[time-nuts] Re: gpsdo by leo bodnar & picdiv

[Jürgen Appel]

Hej,

On Monday, 25 November 2024 15:47:14 Central European Standard Time Brian 
Lloyd via time-nuts wrote:

> I have the units you mention, plus the newer one, which is what you really
> want. Neither of your devices will produce a 1pps output. They are strictly
> frequency references, not time references, and have a minimum frequency of
> about 400Hz.

I'd like to underline this. The phase of the generated frequency is not locked 
to the 1pps from the internal GPS module, i.e. although they deliver an output 
frequency with an accuracy within their specs, there is a remaining frequency 
offset that does not average out to zero, and any clock you build with them 
will drift, even with GPS lock.

I contacted the manufacturer and got a modified firmware, such that that is 
solved at the expense of additional noise from 1s to 2000s avering times. 
Using the output with this modified firmware to generate your own 1 pps will 
keep time on a long timescale - although you still would need a way to find 
the correct offset from UTC to make it a usable clock.


Cheers,
	Jürgen


-- 
Jürgen Appel
Senior Scientist
Denmark's National Metrology Institute
Dansk Fundamental Metrologi, DFM A/S (dfm.dk)
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DK-2970 Hørsholm
Denmark

Mobile: +45 25459049
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