Telamon wrote (in part):

You need more bandwidth for digital signals because of the faster rise
and fall times. For data to be valid you need a large eye opening in
amplitude and time for margin.

There are two things of significance:
1. The amplitude of the discontinuity.
2. The length of time of the discontinuity.

#1 determines the amplitude of the reflection.
#2 determined the frequency it becomes significant.
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I started this thread because starting now and increasingly
in the near future there will be "lots" of analog "75 Ohm" video
patch bays, and patch hairpins, and patch cables dumped as the
older ones degrade digital signals. At one local station they found
out they could go through one set normally normaled analog patch.
Inserting eithr a hairpin, short patch used to connect adjacent non
normally connected patches, or any patch cable "killed" the digital
data stream.

I was given a~25 year old 48 bay patch with hairpins and cables.
And while my current antenna system is "50 ohms", this bay passes
signals in the .1`~30MHz range with "no" attenuation. By "no", I can
dirrectly feed the attenuated output from my ancient HP test generator,
adjust it for a just audible signal, then run it through the patchbay,
and it
is still there.

Beats the heck out of my homebuilt BNC bay, and I can now seperate
my receivers from my transceivers.

I did a quick search and found Prompeter 75 ohm patch bays on Ebay
for less then $20. For anyone with a mix of receivers, converters,
filters,
and antennas, this could be a very cost effective routing solution.

And for those who think that their SW receiver antenna input,
rated at 50 ohms, is really 50 Ohms, all I can say is "not very
likely".

As to the mismatch of using a 75 Ohm patch in a 50 ohm system,
I can run 146MHz through a patch set, terminate it in a Narda 50
Ohm load, and I can not measure any increase in VSWR. This is at
low power and one of my main reasons for wanting to not use my BNC
bay is to avoid, or at least decrease the chance of feeding the output
of my IC28A, or HTX100 directly into a receiver. While I haven't
managed it, I know one friend who did.

Terry