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

Brian Kirby kilodelta4foxmike at gmail.com
Mon Jun 1 23:07:13 EDT 2009


I use a Lynx One sound card, it has analog and digital I/O and MIDI I/O 
and clock I/O.  Their manuals are available on line at 
www.lynxstudio.com.  These are profession 24 bit cards, the analog I/O 
uses balanced interfaces.  They handle AES/EBU and SP DIF digital audio 
formats.

The sound card can take an internal clock, an external clock input on 
the MIDI port, there is a parallel clock header on the PC board, and a 
digital clock input on the digital audio lines.

It can accept a 13.5 Mhz video dot clock, a 27 Mhz video dot clock, and 
a word clock and word clock/256.

It can also take a single source frequency as a referenve clock.

Its basicaly set up to sync and slave SMPTE timing systems

Hope that helped......

Rex Moncur wrote:
>  
> Hi all 
>
> Does anyone have any experience of locking a USB external soundcard to a
> GPSDO 10 MHz reference.
>
> I am interested in advice on any good quality soundcards that can be readily
> locked to either 10 MHz or if necessary to some other frequency that we can
> derive from a GPSDO source.  I have done some tests with the SignalLink
> soundcard that uses a Texas Instruments PCM2904 chip and requires a 12 MHz
> lock frequency.  This requires some cutting of tracks to remove the internal
> oscillator feedback and insert the locking frequency.  12 MHz is readily
> derived from 10 MHz but I have not been able to get it to lock.  The Texas
> instruments data sheet suggests that it is possible to use an external
> refernce but also says this is not recommended.  With this expereicne I
> would rather find a sound card that is designed for external locking that
> does not require the cutting of tracks.
>
> For info the purpose of this request is that we are looking at using very
> narrow bandwidth modes at less than 1 mHz for light wave communcation.  To
> date using LEDs and cloud reflection we have worked over 200 km with WSJT
> but we should be able to do 20 dB better if we can get down to milli-Hz
> bandwidths (at the expense of spending all night to complete a QSO). Our
> expereince to date is that standard sound cards are just not stable to
> better than 5 milli-Hz at 1000 Hz which should be readily solved by GPS
> locking let us get down to sub milli-Hz levels.
>
> Rex VK7MO
>
>
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