[Laser] Recent NLOS experiments using IR Leds

[Kerry Banke]

Mike - That 34W is the input power to the Leds. About 2W is dissipated in the series resistors.  I think the Leds are rated for about 0.1W output each with the 0.1A that is passing through them.This definitely lights up the back yard looking through a CCD camera! A fan is used to cool the array as the Leds are spaced closed together.
   - Kerry N6IZW

mike1 at mgte.com wrote:
  Hi Kerry,

I'm going to send myself this msg also to test and see if 
bellsouth.net is still banned. I think they may but it's worth a try.

Question: Tx input of 17v @ 2A = 35W (at least math wise) so, bottom 
line is 35W the transmitted power and if not what is the output 
power?

I've been buying IR modules off ebay with a power of 500mW each and 
about 40 each CD optical heads with unknown power. (I'll have to do 
some disassembling to get to them, though for testing)

Wish I had someone in the Pensacola area to do cloud bouncing with. 
We have clouds MOST of the time. 

Keep up the good work. Experiment details are ALWAYS acceptable. We 
can all learn even by mistakes.

Best Regards,

Mike Couture
Milton, FL
30.590N
-86.963W


On 27 Apr 2008 at 7:39, Kerry Banke wrote:

> Last evening K6QPV and I completed our first NLOS one way contact
> using an array of 200 IR Leds at a distance of about 3 miles. The
> weather conditions were clear skies with some haze. The LED array was
> sending PSK31 text of N6IZW DE K6QPV which was received with
> essentially perfect copy when the stobes of passing airplanes did not
> interfere. Unfortunately the NLOS path is in line with the landing
> pattern for a local airport. The Tx array power input is 17V at 2
> Amps peak. The Leds are of the type used for IR remote
> controlsoperating in the 940 nm region. The Tx array is pinted at the
> optical horizon towards the receive site. The receiver is a 7mm area
> pin photo diode in the K3PGP configuration and has a 730 nm long pass
> filter in front to reduce unwanted light interference. The receive
> optics is a 12" microwave dish covered with Aluminum tape. This
> appears to work much better in picking up a broad area signal than
> the 5" glass lens system I have. The pointing is
> very non critical as the Leds have a 40 deg beamwidth and the scatter
> is over a broad area on the horizon. 
> When sending a pure tone the signal was about 15 dB above the noise
> in a 1 Hz BW. 
> 
> Kerry N6IZW in San Diego
> 
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