[NLRS] 10 GHz & Light Youtube

[Doug Reed]

Will laser or light communications be the next NLRS group project? I 
haven't researched anything in current ham radio state-of-the-art.
It looks like most of the info on the K3PGP site is now 10 years old. 
<www.k3pgp.org>
His PIN diode receiver front-end is still one of the simpler units to 
build although it is optimized for low modulating frequencies like 800Hz 
and up to 20KHz.
Some of his experimental data shows significantly better SNR down around 
20Hz and below. QRSS slow CW anyone???

When searching "Free Space Optical communication" I followed a Wikipedia 
entry to this entry about a free design for high-speed digital links.
<http://en.wikipedia.org/wiki/RONJA>

I haven't seen any articles about using the Luxeon 3 watt red LEDs for 
communications, but evidently they are the favored answer to regulations 
prohibiting shining lasers around the sky. And they are usually focused 
by large Fresnel lenses of the kind used in overhead projectors and the 
$10 "whole page magnifying lense" that is sold for seniors trying to 
read a phone book. The "experimenter's grade" assembly would be a 
cardboard box with a hole cut in the side and the lense taped in place. 
The "professional grade" assembly would use a box made with 1/4" 
light-weight plywood.... One thing for sure, there is plenty of room 
inside the box for incidental electronics....

The receive assembly uses the same type of magnifying lense, with a 
light receiving front-end of some sort, and additional circuits as 
needed for your specific task. One of the more common suggestions these 
days is to use a 2M HT or old police scanner as the receiver for the 
system by taking the received signal and mixing it up to the 2M band and 
into the HT for demodulation. Note that any frequency within range of 
the HT receiver could be used, so keep your eyes open for crystal 
oscillator modules of various types that are within range of your 
receiver. Most of these designs use subcarrier modulation with 15, 25, 
or 30KHz subcarriers. 15KHz and 30KHz fit in well with the 2M HT 
receivers....

Keep an eye open for a simple audio-to-subcarrier modulator to use for 
the transmitter. I'd ideally suggest switched carrier frequencies of 15, 
20, 25, and 30 KHz until we know which will work best. Most HTs can step 
in 5KHz steps so they should be compatible.

 From the YouTube clips mentioned before, people have tested paths up to 
100KM with this type of equipment, from mountain to mountain. There is 
also evidence that cloud or sky-bounce with this type of equipment will 
extend past 25 miles. It might be interesting to experiment with long 
distance cloud bounce using 5Hz to 20Hz signals with the computer to dig 
the signal out of the noise. The LOWFER guys have been doing this for 
years. It would be interesting to see what kind of range we could get 
with cloud bounce in the light polluted skys of the metro area. How many 
Q's could you get just pointing a light into the sky during the 
contests????

Oh well, just something more to play with....

73, Doug Reed, N0NAS.

Scott wrote:
>
>
> Here's another good one.  I like the variable attenuator at the end ;)
>
> http://www.youtube.com/watch?v=uzIiICw36zg&feature=related
>
> Scott
> N0EDV
>
> W0ZQ at aol.com wrote:
>
>> Hello NLRS.  Here is a link to a fun U-Tube  from K7CJ working with 
>> Clint, KA7OEI, on both 10 GHz wide & narrow band, but  more fun is 
>> the Luxior LED and laser contacts at 172  km.
>>
>> http://www.youtube.com/watch?v=DPiCSG2J7To
>>
>> 73, Jon
>> W0ZQ 
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