[time-nuts] Allan Deviation question

Heinzmann, Stefan (ALC NetworX GmbH) Stefan.Heinzmann at alcnetworx.de
Fri Jul 6 15:52:08 UTC 2012


A few cards accept a reference clock in the MHz range (usually under the term "Superclock"), but most wordclock inputs are made for the wordclock frequency itself, for example 48 kHz. An internal PLL (of varying quality) multiplies that up to a multiple of it for driving the converter and shift clocks.

Those PLLs often have a rather wide lock range, so you'd be able to feed 50 kHz (or 100 kHz or 200 kHz) into it, which can be divided down from 10 MHz quite easily.

Not sure whether that's what you want, however.

Cheers
Stefan


> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] Im
> Auftrag von John Ackermann N8UR
> Gesendet: Freitag, 6. Juli 2012 16:58
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] Allan Deviation question
> 
> I think a number of higher-end sound cards accept a "word clock" or
> "world clock" (I've seen it both ways) that's intended to allow syncing
> to an external source.  The challenge I've seen is that the frequency
> (either in the 12 or 24 MHz range) is one that's not simple to
> synthesize precisely (i.e., zero offset from nominal) and with low
> jitter/phase noise from a 5 or 10 MHz reference.
> 
> I think it would be a great project to come up with a synthesizer block
> that could do that.  It's been on my list for a long time, but hasn't
> yet risen near the top.
> 
> John
> ----
> 
> On 7/6/2012 10:51 AM, Azelio Boriani wrote:
> > Yes, I'm also interested in how-to. At the moment I think it is a
> hack:
> > there is no sound card AFAIK that accepts a reference input. I have
> > recently bought an Acqiris/Agilent DP105/U1067A 150MHz 500Ms/s
> > digitizer PCI card that accepts an external 10MHz as a reference for
> > the sampling process.
> >
> > On Fri, Jul 6, 2012 at 4:43 PM, Stewart Bryant <stewart at g3ysx.org.uk>
> wrote:
> >
> >> ... and running it to a sound card (oscillator gps disciplined)
> >>
> >> How did you achieve this?
> >>
> >> Thanks
> >>
> >> Stewart
> >>
> >>
> >>
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> 
> 
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