[time-nuts] Correcting jitter on the 1 PPS signal fromaGPSreceiver.

Tom Van Baak tvb at LeapSecond.com
Sun Sep 14 11:01:27 EDT 2014


I have not measured the Resolution-T clock frequency. Be aware that the 1PPS timing spec in the data sheet (e.g., N ns from UTC) is not related to the CPU clock frequency.

The CPU clock is directly related to the range of the sawtooth corrections, by the very definition of "quantization". Some receivers use both edges of the clock so you have to be careful about guessing clock rate from sawtooth range alone.

To give you a feel for Resolution-T sawtooth correction here's a histogram:
25,000 sample raw data for the plot:

The standard deviation is 11.7 ns. Depending on how you measure, the range is 36 or 44 ns. Note the mean is about 2 ns (not 0). I'm curious if your Res-T looks the same as mine.

More sawtooth examples:


----- Original Message ----- 
From: "Peter Reilley" <peter at reilley.com>
To: "'Discussion of precise time and frequency measurement'" <time-nuts at febo.com>
Sent: Saturday, September 13, 2014 5:52 PM
Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal fromaGPSreceiver.

>I don't see any mention of sawtooth correction in their documentation.
> I take that to imply that sawtooth correction is not necessary to get 
> the 15 nS that is spec'ed?
> Does the 15 nS imply that the internal clock is 33 MHz?   That is: +-15 nS
> is 30 nS which is 33 MHz.   Is that correct?  Or do they need a higher
> internal
> clock so that all errors sum to less than 15 nS? 
> Pete.

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