I wish there was an source for helically wound shielded differential transmission line like the type used in later analog oscilloscopes. The only place I know where to find it is oscilloscope part mules.
Essentially it was transmission line with a ridiculously low velocity factor. It is great for building instant digital delay lines up to the low 10s of nanoseconds range in a small space. On Mon, 17 Dec 2012 20:04:15 -0500, Bob Camp <li...@rtty.us> wrote: >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 <hmur...@megapathdsl.net> wrote: > >> >> li...@rtty.us 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, t...@leapsecond.com 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. _______________________________________________ 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.