I have seen the small diameter, about like RG-174, delay cable used for patching PC boards after the fact. That is how I know it exists. :)
I just have not found a source for it. On Mon, 17 Dec 2012 20:47:34 -0500, Bob Camp <li...@rtty.us> wrote: >Hi > >At some point the whole get it onto the board / get it off the board thing >becomes the main issue. Then it's easier to just make the delay line part of >the PC layout. > >Bob > >On Dec 17, 2012, at 8:39 PM, David <davidwh...@gmail.com> wrote: > >> 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.
