VCF 8.0 Pictures - test-drb@ccmp.vtda.org

11 Nov 2005

  Allison wrote:

...
  RT-11 is an ideal OS for this. 
Just what I thought! :-)

...
    I'd like to see PSK31 software for the -11.

I have not looked into the details of all new digital transmission 
modes that HAMs use (for example with MixW), but without any 
knowledge, I wonder if a PDP-11 would be fast enough ...
any idea about that, Allison ?  

 this is off topic and maybe outof band for this forum:
 The real problem is doing the base band audio processing 
 currently it's done with PCs and sound cards.  The modulation 
 is narrow (200hz or less) band QPSK at around 31 baud or so. 
 The usual reciever is SSB so the challenge is that the audio 
 stream is 500-2500hz bandwidth and multiple converstaions can 
 take place so digital filtering is done to seperate and 
 detect the signals.  Seems to require a P200 or faster. But I 
 haven't dug deep enough.  I have asked one question around 
 but no one has answered and that is what if the reciever 
 (radio) was narrow selectivity (say 300hz) so that only one 
 data stream could be heard, would that simplify the 
 filter/detect/decode process enough for a much slower processor?

 Allison 
Yes, indeed going off topic, but it was sort-of relevant as it
dealt with the possibility in combination with a PDP-11 ... but
thanks Allison. Your last question calls for some investigation.
I hope nobody jumps on this bandwagon, but I guess one brief
reply will not hurt the list. Anyway, it is more on topic
than some recent threads I've seen here ... [pse no flames].
"Close all hailing frequencies, Uhura".

- Henk, PA8PDP.

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