[time-nuts] 1PPS correction from HP58534A GPS Timing Antenna
Ulrich Bangert
df6jb at ulrich-bangert.de
Thu Feb 18 08:00:17 UTC 2010
Don,
> One solution might be to send the receiver the custom NMEA
> sentence which lets me set the antenna delay +/-nnnnnn
> Nanoseconds.
If something like this were possible, the receiver would do it for himself
(if called for)!
> 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.
Yes! Has already been done, for example here:
http://www.cnssys.com/cnsclock/CNSClockII.php
In my DIY GPSDO I do it in the software.
Best regards
Ulrich Bangert
> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Don Mimlitch
> Gesendet: Donnerstag, 18. Februar 2010 06:02
> An: time-nuts
> Betreff: [time-nuts] 1PPS correction from HP58534A GPS Timing Antenna
>
>
> 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.
>
>
>
>
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