Hi The ~ +/- 40 ns correction takes you down to a residual error in the ~+/-10 to +/-20 ns range. Using it is an improvement, but it's not day and night.
Bob On Feb 18, 2010, at 12:02 AM, Don Mimlitch wrote: > I have been working with a HP58534A GPS Timing Antenna which outputs extended > NMEA sentences including a custom sentence which specifies the Timing Error > of the NEXT 1PPS Pulse as a number between +00 and +85 Nanoseconds. I am > wondering whether using a PIC to correct each 1PPS pulse using this sentence > would be worthwhile to clean up the saw tooth in the 1PPS and if so what > would be the best way to correct each 1PPS. > > One solution might be to send the receiver the custom NMEA sentence which > lets me set the antenna delay +/-nnnnnn Nanoseconds. I would use the timing > error plus the actual cable delay to calculate the nanosecond delay to use > for the next pulse and send the cable delay sentence to the receiver before > the next 1PPS pulse. I have at least 100ms to send this message at 9600 baud > before the specified pulse arrives. This should be sufficient time assuming > the receiver acts on the message immediately. > > A second approach would be to use a programmable delay line (about $14 from > jameco) to correct the the 1PPS by 85ns - Timing Error from message. I would > set the cable delay to 85ns more then the actual cable delay to bring the > 85ns in the delay line calculation. > > I'm sure all the timenuts will have better or simpler solutions to this > concept and many different views on whether it is worthwhile to do. > > > > > _______________________________________________ > 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.
