I have spent another evening playing around with the 5370 and the conclusion is pretty ironclad now:
Running a 5370 with ext-ref locked to input frequencies is simply a bad idea and should not be done. Running it on the internal OCXO works fine. Running it on another frequency *not* locked to the input frequenc also works fine. In both cases the errors are statistically well-behaved, and can be treated with normal statistical methods, including the built-in STD-DEV function. But feeding ext-ref a frequency which is locked to the input frequencies causes the errors to become systematic, and they can no longer be treated as statistically well-behaved. For instance: The length of the coax to ext-ref suddenly affect your TI measurements, because it shifts the phase between the 200MHz and the input signal. I tried tuning up the A21 200MHz synthesizer to the best of my ability, and it clearly made a difference, the phase pattern of errors shifted around, but the errors did not get any smaller, they just moved. I also tried disconnecting the "10 MHz present" circuit, that didn't change the magnitude of the errors either, but did shift the phase of the peak noise a couple of degrees. Looking at some old notes from years past which just didn't make sense, does now. -- 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.
