20 Oct
2004
20 Oct
'04
8:44 a.m.
From: "Paul Koning" <pkoning(a)equallogic.com>
Ethan> Sorry... never even _seen_ those. You
could probably make a
Ethan> set from a prototyping card and some ribbon cable, though.
That may not work... you want controlled impedance cable. I looked
for the spec, but didn't see it; it may be the same as Unibus cable,
which is documented in the Unibus handbook.
Conventional ribbon cable is not controlled impedance, though there
exists higher end cable that is.
It is pretty easy to find ribbon that is spec'd for impedance. It would say
it is more a matter of avoiding the low-end ribbon, these days.
The older Negibus/Posibus cables are spec'd for 93 ohm coax. I suspect
you'd do OK with 100 ohm ribbon.
I think a tougher issue with ribbon is how to keep the cables from sitting
on top of each other and having a mess of crosstalk. The older coax doesn't
have that problem :-). I am also building a few Negibus/Posibus cables out
of CAT5e, in an attempt to mitigate that problem.
Vince