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

[Kerry Banke]

Just as a note - My  simple PSK31 laser transmitter is not linear and 
works well enough.  I basically take the audio output from a laptop 
computer ( or more recently a $6 MP3 player for a beacon)   square up 
the signal and drive the laser  diode full on/off.
  - Kerry -


At 07:14 PM 7/30/2006, you wrote:
>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.