[Laser] Beginner preamp questions

[Andrew T. Flowers, K0SM]

Steve,

I personally have not experimented with anything but the PGP front end, 
but I have found it to be amazingly sensitive, provided you don't 
saturate the amplifier, which iseasy to do.  I've been working on some 
software for exactly the DSP stuff you are talking about--I can send you 
the "pre-release" java executable if you want.  I am ironing out some 
minor bugs right now and it's about ready for a more public release, I 
think.  For anyone who is interested, I have a notebook of some of my 
laser experiments.  Of course there is nothing "laser specific" about 
it, as it should work great if anyone wants to experiment with LEDs.

http://mail.rochester.edu/~af006m/ , follow the laser link.

Andy K0SM/2

steve kavanagh wrote:

>Well, I couldn't resist buying a couple of C$1.95 1 mW
>laser pointers, so I guess I am going to try this
>stuff ! A photodiode array removed from a junked
>CD-player seems to work OK across the room (MCW, diode
>connected directly to hi-Z headphones).
>
>So an audio preamp is next.  Could anyone comment on
>the pros and cons of
>
>(1) high impedance (e.g. K3PGP) vs transimpedance
>(e.g. WA6EJO) preamps, 
>
>(2) DC coupling of diode to preamp (e.g. K3PGP) vs AC
>coupling using capacitor (e.g. WA6EJO) or transformer
>(e.g. KE4KWR) coupling, and
>
>(3) DC biasing of photodiode vs zero-bias operation ?
>
>I am mostly interested in low data rate weak signal
>work (i.e. MCW or weak signal digital modes),
>including daytime operation.
>
>Steve VE3SMA
>
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