[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
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