[Laser] PIN photodiodes....

Thu, 21 Aug 2003 15:20:57 -0400

Andy,
   Thanks for the info.  I had heard that the CLD-142 would work, just hard
to find.  I looked at the PDV-V417 from Digi-Key but noticed that it's
spectral peak was more towards the visible (green) I think.  I was planning
on using 880nm diodes to do some cloud bounce experiments.  I have seen some
T-3/4 package PIN's on DK's page but was not sure how well you could focus
on the rounded diode top?  I would prefer a flat windowed device.  Your web
page has provided some useful info, what is the Spectrogram program you have
displayed on your page?  There is very little (none except me?) activity on
VHF/UHF and
Microwave down here in GA, EM83DN.  So cloud bounce expermints may be my
only way to hear any sigs!  Thanks again for the
info.....73...Bob...WA1EDJ/4...

-----Original Message-----
From: Andrew T. Flowers, K0SM [mailto:[email protected]] 
Sent: Wednesday, August 20, 2003 5:15 PM
To: [email protected]
Subject: Re: [Laser] PIN photodiodes....

Bob,

I've used two different diodes with the PGP front end.  One is the 
Clairex CLD-142 and the other is the PDV-V417-ND from Digikey:
http://www.digikey.com/scripts/us/dksus.dll?Detail?Ref=94910&Row=232509

The the CLD-142 is discontinued, but I think Moxley Electronics still 
has a few.  It looks like a TO-99 transistor with a plastic lens in the 
top.  It has a a much smaller detector area and is thus a lower noise 
device.  The digikey part has a larger detector, which gives you a 
larger target with your lens--if you are thinking of using a fresnel, 
this is the way to go without breaking the bank.  Besides, I can attest 
that weak signals will *not* be a problem on LOS pathsuntil you get into 
the tens of miles.  I'm sure other folks know much more about what is 
out there in the photodiode world, but at $5/ea it's not too bad.   Just 
make sure you order enough other stuff to avoid the $5 handling charge 
(I think $25 min).  That's usually not a problem for us hams.  The 
panasonic device you mention has less than 1 mm^2 of active area--you 
have to be right on with your lens--any light that doesn't hit it gets 
wasted.  You can do this with a good glass lens, but forget it with a 
fresnel.  The bigger the lense is the more gain you have, just like the 
dish..and like a dish and energy that doesn't hit the detector is lost.

FWIW, I can hear stuff I can't see with my PGP RX and a 4" lens.  We're 
looking at non-LOS stuff once we get some good aiming systems worked out 
(clouds, microwave radomes, etc).  There is alot of microwave activity 
up here in the Rochester area, and laser comm stuff fits in with all of 
the contesting and even weekend activity that goes on around here.  I 
have some stuff on my site that might give you some ideas, if you 
haven't looked at it yet:

http://mail.rochester.edu/~af006m/index.html

Andy
K0SM/2 FN13ed

Confrey, Bob wrote:

>     Where can I find a good PIN diode for the K3PGP front end?   I've
>looked at Digi-Key and found some (few) like a Panasonic PNZ331F.  Is it
any
>good for
>The PGP frontend?   My intended use is troposcatter, night, weak signal.
>Thanks!...Bob   WA1EDJ..... 
>
>
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