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

SAIDJACK at aol.com SAIDJACK at aol.com
Wed Jan 4 21:08:37 UTC 2012


Hi Ed,
 
sorry to hear that, contact me off-list and I will try to solve your  
problem. I tried sending you an email, but my mails must be getting filtered by  
your spam filter..
 
bye,
Said
 
 
In a message dated 1/4/2012 11:33:14 Pacific Standard Time,  
ed_palmer at sasktel.net writes:

On  1/4/2012 11:13 AM, Said Jackson 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?

Yes, it does.  Cooling the unit by using a heatsink  causes a significant 
increase in the output frequency.  The change is  large enough to be 
obvious on an oscilloscope where one channel is the 10  MHz from the 
Z3801A and the other channel is the 10 MHz from the  CW12.

> 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..

Yes, it appears that the CW12 is just not appropriate for  what I was 
thinking of doing.  However, to be fair, the 1 PPS output  is much better 
than the older receivers.  I'll have to think about  where I go from  here.

Ed


_______________________________________________
time-nuts  mailing list -- time-nuts at febo.com
To unsubscribe, go to  
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the  instructions there.



More information about the time-nuts mailing list