Owen Duffy wrote:
No Cecil, the thread subject and the quote of your text in the first
message of the post was the main point of discussion:

Yes, the thread subject was the main point. Z0's other than 50
ohms do not force the V/I ratio to 50 ohms (for matched lines)
and 2% of a 10 MHz WL of RG-213 is of a *sufficient* length to
force the V/I ratio to 50 ohms.

The transmission line length must only be long enough such that
the V/I ratio is forced to the Z0 value. According to some pretty
smart guys I asked, that's about 2% of a wavelength.

I've already apologized for my memory being faulty on that one.
If what you want are additional apologies, you've got it. I
hereby triple dog apologize for my faulty memory. The above
statement was incomplete and was therefore wrong. What more
do you want me to say about it? It was wrong, so of course,
it "is not born out in practice".

It seems that the statement you have quoted is not born out in
practice, though I note that you "seriously doubt that is true".

What I seriously doubted being true is that a 50 ohm Bird wattmeter
has a 0.2 reflection coefficient when placed in a 75 ohm feedline.
I just don't think that 40mm (1.5") is enough length to establish a
50 ohm environment inside the Bird. But I might be wrong on that one.
I know my Autek WM-1 doesn't cause appreciable reflections when
placed in a 75 ohm feedline.

I think, from the beginning, you have confused what Reg said with
what I said. I am basically on your side in the argument.

***Additional Context***
The question of a year ago was not what is the minimum length
required to force V/I to Z0 (although that can be had from Kevin's
posting quoted from s.p.e.) I was arguing with Reg over whether
the lengths of coax into and out of *my* SWR meter forces V/I to
be 50 ohms. I use two foot lengths of RG-400. (That's ~2% of a
wavelength at 10 MHz.) Two feet is a *sufficient* length to cause
V/I to equal Z0 (in a matched line). Two feet is not the *absolute
minimum* length but is instead a *sufficient* length and the length
I use in my shack.
--
73, Cecil http://www.qsl.net/w5dxp