[Laser] Progress with NLOS IR laser scatter project

[Cliff Buttschardt]

Kerry, that's just great!  Cliff K7RR

Kerry Banke wrote:
> 
> Last night we ran the first try at an experiment to detect a  1W, 910 nm
> laser at a NLOS location about 3 miles away at the home of Greg Bailey,
> K6QPV. The result was a signal 30 dB above the noise.   The laser beam has
> been expanded to about 4 inches for safety as well as to provide a larger
> area for scatter.  The laser was one of several I purchased off a web
> auction for less than $15 & was  powered by a 50% duty cycle square wave at
> 172 Hz.  The elevation to the horizon from the Tx side was about 5 deg so
> the laser was elevated to about 7 degrees. The horizon was a tree & home
> covered ridge between the two locations.   The signal was detected using a
> 4" lens ahead of a K3PGP style Pin detector with MPF102 amp & no bias
> resistor. The detector diode is rated at 10 pF capacitance with no bias &
> 1mm square active area. Speclab software was used to detect and display the
> signal which was easily found within a couple of minutes as the path had
> been fairly carefully plotted on a map.  The receiver was pointed just
> above the horizon in the direction of the transmitter so I guess  this is
> really forward scatter rather than back scatter.  I believe the optics on
> the Tx end is far from optimal so I need to work on that. The next step is
> to try actual communications using Andy's LaserScatter software.
> I have a Jpeg screen capture available I can send. I'll also have a picture
> of the Rx setup during the test soon.
>   - Kerry N6IZW -
> 
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