[time-nuts] GPS 1PPS ultimate accuracy

Andrea Baldoni erm1eaae7 at ermione.com
Thu Jan 15 04:56:56 EST 2015

On Mon, Jan 12, 2015 at 06:16:01PM -0500, Bob Camp wrote:

> Actually it’s a bit worse than you might expect. 
> The uncorrected sawtooth will give you about 20 ns of wander. At the one day
> level, GPS without some sort of ionosphere help (like a dual frequency
> receiver) will add another 10 ns or so to that. Net, your pps is spread over
> a 30 ns range. 

Hello Bob.
Thank you, now I have a better idea.
I understand that the NTP is completely ruled out and also between GPS there
is a strong difference.

> With things like 5335’s running around for cheap prices, I would suggest
> doing this with a counter. You are going to spend a lot of days getting very
> much data. Your time’s got to be worth something …. 

Actually I own a Racal 1995 that should be better than the 5335 with its 1ns
single shot resolution.
However, I don't still own a GPSDO to reference the counter so how do you
suggest to use it?
I should use total A over B with the DUT in A and the PPS in B?

Best regards,
Andrea Baldoni

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