[time-nuts] Some GPS performance plots
brooke at pacific.net
Wed Nov 3 12:46:32 EST 2004
Years ago I tested the Oncore VP+ and found the sawtooth had glitches.
But I did make the correction two ways.
The software approach was to measure the time interval via HP-IB and the
saw tooth via RS-232, then use the PC to apply the sawtooth prior to
plotting or recording the data.
The hardware approach was to use a PIC to read the sawtooth value and
then program a digital delay chip placed in line with the 1 PPS output.
As far as I can remember the chips came with 1 or 1/2 nanosecond steps
and by starting half way you could get positive or negative sawtooth
But they both caused poorer results with the VP+ because there was a bug
in the sawtooth data.
Brooke Clarke, N6GCE
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
John R. Ackermann N8UR wrote:
> Nothing sexy here, but in response to some serious confusion on the
> NTP mailing list, I put together some plots of the 1pps output from a
> Motorola M12+ Timing Oncore versus an Rb standard. It may be helpful
> if you want to point people to info about GPS timing capabilities.
> (Some folks on comp.protocols.ntp were busy lawyering the Motorola
> manual and getting really screwed up about the accuracy -- or lack
> thereof -- of the 1pps signal.)
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