Richard Clark wrote:

On Sun, 23 May 2004 02:07:13 GMT, "Henry Kolesnik"
wrote:


I know that any power not dissipated by an antenna is reflected back to the
transmitter. Then the transmitter "reflects" this reflection back to
antenna, ad nauseum until its all gone. I also know that a short or an open
is required to reflect power and I'm searching for which it is, an open or a
short. I'm inclined to think it's a virtual open but I'm at a loss to
understand that and I wonder if someone has a good explanation or analogy
and some math wouldn't hurt.
tnx
Hank WD5JFR



Hi Hank,

At last count there are 130 responses to this post, this is #131, and
the question still hasn't been answered.

When energy or power is transmitted in any medium where the wavelength
and the length of the transmission medium are significant percentages of
one another some energy/power is reflected at any discontinuity in the
transmission medium. The reflected energy/power may be re-reflected if a
discontinuity exists in the backward path.

The simplest example that we can all understand is the common case of
the echo!! H E L L O ! .... HELLO ! .... hello ! .... etc. The
energy/power is re-reflected many times until we can't hear it. But is
is still re-reflecting at sub-audible levels until 100% dissipation
occurs. As long as the discontinuities exist the echoes exist!

DD, W1MCE


What you describe as reflection and re-reflection occurs between the
mismatched antenna and the tuner that has been adjusted to minimize
power returned to the transmitter. The sole function of the tuner is
to keep this power from being dissipated by the transmitter (common
experience of arcing, denoting a voltage reflection, or thermal
runaway, denoting a current reflection). The "virtual" reflection
(offered by the tuner) is generally know as the complex conjugate of
the remote load, seen at the near end of the line through which it is
returning. This means that the line transforms the phase and
amplitude of the reflection, and the tuner's job is to invert that
relationship to counteract it, and return it to the antenna.

There are both wave descriptions of this process, and lumped circuit
equivalents. Both work, and both describe the same process from
different points of view. One does not negate the other's validity
(unless, of course, you attempt to mix the points of view and demand
consistency in terms - a frequent rhetorical trap here).

There will no doubt be a flurry of denials to this simple example with
contortions of logic to match. As for the math, you will find it by
the reams, once you've been overwhelmed with the arcana of hyperbolic
descriptions of a novel physics that have to proceed its proof.

Keep your eye on how your literal points in your question go abandoned
with these arcane theories.

73's
Richard Clark, KB7QHC