isn't this box-and-fresnel design less efficient (for the emitter) than an aspheric assembly?

Re: 104 mile communications with a Luxeon thru air

StarHalo said:

Isn't this box-and-fresnel design less efficient (for the emitter) than an aspheric assembly?

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You can pull 4'+ fresnel lenses from a projection TV, I dont recall the last time I saw a 4' solid glass lens, spherical or aspheric Much easier on the budget.