Richard Clark wrote in
:

On Mon, 10 Dec 2007 21:04:06 GMT, Owen Duffy wrote:

I can't quickly think of a sampling technique that truly takes a
point sample.

Slotted line.

73's
Richard Clark, KB7QHC


Thanks Richard and Jim,

I mean't literally a point sample, and I doubt that we can manufacture a
probe for either voltage or current that has zero dimensions (ie is
influenced ONLY by conditions at a point of no physical size.).

I go on to say (if you read on) in different words that notwithstanding
that, practical probes can be made that give acceptable accuracy.

They unsaid key thing is that these probes do not depend on averaging
over a length of line (as Roger suggested), that is actually a defect
that limits their usable upper frequency.

Owen