In message <e28a3329130c445db0a3fa4c3ed09...@athlon>, "Ulrich Bangert" writes:
>The true thrill is however one step more subtle: It first considers the >question WHY trimble choose 100 s as the default loop time constant. Well, >this one is easy to answer: Just set the time constant of a "cold" TBOLT to >1000 and watch the TIC value flying to the moon. Expect days before the loop >locks. Trimble NEEDS to set the deafult time constant that low in order to >make the loop of a cold TBOLT lock within a reasonable time. This argument is utttrly bogus: adaptive time-constant PLL's are at least 30 years old, and rather trivial to implement... In NTPns I start out with a timeconstant of about 4 seconds in order to get rapid capture, depending on your timebase, it will increase to several hours (OCXO) or days (Rb). The only "hard" thing about adaptive PLL's is knowing when you have torqued the timeconstant to high, but monitoring frequency of zero-crossing of the residuals (a cheap approximation to a periodogram) solves that easily. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [email protected] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ 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.
