{Collins} Re: PSK 31



Hi John,

I put my S-Line (75S-3B and 32S-3) on PSK31 a couple months ago. I used the 
DigiPan software, and my computer was a standard Dell Inspiron 600m, with 
nothing special in the way of a sound card. I constructed a microphone cable 
and a headphone cable to connect to the laptop audio I/O connectors. Inside 
each of the new cable jacks, I constructed suitable attenuator pads to 
create suitable audio levels. I also constructed a simple FET circuit that 
would automatically key the S-Line PTT line from the computer. All this 
worked quite well.

The only problem I had involved the fact that stations you contact expect 
you to be within perhaps 10Hz of their frequency. The DigiPan software locks 
onto the station you are receiving, and generates an audio output 
corresponding to that received audio tone. This works great for most modern 
transceivers, but when using the S-Line (in transceive mode) only two of the 
three conversion oscillators are shared. The audio-to-455kHz oscillators 
(BFO) are not shared. Unless you are incredibly lucky to have BFO crystals 
in your receiver and transmitter that are very closely matched, your 
transmitted audio will have an offset from your received audio. Mine were 
off by around 40Hz, and as I tried to work a station, we continually stepped 
down the band as he tried to follow me. After I figured out what was going 
on, I found that I could turn the 75S-3B variable BFO on, and carefully 
adjust it to match the 32S-3 oscillator. This is a little tricky, but you 
can do it with a little practice using DigiPan.

It seems that there should be a way to tell the software that there is a 
known frequency offset between the upconversion and downconversion paths, 
and let you crank in a correction. DigiPan has something that looks like 
that, but it doesn't work in the way it needs to in order to fix this 
problem. Maybe some other software does have this feature. I am really just 
a novice on PSK31, so if anyone knows of software that can handle this 
"frequency offset correction" problem, I would like to know about it.

Another approach would be to insert an inductor (variable) in series with 
the 75S-3B BFO crystal to pull it close in frequency to the corresponding 
32S-3 BFO. I really would not want to do this, however. Handling it with 
computer software would be much preferable.

Good luck,
Don
W5QN




----- Original Message ----- 
From: "John & Carmen Deithloff" <john@xxxxxxxxxxxxx>
To: "Collins Reflector List Server" <COLLINS@xxxxxxxxxxxxx>
Sent: Thursday, June 14, 2007 7:03 PM
Subject: {Collins} PSK 31


> Hello to the CCA List.
> Has anyone used their Collins Radios with appropriate equipment for PSK 
> 31?
>
> What other equipment was used? New sound card? Tigertronics sound card?
>
> If so, what were the results? Difficulties?
>
> Thanks,
> John, W5FFS
> CCA 01305
>
> John & Carmen Deithloff
>
>
>
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.
SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY !
      http://www.collinsradio.org/html/membership.html    -paypal accepted-
.
 NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
  SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200 Central
       1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT)





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