[time-nuts] Navsync CW-12 GPS Board - I don't believe it!!

[Azelio Boriani]

Yes, the error is greater... then maybe the clock of the NCO is not the
chipping rate. In the FTS125 the clock for the RX is sourced by a 20MHz
OFC5DJ3 fixed OCXO but this doesn't imply that the CW12 has a 20MHz
clock... at the moment no other clue comes to mind.

On Wed, Jan 4, 2012 at 5:35 PM, Ed Palmer <ed_palmer at sasktel.net> wrote:

> On 1/4/2012 9:00 AM, Azelio Boriani wrote:
>
>  The output frequency is programmable: try $PRTHS,FRQD,xx.xxx<cr><lf>
>>  where
>> xx.xxx is the desired(?) frequency in MHz with 3 decimal places (they say
>> for 10KHz set 0.010).
>>
>
> Unfortunately, the frequency is programmable only with the NMEA software
> load.  I'm using the Motorola load.  If I reflashed to the NMEA load I'd
> lose the TRAIM functionality.  In any case, the setting doesn't have nearly
> enough resolution to correct such a small error.
>
>
>  Maybe the slight offset is due to the NCO based on the chipping rate of
>> 10.23MHz:
>>
>> 10.23MHz/2^32*4198404003 is 9.99999999783MHz
>>
>
> Your calculation gives an error of 2.17 mHz.  I measured an error of .15
> mHz.  I tried playing with variations on your calculation but couldn't find
> one that fit.  It would be interesting to find out why the error exists,
> but I don't think we will ever know for sure.
>
> Ed
>
>
>
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