howard parkin wrote:
Getting high speed analog video across the DVI-I analogue
pins is a big concern for me. However, the DVI-I connectors
are staying.
I know a company that uses a DVI-I to 5 x BNC cable. The monitor
that they drive is 50ohm. This is even more surprising as I'm sure
this is wierd ;D
care to share a link to that monitor ?
the DVI-I connector was designed with 75 ohm signals in mind.
But this company seem to get away with it.
Maybe the impedance mismatch over a small distance is not
a big issue. Maybe there's somebody out there who is proficient
enough with Spice and lossy transmission line modeling
to figure it out. I tried once, but got lost in the Math.
ok.
from experience, the impedance is important over longer distances, more
so in digital transmissions than in analog.
for instance, I successfully transmitted video between 2 75ohm "things"
(monitor, vcr, whatever) using a 5m 50ohm cable we had lying around (we
didn't have enough 75 ohm cables, and a purchase order for new one was
sent out the same day)
however, for digital transmissions, mismatching the impedance litterally
destroys the eye pattern, and the decoder on the other end can't figure
the signal out.
Howard.
Raphael
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