[time-nuts] Motorola M12+T - On board oscillator phase noise specand/or part number

Stephan Sandenbergh stephan at rrsg.ee.uct.ac.za
Thu Jan 8 15:01:54 UTC 2009


Hi Tom,

Thanks - the data is rather useful. Do you perhaps know what the high freq
phase noise looks like?  I'd like to lock the GPS LO to the output of my
GPSDO. However, the integrated jitter will probably determine if it could be
done, by something as simple as filtering the output of a fractional N
(implemented inside a FPGA) or maybe a dedicated fractional N IC with
low-noise VCO (such as those from Analog Devices). I guess the latter is
more realistic.

I'd guess the stock TCXO onboard the M12+T would have a noise floor below
say -140dBc/Hz.

Regards,

Stephan.

2009/1/2 Tom Van Baak <tvb at leapsecond.com>

> > Hi All,
> >
> > Has anyone been able to figure out the part number and/or measured the
> > phase noise of the quartz oscillator on board the Motorola M12+T?
> >
> > This will be an interesting figure to see.
> >
> > Regards,
> >
> > Stephan.
>
> This is an ADEV+MDEV plot for the 100 Hz output of an
> M12+ in free-run mode (no gps lock).
>
> http://www.leapsecond.com/pages/m12-adev/m12-free.gif
>
> If you want more data let me know.
>
> /tvb
>
>
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