[time-nuts] Sound Cards for locking to GPSDO 10 MHz references

Magnus Danielson magnus at rubidium.dyndns.org
Tue Jun 2 15:31:17 EDT 2009


Alberto di Bene skrev:
> J.D. Bakker wrote:
>> You could always transform this from a hardware problem to a software 
>> problem. Take the output of your GPSDO, divide it down to somewhere 
>> inside the audio band, feed it to a spare input on your USB sound card 
>> and have software track this reference and correct the received signal.
>>
>> JDB.
> 
> I am in complete agreement with this kind of solution. Sampling on the
> second channel a reference signal of known value allows the software
> to make a simple adjustment.

Such a double-frequency conversion cancels fairly well the transfer 
oscillators frequency and jitter, as long as it is sufficienly low.

> No need to switch on the soldering iron...
> Never do in hardware what can be done in software.... :-)

Respectfully I disagree. There are tasks which is better managed by 
software and tasks which is better managed by hardware. In the world of 
FPGAs, it is also worth mentioning that some tasks is best done there.
The big trick is to find a balance between various methods, available 
resources, partitioning of the problem, doing it on time and achieving 
the needed performance.

There is an overbeleif in what software is suitable for IMHO.

Cheers,
Magnus




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