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.
