[Laser] PSK31 via light - up-convert to RF vs audio amp

[riese-k3djc at juno.com]

On Sun, 30 Jul 2006 22:14:03 EDT TWOSIG at aol.com writes:
> I was thinking about how to set up a PSK31 demonstration over a light 
>  beam.  
> Since PSK31 is a very linear modulation mode, primarily for narrow  
> bandwidth 
> that is not of primary concern to a light beam channel, it may be  
> easier to 
> impliment with LED than with laser.  The circuit that I use for  AM 
> with LEDs 
> should be able to take the audio output from a sound card as well  
> as from a 
> microphone.  I am not happy with the receive system that I  use with 
> the AM 
> demo, the receiver from Ramsey pulse width modulation laser  system. 
>  It uses a 
> phototransistor as the sensor, and I do not consider it  easy to 
> build, unless 
> you buy the Ramsey kit, or to modify for different  needs.
>  
> I thought of building a pre-amp, such as the K3PGP design,


I havent looked at it for some time but as I recall I used a phono
connector at the input to the ramsey rcv. 
Then I could plug in the ramsey photodoide or the PGP front end or
anything else

The PGP front end worked well and really upped the sensivitity

Bob K3DJC