Another question, a bit off the road of this thread: Is there any common practice for the duty cycle of the 1 PPS pulse? I have seen devices having extremely short 1 PPS pulses with duty cycles of a few percent or less and others with close to 50% duty cycle.
Best regards Bernd DK1AG -----Ursprüngliche Nachricht----- Von: time-nuts [mailto:[email protected]] Im Auftrag von Bob kb8tq Gesendet: Dienstag, 14. August 2018 17:05 An: Discussion of precise time and frequency measurement <[email protected]> Betreff: Re: [time-nuts] 1PPS for the beginner Hi > On Aug 14, 2018, at 10:33 AM, Ron Bean <[email protected]> wrote: > >> A normal GPS module generates it \200\231s outputs off of a free >> running internal clock. Generally this is a TCXO in a >> \200\234timing \200\235 GPS ( = one that puts out a rational PPS). >> This i bit counter intuitive, since you would *think* they phase lock >> the local source in the module. They don \200\231t mainly because it >> makes the math easier. > > Is there a need to make the math easier? > This is what we have microprocessors for. There is *always* a need to make the math easier if I’m quickly typing up an example. For proof I reference the hundreds of posts in the archives where I didn’t quite get it right :) Indeed, the real numbers could be just about anything. They are highly dependent on what’s in the specific module. In some cases, the clock involved is well over 300 MHz. Bob > > Thanks for the "hanging bridge" explanation. It would be nice if > someone had a time-nuts-glossary that included various terms that come > up on the list, like "hanging bridge", "spurs", "sawtooth correction", > "GPS allan ski jump", etc. > > Is there a time-nuts FAQ? > > > _______________________________________________ > time-nuts mailing list -- [email protected] To unsubscribe, go > to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
