On Sun, 28 Aug 2005 09:38:52 -0700, dansawyeror
wrote:

Wes,

As a starter, look at this site:

http://www.cbtricks.com/~ab7if/coax/coax.htm

When a transmission line is terminated in it's characteristic impedance there is
no voltage or current reflection from the line. The electromagnetic fields
continue to flow into the termination as if the line were infinitely long. When
a mismatch of impedance occurs, reflected waves will be produced and they will
interact with the incident waves. The total voltage and current on the line are
no longer the result of a single traveling wave from the source to the load.
Instead, it is the algebraic sum of two waves traveling in opposite directions.
This interaction results in what is known as standing waves. The waves remain in
fixed positions along the line while they vary in amplitude and polarity. A wave
of any shape can be transmitted along the line without any change of waveshape
or magnitude. Looking at the gif below, we see a line driven with a sine wave
generator, terminated with a short circuit to maximize the reflection.

I am certainly not the sharpest guy in this forum, however, I have
been a ham for almost 47 years and I've been working with antennas
from the beginning. I retired after 33+ years in the aerospace
business where a good deal of my work involved rf design,
measurements, failure analysis and the writing of specifications for
rf/microwave devices and assemblies. I regret having to even bring
this up, but it seems that you're willing accept something written on
a CB radio site as fact while ignoring anything you hear in this forum
from professionals in the field. Why is that?


My first claim is a tuner at the source does not materially improve what is
happening in the coax.

Please show me the place where I claimed anything different.

That is a tuner does not recreate the condition above
where the coax is functioning as a properly
matched and terminated transmission
line. All the tuner does is match the impedance at the coax source back to some
known, usually 50 Ohm, value.

Please show me the place where I claimed anything different.


My second claim is when the mismatch condition at the coax destination, i.e.
antenna that may result in significant radiation from the coax itself.

This I've already proved to be wrong by example. Let me try one last
time. Since antennas are reciprocal, you don't even need a
transmitter. Connect any length of coax to your receiver input.
Terminate the far end with a dummy load (50 ohm resistor). Tune around
the bands. What do you hear? Nothing, if the coax is any good and the
receiver and dummy load are well shielded. So I suppose this proves
one of your claims, a matched line doesn't radiate.

Remove the dummy load and replace it with a short circuit. What do
you hear now on this totally mismatched line that by your reckoning
should radiate like crazy?