-------- In message <[email protected]>, Tom Van Baak writes:
>The plot is beautiful. The reason this delay line technique isn't used >much anymore is that AFAIK the Dallas chips are no longer produced. So >almost every uses s/w sawtooth correction now. So... this is where it gets complicated isn't it ? If you saw-tooth compensate the PPS in hardware, and then use it to latch some digital counter, you may actually have made your performance worse, because you lost the "dithering" of the counter provided by the sawtooth, and all else being equal, just created a new "hanging bridge" problem. If instead you latch your counter on the uncompensated PPS and apply the saw-tooth compensation in software, you most likely dither the +/-1 count noise almost out of existence. Compensating the saw-tooth in hardware only[1] makes sense (IMO) if you feed the compensate PPS into an analog PLL and want to reduce the "hanging bridge" effect to the resolution of your delay-line. And if you implement an analog PLL in time-nuts territory where the timeconstants are measured in minutes and hours, you have far bigger challenges than the hanging bridge from the GPS... [1] Or, I guess, if you want to feed the PPS to your HP5370 without having to postprocess the TI measurements for the sawtooth. -- 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 http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
