Re: [gpsd-users] Enable PPS Echo

[Greg Troxel]

Reto Zbinden ST <address@hidden> writes:

> But if the time is compared to some reliable public stratum 1 servers
> (e.g. metas.ch), it seems that the local clock is always a few
> milliseconds behind these servers. I'd like to do some more precise
> measurement to figure out the latency of the 1PPS signal processing
> and to adjust the fudge time. According to what I've read, the delay
> can be measured using an oscilloscope and the PPS echo feature. But I
> couldn't figure out how the echo function can be activated.

I'll second all the other comments.

Another thing you can do is get a few more models of GPS receiver with
PPS, and a few more computers, and hook up one GPSr to each computer,
and compare them across the LAN.  Of course, you can't really conclude
that PPS is off from this, but if you see really close agreement (sub
ms, and maybe even 100 us), that's a clue that each of your local
GPSr/PPS setups is ok.

Of course, having one GPSr for timing is normal, two not so wierd, three
a bit funny, and soon after that you're that crazy guy with too many GPS
receivers that everybody crosses the street to avoid :-)

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