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

Ed Palmer ed_palmer at sasktel.net
Wed Jan 4 14:18:41 UTC 2012



On 1/4/2012 2:14 AM, Hal Murray wrote:
>
>> I compared the OCXO output to the 10 MHz output of both a Z3801A and a
>> Tbolt and discovered that the CW-12's 10 MHz output is about 1.5e-11  (i.e.
>> 1.5e-4 Hz) low in frequency.  I emailed Navsync and they replied:
>> "The CW12 Motorola Binary and NMEA versions both do not phase align the
>> frequency output so the long term drift that Ed is seeing is expected."
> Is there a timing version that does the right thing?

Unfortunately, this _is_ the timing version!

>> Incredible.  It's 'steered by the GPS receiver' - that's a direct quote
>> from the data sheet and the user manual - but it's not quite on  frequency
>> and that's fine with them.
> Is it consistently off that much, or does it wander around the right answer?
> (perhaps because there is a small dead band in the phase detector)

The frequency error is consistent.  Superimposed on that error is the 
normal GPS wander that you see with every GPS receiver.

Ed





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