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

Ed Palmer ed_palmer at sasktel.net
Wed Jan 4 16:35:18 UTC 2012


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




More information about the time-nuts mailing list