Like this?
http://www.ebay.com/itm/Tektronix-Delay-Line-for-475-Oscilloscope-New-/290824098279?pt=LH_DefaultDomain_0&hash=item43b67791e7
Em 17/12/2012 23:39, David escreveu:
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 <[email protected]> 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 <[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.
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