Wait a minute here... Seems to me that Reg is talking about two
opposing steps separated by a very short distance, and Richard is
talking about a single step from one impedance to another. Clearly,
Richard's case results in uncancelled echos related to the ratio of
the impedances at the step. In fact, Reg's example results in
significant uncancelled echos if the steps are separated by enough
distance: worst at odd multiples of pi/2 electrical degrees. When the
connector is only perhaps a few electrical degrees long, the steps
nearly cancel. How long is 1", in electrical degrees? Well, at
1000MHz and a v.f. of perhaps 0.7, longer than one might have
anticipated: almost 45 degrees long. So in fact at 1000MHz, a 1"
section of 51.5 ohm connector might introduce a bit more than 1.03:1
SWR. But didn't we start out talking about a much lower frequency,
and a much larger impedance difference? Another example I ran was 4
electrical degrees of connector...perhaps a bit less than an inch at
150MHz...where it's 75 ohms in a 50 ohm system. The swr for that came
out about 1.06:1.

The TV broadcast engineer should worry about things like that. The
typical ham doesn't have equipment calibrated accurately enough that
s/he should be worried about it, and it's unlikely to make any
substantive difference anyway in typical ham work.

Cheers,
Tom

"Richard Fry" wrote in message ...
"Reg Edwards" wrote
Richard, I have no reason to doubt anything you say.
I have no reason to doubt what I have said.
But why imply there's serious disagreement when there is none?
_______________________

Clips from our previous posts (below) -

I don't know what constitutes a "serious disagreement" to you, Reg, but I
think most readers would say that we have opposite conclusions about this
topic.

If you have no reason to doubt what I wrote about this, how can you continue
to support what you wrote? Our statements are mutually exclusive.

YOU: "Provided the mechanical connection is sound, you can use any coaxial
connectors you like, regardless of nominal impedance, at frequencies less
than about 300 MHz without any observed ill effects. A connector less than
1" long of impedance 51.5 ohms in a 50 ohm system will NOT produce an SWR of
1.03:1 or anything anywhere near to it at frequencies less than 1000 MHz."

ME: "This PRACTICAL experience illustrates that an impedance change even in
a 54-60MHz TV channel occurring within a physical space of less than one
inch can produce important and commercially supportable system benefits,
despite your statements quoted above."

- RF