[time-nuts] Cheap 9.8Mhz Sa.22c's

[David McGaw]

I bought one a while ago and have been in contact with Symmetricom. The 
data sheet is confusing.  These do indeed have a 58.9824 MHz oscillator 
and CANNOT be changed to 10 MHz.  They can be changed to divide by N >= 
2 to include 29.4912 MHz, 9.8304 MHz, and even 32.768 kHz if you wish, 
as has been said, to have a very accurate watch or RTC.

They do NOT include the PPS disciplining function.  The PPS output can 
be enabled, but I have not figured out a good way to synchronize it.  
PPS output does not change when the divide by N is changed.

The analog and digital frequency controls can be enabled and are functional.

A AD9851 DDS fed 29.4912 MHz and set to multiply by 6 could give 
10.000000003051758 MHz, off by ~3 E-10, well within the range of the 
digital control.

73,

David


On 6/2/13 5:19 PM, Tom Miller wrote:
>
> ----- Original Message ----- From: "Chris Albertson" 
> <albertson.chris at gmail.com>
> To: "Discussion of precise time and frequency measurement" 
> <time-nuts at febo.com>
> Sent: Sunday, June 02, 2013 3:16 PM
> Subject: Re: [time-nuts] Cheap 9.8Mhz Sa.22c's
>
>
> What are you planning to do with the 10MHz signal.   In some cases you 
> can
> simply use 9.8304MHz.  For example my plan to drive a DDS chip. Nominally
> the DDS wants 125MHz but iif I put in some odd-ball thing like 
> 119.6MHZ all
> that means is I have to change the binary word I load into the DDS chip.
>
> In fact that could work.  Use the 9.8305 to drie a DDS then have the DDS
> synthesize what you really want.  It will be as stable as the Rb. but as
> accurate as 1/2 the step size of the DDS.
>
> -
>
> And then you can make the fine frequency adjustments to the Rb 9.8 MHz 
> in software.
>
> Regards,
> Tom
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