question about wire antenna and tuner
 

Ian White GM3SEK wrote:
If you measured the impedance of that incorrect antenna, and then
replaced the antenna with a dummy load of the same impedance (a resistor
of the correct value, in series with an inductor/capacitor of the
correct value) then your transmitter will not know the difference.

It is true that transmitters are dumb as a stump. However,
a human being should be smart enough to realize that the
virtual impedance, which is only a voltage to current ratio
has been replaced by an impedor with a resistor, inductor,
and/or capacitor.

The impedor *causes* the load conditions. That virtual voltage
to current ratio is a *result* and not the cause of anything.
To get down to the actual cause of the conditions, the human
being needs to know whether the load impedance is virtual or
not.

Why do you imply that a virtual impedance can *cause* the
conditions seen by a source but deny that a virtual impedance
can *cause* 100% re-reflection? Seems a contradiction.
In fact, virtual impedances cannot cause anything. The
voltage to current ratio associated with a virtual impedance
is a *result* of something physical. Choosing to ignore that
physical "something else" cause has gotten lots of folks into
logical trouble.

In the huge majority of applications, both amateur and professional, it
IS possible to separate those two topics cleanly and completely. It
seems perverse to tangle them together unnecessarily.

It seems perverse to say the antenna system can be replaced
by a resistor and inductor or capacitor and nothing changes.
How about the radiation pattern? Does that change?

It should be
absolutely no surprise that, when summed to an infinite number of terms,
this series produces exactly the same results as the steady-state model
- exactly the same pattern of standing waves, and exactly the same load
impedance presented to the transmitter.

How about the total energy in the steady-state system? The
number of joules pumped into the system during the transient
state is *exactly* the amount required to support the forward
and reflected power readings.

The important conclusion from this more detailed time-dependent analysis
is that re-reflections at the transmitter have NO effect on the final
steady-state pattern of standing waves.

This is based on a rather glaring rule-of-thumb assumption,
that any standing wave energy dissipated in the source was
never sourced to begin with. Born of necessity, that is a
rather rash assumption. Thus some people sweep the reflected
energy dissipated in the source under the rug and forget
about it, hoping that nobody ever lifts the rug and points
out the conservation of energy principle.

I await the inevitable photon explanation.

None needed. If anyone wishes to introduce additional complications
where none are necessary, then of course they're at liberty to do so.
But when invited to join in, everyone else is at liberty to decline.

Optical physicists did not have the
luxury of dealing with voltages. As a result of dealing with
power densities, they learned a lot more than RF engineers
know to this very day. Optical physicists have never asserted
that reflected waves are devoid of ExB joules/sec or that
EM waves are capable of "sloshing around".
--
73, Cecil http://www.w5dxp.com

question about wire antenna and tuner
 

Roy Lewallen wrote:
People who believe
that "reflected power" ends up heating up the transmitter should take a
careful look at this, and see if they can explain it.

I have taken a careful look and have explained it using the
principles of destructive vs constructive interference between
EM waves adopted from the field of optical physics. Power density
in any EM wave is proportional to ExB and that includes reflected
waves in a transmission line. Your attempt to ignore the technical
facts about the necessity for energy content in reflected waves is
pretty obvious.

But they can never come up with a coherent reason for
the results shown in the essay table, or equations which will predict
just how much "reflected power" a transmitter will absorb and when. And
the reason is just as Ian said.

It is untrue that those coherent reasons do not exist. I have
pointed out those "reasons and results from the field of optical
physics and you have simply chosen to sweep them under a rug.

Unfortunately, some people, when presented clear evidence that the
concept is wrong, cling desperately to it nonetheless.

Unfortunately, some people, when presented with clear evidence
that everything is explained perfectly by interference phenomena
and the conservation of energy principle, cling desperately to
"sloshing" EM waves and reflected EM waves devoid of any energy
content - something to do with motes and beams.
--
73, Cecil http://www.w5dxp.com

question about wire antenna and tuner
 

Roy Lewallen wrote:
Once a black cat walked across the street in front of me. I had a
wonderful day! The wonderful day was real, whatever the theory behind
it. My basis for crediting the cat is just as valid as yours for
crediting "reflected energy" for the heating. And based on similar logic.

