I would expect that a sound card would be stable enough to decode the telemetry signals. All the cards I have seen use a crystal for the reference frequency. As long as the temperature of the card doesn't vary over a wide range you will be ok. The real question is: Is there software avaliable to do the demodulation?

As far as the radio stability is concerned: The signals are transmitted as FM so a slight mistuning of the radio will not affect the frequency of the tones. 

Jim Hannon

---------- Original Message ----------------------------------
From: ian 
Reply-To: psn-l@..............
Date:  Tue, 11 Jul 2006 06:02:30 +0100

>Hi,
>
>thanks for the link.  I wasn't able to deduce from that page how the 
>encoding/decoding works (call me dumb!).  Is there any other web page  
>that would explain it?
>
>I note your comment about stability.  Will your average radio have 
>similar stability or does the encoding method mean that that isn't an issue?
>
>Thanks
>
>Ian
>
>ChrisAtUpw@....... wrote:
>
>> In a message dated 10/07/06, ian@........... writes:
>>
>>> out of interest, what's the spec of how the data is encoded?  I'm 
>>> wondering if a sound card can decode it.
>>
>>
>>
>> Hi Ian,
>>
>>        It is sent as a narrow band sine wave tone. The channel 
>> separation is only 340 Hz. For the center frequencies see 
>> http://psn.quake.net/onlinedocs/demoddoc.html
>> Hence the need for a precision encoder like the XR2206.
>>        Does a sound card to have a stability in the low ppm range? 
>>
>>        Regards,
>>
>>        Chris Chapman
>
>
>
>

--
Jim Hannon
http://www.fmtcs.com/web/jmhannon/
42,11.90N,91,39.26W
WB0TXL
--
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