[time-nuts] 50 vs 75 ohm cables
Peter Vince
pvince at theiet.org
Thu May 10 12:39:27 UTC 2007
I came across some telecom equipment the other day which had
reference outputs marked as 75 ohms. I work in television, not
telecoms, and we use 75 ohm connections for video, but with most RF
stuff being (I believe) 50 ohms, and certainly all the HP and other
counters seem to have 50 ohm inputs, I rather assumed telecoms used
50 ohms - obviously not! Can anyone tell me how and why the 50/75
ohm distinction came about? Was it perhaps a VHS/Betamax type issue
with different manufacturers going their own ways, and then with so
much equipment out in the field, neither side was willing to change?
Thanks,
Peter (London)
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