[time-nuts] Why a 10MHz sinewave output?

Attila Kinali attila at kinali.ch
Tue Feb 7 21:03:27 UTC 2012

On Tue, 7 Feb 2012 21:59:18 +0100
Attila Kinali <attila at kinali.ch> wrote:

> > Related question:   Assuming I'm using 10MHz sine wave.   What's the
> > best physical cable to use?  Is there any good reason to use 50 ohm
> > cable?   What about 75 ohm?   I looked at a schematic of my counter
> > and it looks like the 10MHz signal hits some high impedance chip
> > inside.    RG6 seems like the way to go.   It's double shieled and
> > lots of cable TV parts could be used.
> There is no particular advantage in one or the other, at least not
> for most applications. It's tradition that measurement and (most) RF
> gear uses 50R, while TV and radio uses 75R. (there was once a reason
> for this, but i don't know it).

Addendum: Your counter input is mostlikely 50R. Even if it just enters
a chip, as the chip itself should be matched to 50R. The input impedance
should be noted in the manual of the counter.

			Attila Kinali
Why does it take years to find the answers to
the questions one should have asked long ago?

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