[ntp:questions] Re: wwv audio testing

David L. Mills mills at udel.edu
Sun Jul 30 16:40:32 UTC 2006


The tool works for IRIG, too. The problem with the WWV generator is that 
there is no feedback loop correcting for the audio codec intrinsic 
frequency error. The only way to do this is looping the soundcard output 
to input and disciplining the generator to the system clock as 
maintained by NTP. Not really hard, but intricate.


rtxo wrote:
> Hi Folks---
> If you've been trying to get the ntp audio code working, its handy to 
> have a
> known source of audio available. There's a tool in the ntp distribution 
> that
> works on solaris (I've tried it under solaris x86) to do this. No port for
> linux or freebsd, yet, though, that I've seen.
> This afternoon I managed to get Colin Plum's wwv hack working ok under 
> linux.
> I fixed a few bugs, and now it seems to happily generate a wwv signal 
> out the
> sound card of my linux alsa setup. Feeding this into another linux host 
> that
> is running the ntp audio code works nicely. The sending computer is 
> locked to
> GPS via ntp, and the little audio tool ticks along just swell.
> I've added a paragraph about this on my PC gnu/linux and freebsd ntp 
> server page:
> http://www.wraith.sf.ca.us/ntp/index.html#test-tones
> There's a link to the patched code on the site.
> If your audio setup works with this, then you should be able to get the 
> or CHU audio going as well. I've configured up IRIG here, but I don't have
> a radio that is CHU capable so I haven't done that yet.
> The sound card part is still a bit tricky. Audio input seems to not 
> always be well
> tested in the drivers.
> ../Steven

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