[Laser] New Cloud bounce system being built Optical detectors

[Tim Toast]

Hi Paul,
 
Several in here have had good results when using LED arrays for NLOS. For lower noise 
operation of the K3PGP receiver you can try using a lower noise FET in the front end like 
a 2SK170 or other exotic fets other than the regular MPF102. Cooling the detector works 
good too if you can deal with the condensation problems.
 
I think most of the experiments with LED arrays have used receiver fields of view smaller than the 
actual transmitter spot on clouds or other objects. The more of the spot you can fit on the detector 
the better, i would think - as long as background noise permits. Aparently, having the entire spot 
on the diode will give you much less scintillation than with only part of it. But that is easier done 
with a laser no doubt!
 
Good luck with it! 
- did you find an optical ham on Long Island?
 
-toast
 
 
 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Wed, 13 Jul 2011 11:46:22 -0400
> From: "Paul A. Cianciolo" <paulc at snet.net>
> Subject: [Laser] New Cloud bounce system being built Optical detectors
>     Tim    Toast
> To: "'Tim Toast'" <toasty256 at yahoo.com>,    
> "'Free Space LASER
>     Communications'" <laser at mailman.qth.net>
> Message-ID: <007001cc4174$047a7dd0$0d6f7970$@snet.net>
> Content-Type: text/plain;    charset="iso-8859-1"
> 
> Tim,
> 
> Sorry I missed this response for a while.
> I really appreciate the answer.
> 
> I found a hybrid detector amp in my pile of stuff.
> It has an  area of 5mm2 
> The peak response is at 940NM 
> Its made by advanced photonics but right now I cannot remember the model.
> Although I do remember that is much quieter than the BB  OPT301 I used
> during the one way Contact I did about 10 years ago.
> 
> Here is the filter am using  in front of the device. 
> 
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=310313273043&ssPageName=S
> TRK:MEWNX:IT#ht_500wt_922
> 
> Only 8% transmission loss and very sharp skirts
> 
> The last time I did this see here
> http://www.rescueelectronics.com/Optical_Comms.html
> 
> I used 814 940 LEDS I stripped from CATV remotes.  Many Many hours of work.
> The diodes I used were approx..  25 mw/SR  with 50% beam width  of 50
> degrees
> 
> These diodes:
> http://www.paralight.us/uploads/pdf/EP2012-350IR1.pdf
> 
> are the one I will be using for this project.
> Each diode is  1 watt/SR in  50% beam width of 10 degrees.
> 
> The  100 diodes will be in any day now.
> The array will have an output power of greater than 100 watts/SR.
> 
> The frequency of choice will be 450 HZ  divided down from 1.8432 Mhz
> crystal.
> I will investigate this list of detectors Tim.
> 
> But for the moment I wonder if it is possible for some to build a detector
> amplifier that would have a noise advantage over
> manufactured hybrid.
> 
> 
> Paul A. Cianciolo
> W1VLF
> http://www.rescueelectronics.com/
> Our business computer network is  powered exclusively by solar and wind
> power.
> Converting Photons to Electrons for over 20 years