[Laser] more strobelight stuff

[Tim Toast]

Here is some more info about this and keep in 
mind this is just in the planning stages and 
evolving a bit. I made a block diagram today 
of some possible systems: 
http://aladal.net/toast/xbpsk.gif

I'm tending to go with the idea of using the 
audio output from the computer software now 
instead of trying to generate part of the psk 
signal.

In the case of BPSK, it needs to be demodulated 
partially first in order to get the raw digital 
"control waveform", unless it's already available 
from the software. Then that is used to drive a 
one-shot multivibrator that has a suitable width 
output pulse. The output of the one-shot is used 
to drive the strobe trigger circuit which will 
in turn make the high voltage pulses to trigger 
the strobe. 

Some problems with this:
I'm not clear right off hand how to demodulate a 
PSK signal partially or whether the one-shot needs 
to produce a pulse on both low-high and high-low 
transitions. Also i was thinking with a "baseband" 
psk31 signal, the output of the one-shot will be 
31.25~Hz? If thats true then the strobe is only 
going to fire at that rate... and that would 
probably be a problem on the receive end when 
trying to use it with existing PSK software. But 
maybe it can be driven somehow from a higher 
frequency carrier in the 80-90 Hz range or above 
the 120 Hz buzz ..but not too far above. 
loose edges. Any thoughts on this?

On the other hand, using the LaserScatter audio 
seems a bit easier. You would only need to "limit" 
the signal to square it up and condition it for 
the one-shot (if it's a sinewave). The one-shot 
triggers on one of the transitions - low-high or 
high-low of the input. As long as the input 
frequency remains the same, the trigger pulses 
will be created at that rate. Then when the 
frequency changes to the next character, the 
trigger pulses follow along in step at the new 
rate. And if this is all in the range of 10-30 Hz 
or so, then no problems for firing the strobe at 
those rates. 
This seems like it should work and i'm leaning 
towards it for now although i'd like to get the 
psk kinks worked out as well somehow. 
Any feedback is appreciated.


=====
Tim Toast
http://www.aladal.net/toast/

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