On Sun, 4 Nov 2007 22:10:19 -0700, "Sal M. Onella"
wrote:


"Owen Duffy" wrote in message
...
"Sal M. Onella" wrote in
:

as heat somewhere in the system. If too much is reflected back from
the antenna and dissipated within in your transmitter, the transmitter
overheats ($$$) or it reduces power to protect itself and nobody hears
you.

Here we go again!

Owen

What did I say wrong?

You offered only half the evidence, as in the following instance:

On Sun, 4 Nov 2007 22:30:30 -0700, "Sal M. Onella"
wrote:


"Cecil Moore" wrote in message
news
Roy Lewallen wrote:
Yes, this misconception will never die. Is it really worth the trouble
continually trying to contradict it?

Not if all you do is trade one old-wives tale
for another.

It's hardly an old wives' tale.

I mistakenly put a 2m antenna on my dual band HT and tried to use it for a
short QSO on a nearby 440 repeater. The other ham said I was barely making
the repeater, while my poor HT got so hot that I could barely hold it after
a minute's use.

The antenna was wrong and the heat was real -- whatever the theory behind
it.

In the explanations that hammered you for your naivete, there was no
support of what was obvious to you, and perfectly acceptable as a true
portion of a complete description. You testified to the experience of
observing more heat where odds would have had you as likely testifying
to the experience of observing less heat. We get none of those "less
heat" reports because they naturally go unobserved. This is simply
the common response to a psychomotor lesson instructed from Mom who I
am sure warned you to "never stick your hand in the oven" but probably
never uttered "never stick your hand in the ice-box." The first bears
warning for its obvious consequences, the second hardly demands
mentioning where its consequence is far less dramatic.

So we have these dramas over heat and the stage is filled with tenors
crying their lungs out about the evils of misunderstandings (the last
act of "Romeo and Juliet" comes to mind).

We should also first establish that your HT also exhibits waste heat.
As no common transmitter of notable power is 100% efficient, it is
raising its heat content in relation to its surroundings. If your
hand temperature is cooler than that case surface, you note heating;
contrariwise, if your hand temperature is warmer than that surface,
you note cooling. As almost every item within reach of you is at room
temperature and you rarely note it as cooler, it is hardly worth
mentioning.

Your's was a sin of omission and what "you said wrong" was more in
that neglect of mentioning all the cooling experiences in your life
when your HT was mismatched. Of all the web pages, treatises, papers,
tomes, chapters and verses dedicated to eradicating the myth of
reflected power, all of them are equally sinful in their omissions.
You are not alone there in Reflected Power Hell.

Let's begin first with "reflected power." It is in fact reflected
energy that is noteworthy here, power is merely the manifestation of
energy at a load. With this discussion of the HT and an antenna,
there are two loads (and this raises the tenor's volume of agony
another octave - I will leave that Operetta for other discussion).

The HT as a load is already exhibiting waste heat. Everyone's
experience of operating one for several minutes will testify to that
(yes, more anecdotal evidence) even when it is pushing energy into a
matched load. Let's take the experience of your mismatch and put that
antenna on a variable transmission line (one of those bench top tools,
aka the "Sliding Load," few here have had experience with) and run the
line through 360° of variation as noted at the source (your HT). This
study will fill in all those omissions from those publications so
cleverly painted up and distributed across the web as sage advice.

When that returned energy meets the source energy and combines at the
source, there are 360° of variation possible outcomes. This
combination can be in series aiding, in series opposition, or in all
points in between. This will be a function of the length of the
variable line. You add two aiding energies to the same load and it
will raise its temperature against waste heat. You add two opposing
energies to the same load and it will subdue its temperature against
waste heat. These are the extreme outcomes that fall 180° apart based
on the length of that variable transmission line. One outcome burns
your hand, as you've already noted, the other does not (and you
neglected to inform us of all those occasions you naughty boy!). All
the combinations in between were by relation, inconsequential, and
passed unnoticed (even more sins of omission).

Hence, the problem of anecdotal evidence is that it does not report
fully. However, applying the label "anecdotal" does not automatically
invalidate the observer's credible but isolated reporting; it merely
demands a fuller examination. Unfortunately, you were denied this
full examination in the criticism of your true observation. You
observed one data point and perhaps were guilty of expanding it to
describe a general condition = reflected power always heats a source.
In fact, reflected energy can heat or cool a source in relation to its
existing waste heat. The degree of heating or cooling is found in the
magnitude of the mismatch, and the number of degrees that separate the
load and the source.

As for all the side comments about how "reflections" do not contain
(fill in the blank) ______; and that these issues are instead answered
by Impedance relationships instead - Baloney cut thick. Reflections
AND Impedance relationships occupy opposite sides of the same coin and
are equally applicable. This concept of mutuality is so ingrained in
the catechism of RF as to taint anyone who denies one explanation for
the sake of the other as evidence of some special circumstance. In
this regard, you were sinned against in kind. ;-)

73's
Richard Clark, KB7QHC