Hi The nice thing about a spool of coax is that it's got a bit of thermal mass. It will average out a lot of minor temperature ups and downs.
Bob On Dec 17, 2012, at 4:34 PM, Hal Murray <[email protected]> wrote: > > [email protected] said: >> If you are trying to set up say a 1 us delay, you will get ~ 50 ps per >> degree C in your delay. That's a lot ..... > > A while ago, [email protected] said: >> A long delay cable is fine too. If these are timing receivers you probably >> don't need more than 100 ns of delay, once you figure out which receiver is >> ahead of the other. The cable tempco is low enough not to worry about. > > 100 ns is 50-100 feet. That's a reasonable length to work with. But I was > curious about the temperature coefficient. Google found this: > http://www.hepl.hiroshima-u.ac.jp/phx/notes/cable/cable.html > which says: > # Belden 8240 (solid) shows a temperature coefficient of around > -0.252ps/m/deg in a temperature range between -20 and 30 deg. The coefficient > becomes steeper beyond 30 deg. > # Belden 8219 (foam) shows a larger temperature coefficient of around -0.352 > ps/m/deg than that of 8240 in the similar temperature range. The coefficient > becomes steeper beyond 30 deg, but less steeper than that of 8240. > # Fujikura RG58-A/U shows the smallest temperature coefficient of around > -0.152 ps/m/deg, but in a narrow temperature range between -10 and 20 deg. > The coefficient beyond 20 deg is much steeper than the others. > > To pick round numbers, 30 meters and 3 C and 0.25 ps/m/C gives 25 ps. > > > -- > These are my opinions. I hate spam. > > > > > _______________________________________________ > 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. _______________________________________________ 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.
