[Laser] One way 3 mile laser NLOS contact using PSK31

[KY1K]

>
>
>Wouldn't .0001Hz resolution require something on the order of 1 ppm at 
>100Hz?  Do you need a TCXO in your soundcard?

.0001 Hz is actually 100 ppm, unless I did may math wrong. It should be 
attainable easily with computer grade quartz crystals. I think 10 ppm ( 
.000001 Hz ) should be ok too, but much beyond that will probably become 
more of a technical challenge.

There are high accuracy modules made for some soundcards now, and there 
have always been tcxo timebases for computer clocks that plug in and are 
easily available. Interfacing a high stability oscillator to a soundcard 
enables very serious narrowband bins.

Of course, you will need the inverse of the minimum bin width before the 
signal can be detected, so .001 Hz bins means you have to look at 1000 
seconds worth of data before you can determine whether you are hearing the 
desired signal. Since 1000 seconds is 15+ minutes per bit, so it is 
probably the practical limit for amateur laser experimenter use. But, bins 
at .0001 hz each should be attainable with computer grade quartz crystals 
on stock soundcards.


>(Three days to vacation.....)

Enjoy the vacation Andy.

Art

PS:Has anyone ever evaluated the sensitivity of a PGP front end compared to 
an OPT-301 or OPT-210 based front end? This should be fairly easy to do 
with spectrum lab as long as the illumination is corrected to compensate 
for the relative difference in the active area of each units photodiode.