The gold standard is a random pulse source. Using something like a SPAD as the source of random pulses is popular as the average rate can be easily adjusted by changing the light level. It also avoids using radioactive sources.
Bruce > On 03 April 2017 at 15:05 Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > > > For even more fun you could try to detect the PTFE phase change at around > 20C using a cable with PTFE dielectric. > > A pulse source with somewhat more pulse to pulse jitter may be more useful in > that averaging will occur over a wider range of fine interpolator codes. > > Bruce > > > > > On 03 April 2017 at 05:34 Mark Sims <hol...@hotmail.com> wrote: > > > > I implemented the channel offset compensation feature specifically to > > make measuring cable delays more accurate. I wanted to measure my TDR > > calibration cable and another very precision delay line. I used Heather to > > null out the channel/connector delays and then replaced one of the "T" > > cables with the TDR cable. > > > > My test setup / TICC was coming up with a -306 ps channel offset error. > > The test signal was the 1PPS output of a FTS4060 cesium. Connecting / > > reconnecting one of the test setup cables and re-doing the offset test (I > > was averaging for 1800 seconds) could produce compensation values that > > varied from -300 ps to -325 ps. Just de-doing the offset test without > > messing with the cables produced values around -300 to -310 ps. > > > > BNC connectors aren't the best for precision timing. I need to re-run > > the test with SMA cables / T adapter and the precision HP connector torque > > wrench and see what that looks like. It would also be fun to lay a coax > > outdoors and see how the delay changes over a day as it heats/cools. > > > > -------------------- > > > > > > > > > Some “cables” have very long delay numbers. > > > > > > _______________________________________________ > > > time-nuts mailing list -- time-nuts@febo.com > > > To unsubscribe, go to > > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
