Interesting...now i wonder how they can steer the frequency. Usually in C/A GPS receivers the oscillator is not corrected and any drift is accounted for in software: usually you see geographic coordinates out of the receiver. In the Motorola receiver they say the PPS has the granularity of the oscillator (and the negative sawtooth can be used to compensate and obtain greater precision) so no oscillator correction is necessary either: just place the rise of the PPS at the nearest clock transition (and the residual went in the previous sawtooh). Now to correct the frequency output of a CW12 without adjusting the clock the only way is to change the phase accumulator step: maybe the phase accumulator in the CW12 is greater than 32bit...
On Wed, Jan 4, 2012 at 6:13 PM, Said Jackson <saidj...@aol.com> wrote: > Hi Ed, > > Since the oscillator is typically free-running in an NCO, and periodically > corrected by phase drops to stay "on frequency" the error you are seeing > may be caused be the offset in your crystal, combined with the limited > digital resolution of the NCO trying to correct for this offset. > > If this is the case, your measured error would change with temperature. > > Does it do that? > > If yes, the NCO resolution is not fractionally corrected all the way. > Replacing the on board Tcxo with an ocxo hand-tuned to the correct > frequency would help, but that sort of defeats the purpose of the product.. > > Bye, > Said > > Sent from my iPad > > On Jan 4, 2012, at 7:05, Ed Palmer <ed_pal...@sasktel.net> wrote: > > > On 1/4/2012 8:49 AM, Mike S wrote: > >> On 1/4/2012 9:29 AM, Ed Palmer wrote: > >> > >>> What's the point of saying that it's "steered by GPS" when it's > >>> off-frequency. What does that even mean? Does it steer the frequency to > >>> keep the error constant? > >> > >> If it's constant, maybe they just need to re-spec it as having a > 9.99999999985 MHz output. :-) > >> > > > > Ooohhhh, it's a GPS steered offset generator! Now I get it! :-) > > > > Ed > > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.