[time-nuts] UBlox as a reference clock source - accuracy ??

[Bob kb8tq]

Hi

The other gotcha is that (as noted in other posts) the signal is not particularly clean noise wise. 
Given the low cost of a GPSDO these days, going that way is not a really big deal investment 
wise. Even the low end units will give you a *much* better 10 MHz to drive an instrument than 
the raw output from a GPS module.

Bob

> On Jun 20, 2019, at 7:20 AM, David Slipper <softfoot at hotmail.com> wrote:
> 
> That is probably good enough for my needs and certainly better than the cheap XOs in the instruments.
> 
> BTW I just came across a document "GPS-based Timing Considerations with u-blox 6 GPS receivers - Application Note" that makes interesting reading.
> 
> Many thanks
> Dave
> 
> 
> On 20/06/2019 00:19, Bob kb8tq wrote:
> 
> Hi
> 
> On a second to second basis, the 10 MHz will be off by < +/- 0.02 ppm.
> Averaged over 24 hours ( = your frequency counter is set to a > 80,0000 second
> gate time) you will be much closer. +/- 0.0000001 ppm is a good guess.
> 
> The important point is that the first number is more often the one you bump into.
> The second one only “counts” if you have some sort of flywheel that does the
> 
> 
> 80,000 second averaging for you.
> 
> 
> 
> Bob
> 
> 
> 
> On Jun 19, 2019, at 4:31 PM, David Slipper <softfoot at hotmail.com><mailto:softfoot at hotmail.com> wrote:
> 
> 
> Hi, I am running a UBlox Neo-6M and have configured it with LadyHeather
> to produce a 10MHz output for use as a better reference for a couple of
> instruments.
> 
> Is there any way with LH to determine the accuracy of the 10MHz output
> in ppm??
> 
> I am aware that the 10MHz output is jittery on my scope (is that phase
> noise??) due to the fact that the internal clock is divided by a
> non-integral value to reach 10 (I believe the internal oscillator is
> 16MHz).  If I set it to produce 8MHz it is rock solid.
> 
> I am really interested in the long term accuracy of the 10MHz signal -
> say over 24 hours.
> 
> I'm a bit of a newbie at this so any clarification would be welcome.
> 
> TIA Dave
> 
> 
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