[time-nuts] Correcting jitter on the 1 PPS signal from a GPSreceiver.

[Bob Camp]

Hi

I’m sure they expect you to take out the sawtooth error before you do the comparison. Are you doing that?

Bob

On Sep 13, 2014, at 6:41 PM, Peter Reilley <peter at reilley.com> wrote:

> I see in the Trimble Resolution T data sheet that they
> say that the PPS signal is "within 15 nS to GPS or UTC (1 Sigma) 
> when using an over determined solution in stationary mode.".
> I take this to mean that the PPS signal should be within 15 nS
> and that comparing 2 units that there should be no more than 
> 30 nS between the two edges.   This is comparing the rising edges.
> 
> 
> Pete.
> 
> 
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Bob Camp
> Sent: Saturday, September 13, 2014 6:26 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signal from a
> GPSreceiver.
> 
> Hi
> 
> Where are you getting the "15 ns accuracy" number from? When I look at the
> Trimble spec's they have a number of errors described (like sawtooth) that
> are larger than 15 ns.
> 
> Bob
> 
> On Sep 13, 2014, at 10:41 AM, Peter Reilley <peter at reilley.com> wrote:
> 
>> I have 2 Trimble Resolution T receivers and I have compared the 1 PPS
> signal
>> between the 2 units.   They are spec'ed at 15 nS accuracy.    I am seeing
>> about
>> 80 nS of jitter between the two.   This is with about 6 satellites in
> view.
>> 
>> I was thinking about ways to improve this.   Since this is a stationary
>> installation,
>> can you use the jitter in the reported location (latitude and 
>> longitude) to correct for the 1 PPS jitter?
>> 
>> The location data is derived using the internal GPS disciplined 
>> oscillator so both
>> pieces of information should show the same jitter error.   If you compare
>> the reported
>> location with the known fixed location you should be able to use that 
>> error to correct for the 1 PPS error.
>> 
>> Does this make sense or am I missing something?
>> 
>> Pete.
>> 
>> 
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