[time-nuts] Practical considerations making a lab standard with an LTE lite
hmurray at megapathdsl.net
Tue Nov 25 00:23:57 EST 2014
Said Jackson said:
> Correct, and thats why its all a bad trade off if you have to use 50 Ohms
> termination. Either more heat or more PN, and more circuitry.
> So driving 50 Ohms inputs is not optimal here, 1M inputs are much better for
> this purpose.
That only works if you have a (very) short connection to the next stage.
Things get interesting if you have, say, 10 feet of unterminated coax.
10 MHz is 100 ns, or 50 ns between transitions. Coax is ballpark of 5/8 c so
that's 16 ns one way or 32 ns round drip. That's 60% of the heat as well as
lots of nasty reflections.
(Somebody please check my numbers.)
These are my opinions. I hate spam.
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