Hi If you add the +/- 20 ns of sawtooth on top of that you can quickly get some pretty big numbers.
Bob On Sep 13, 2014, at 8:39 PM, Tim Shoppa <[email protected]> wrote: > "Within 15 ns to GPS or UTC (1 Sigma)" means that the 1 sigma spread is > 30ns. > > You have two units and assuming completely uncorrelated errors that would > mean expected 1 sigma spread between them, of 42ns. > > Seeing frequent cases of 80ns delta when the 1 sigma spread is 42ns, should > not be surprising. > > Tim N3QE > > On Sat, Sep 13, 2014 at 6:41 PM, Peter Reilley <[email protected]> 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:[email protected]] 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 <[email protected]> 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. >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
