[time-nuts] GPSDO unclear situation

paul swed paulswedb at gmail.com
Wed Jan 27 15:28:44 EST 2016


Anton a brief response others will add.
Welcome to time nuts.
Yes the 1pps can be very important to the ultimate stability of the system.
But the fact is many other things come into play.
Poor oscillators sloppy GPS controllers and such can make the 1pps pulse
the least of your concerns.
That said I also have the VE2ZAZ controller it works well and has been
around for most likely 10 years. It was never intended to go to the levels
that some time-nuts can go. Call it a great .1 Hertz solution. Cheap simple
reliable. If thats what you need for Amateur radio work your all set.
But more advanced GPS controllers do all sorts of filtering and averaging
and can deliver stability 3 and more decades in accuracy. Thats when those
better GPS receivers are a need. I have to be careful here because even the
ublox NEO6s can do a pretty good job.

Now comparing all of this to your H maser, well its not really a comparison
and I am unsure what the benefit would be in doing that. I would spend far
more time figuring out how to get a signal from the H maser to my home and
simply forget all the other approaches. Let someone else pay for the power
cooling and maintenance.
Regards
Paul
WB8TSL

On Wed, Jan 27, 2016 at 7:17 AM, Anton Moehammad via time-nuts <
time-nuts at febo.com> wrote:

> Hi All,
> My GPSDO based from VE2ZAZ design but I have a few question I do not
> clearly understand about GPSDO, like :
>  1.How important the quality of 1 PPS signal based from jitter etc what
> the difference I will get between timing purpose GPS module like Ublox 6T
> or trimble resolution T with a position GPS module like ublox 6M or other
> in term of stability, accuracy and phase noise.
>  2. I understand short time stability from OCXO is better than GPSDO ? can
> someone give me a clue what the time constant need for OCXO control (in my
> application 30 second) is that enough ?
> 3. I have few Rubidium oscillator and I read somewhere (I believe in KE5FX
> web) that GPSDO with rubidium osc is hard to beat, in what way ? short
> time, long time, phase noise.
> My goal is "simple" I have access to national time reference lab ( an
> active Maser H ) I want to compare my reference to them off course there is
> no way I have same stability but anything not so "embrace" is fine to me
> Thank you for all opinion/advice.
> Anton Hendra
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