[Laser] Stepper motor control of laser communication unit

[Kerry Banke]

Andy - I just figured I'd have a switch on the laser to turn it off if 
necessary. My experience so far is that my  collimated laser or LED beam 
has a tremendous amount of backscatter if the Tx & Rx units are co-located 
& pointed parallel to each other. I should just be able to turn off the 
laser power at one end to do simplex shouldn't I? I guess an output from a 
port on the computer could be used to turn on/off  Laser  power eventually 
if needed.
  -Kerry -

At 12:00 PM 10/22/2004, you wrote:
>Kerry,
>
>I don't have a simplex option in the SW, but I suppose I could make 
>one.  As long as you don't drive your soundcard into clipping it should be 
>okay.  You need to set one station to transmit on the "top" band and the 
>other on the "bottom" band.  The only QRM you will get from your own 
>signal will be spectral bleeding from your own signal several bins 
>away.  If this is a problem you might try the "Blackmann" window function 
>as it is designed to attenuate the bleeding into bins removed from the 
>signal.  A good way to test is to try transceiving in full duplex ((TX 
>high, RX low) with one station and seeing if you get a significant amount 
>of energy filling up the receive band.
>
>Even if your own signal is way above the noise floor you shouldn't have 
>any trouble resolving much weaker signals at other frequencies.  A 
>computer FFT has much longer integration time than our ears and thus 
>better frequency resolution.  For example, we can't separate two CW 
>stations 20Hz apart by ear, but we can see it fine on a spectrogram.
>
>Andy
>
>Kerry Banke wrote: