[Laser] daylight receiver

[Walt Rauscher]

Andy,
	On K3PGP's web site is a daylight front end. The basic difference is that
the photo-diode is biased, photoconductive mode rather than photovoltic
mode. There is a sensitivity loss due to higher noise but a much wider
dynamic range.
	I have used the Red covers for LED displays as a filter (look at old
calculators and other stuff that used LED numeric diplays). While not as
effective as a good narrowband filter it does help. If I remember correctly
you can get about a 10dB improvement in SNR.
	I other suggestions are also very good. Look at some telescope building web
sites for ideas on reducing stray light in your optical system.

have fun
walt

-----Original Message-----
From: laser-bounces at mailman.qth.net
[mailto:laser-bounces at mailman.qth.net]On Behalf Of Andrew T. Flowers,
K0SM
Sent: Wednesday, June 09, 2004 3:50 PM
To: laser at mailman.qth.net
Subject: [Laser] daylight receiver


Does anyone have a design for a good daylight receiver?  My K3PGP front
end won't hear much in daylight.  I'm not looking for something that is
super sensitive--just good enough for a LOS QSO on a sunny afternoon.  I
was thinking about putting the RX in a black box and using a very small
lens, thus limiting the amount of total light hitting the surface.  I
may also try using a low-value resitor on my OPT310 RX to widenthe BW
and decrease the gain.  Right now it makes a pretty good oscillator if
you hit it with the laser directly :-)

( and yes, I'm too poor to to afford narrowband filters)

Andy K0SM/2

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