One can mentally install a one-wavelength piece of lossless
transmission line between the source and load which will
allow one to analyze the interference patterns. Constructive
interference toward the source certainly can cause heating
of the source in perfect accordance with the conservation
of energy principle.
--
73, Cecil http://www.w5dxp.com

question about wire antenna and tuner
 

Highland Ham wrote:
Roy Lewallen wrote:
But I did write up a lengthy essay several years ago, in response to
the same insistent rantings about reflecting waves of average power
that's still going on in this newsgroup, and it has some numerical
examples with a very simple circuit which illustrate the problems with
what you said. You can get it at
http://eznec.com/misc/Food_for_thought.pdf.
===========================
Roy ,Tnx vy much for that ,much appreciated. ( it now sits in my
'Antenna' file)

Unfortunately, all it proves is that reflected power
doesn't always cause heating of the source. It does
not prove that reflected power never causes heating
of the source but that seems to be what w7el would
have us believe that he has proven.

If constructive interference between reflected waves
is in the direction of the load, the source will run
cool and the load will run hot. An antenna tuner can
accomplish that configuration.

If constructive interference energy flows unimpeded
backwards into the source without being re-reflected,
the source will run hot and the load will run cool.

This is no-brainer conservation of energy stuff.
Simply calculate the total number of joules contained
in the closed system and observe where those joules go.
Hint: the total number of joules contained in the
system are *exactly* the number of joules needed to
support the joules/sec in the forward and reflected
power readings.
--
73, Cecil http://www.w5dxp.com

question about wire antenna and tuner
 

Roy Lewallen wrote:
Once a black cat walked across the street in front of me. I had a
wonderful day! The wonderful day was real, whatever the theory behind
it. My basis for crediting the cat is just as valid as yours for
crediting "reflected energy" for the heating. And based on similar logic.

But, once again, you left out some important details.
The black cat belonged to your neighbor who gave you
$100 for not running over it and that's why you had
a wonderful day. :-)
--
73, Cecil http://www.w5dxp.com

question about wire antenna and tuner
 

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
...
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

question about wire antenna and tuner
 

Cecil Moore wrote:
Ian White GM3SEK wrote:
If you measured the impedance of that incorrect antenna, and then
replaced the antenna with a dummy load of the same impedance (a
resistor of the correct value, in series with an inductor/capacitor
of the correct value) then your transmitter will not know the difference.

It is true that transmitters are dumb as a stump. However,
a human being should be smart enough to realize that the
virtual impedance, which is only a voltage to current ratio
has been replaced by an impedor with a resistor, inductor,
and/or capacitor.

The impedor *causes* the load conditions. That virtual voltage
to current ratio is a *result* and not the cause of anything.

At the terminals of the load, both the voltage and current are
physically real and physically measurable, as also is the phase angle
between them. Their ratio is the (complex) load impedance as seen by the
transmitter.

Any device that creates those same electrical conditions possesses the
same impedance; by definition.

The transmitter affects the magnitude of the voltage and current in the
load, but it categorically does NOT affect their ratio, or the phase
angle. In other words, the transmitter has no effect on the value of the
impedance that is connected to it as a load, That value is created
exclusively by the load.


To get down to the actual cause of the conditions, the human
being needs to know whether the load impedance is virtual or
not.


I can see your underlying point, about the difference between a lumped
impedance physically present at the transmitter output terminals, and an
impedance created by 'action at a distance' through a transmission line.
But if both kinds of load create the SAME steady-state voltage:current
ratio and phase angle at the transmitter output terminals, then by
definition they both have the SAME impedance, and the transmitter will
respond in EXACTLY the same way. There is no steady-state measurement
you can possibly make on the transmitter than can tell the difference
between those two different kinds of load.

That principle is absolutely fundamental. It underlies all steady-state
impedance measurements using bridges, network analysers etc. Regardless
of the nature of the DUT (device under test), you connect it to the
meter, measure what you find, and that IS "the impedance of the DUT".

The differences only appear if you change frequency, or if you make a
time-dependent measurement, but there is never a difference in the
steady state.


Why do you imply that a virtual impedance can *cause* the
conditions seen by a source but deny that a virtual impedance
can *cause* 100% re-reflection? Seems a contradiction.
In fact, virtual impedances cannot cause anything. The
voltage to current ratio associated with a virtual impedance
is a *result* of something physical. Choosing to ignore that
physical "something else" cause has gotten lots of folks into
logical trouble.

I invite you to consider another possibility: that the people who have
chosen to stick with the established textbook analyses are not ignoring
anything, and they are in no kind of logical trouble because those
analyses are both logical and consistent; and that the only person in
logical trouble is actually yourself, because you are making
distinctions between different varieties of impedance that do not exist.


In the huge majority of applications, both amateur and professional,
it IS possible to separate those two topics cleanly and completely. It
seems perverse to tangle them together unnecessarily.

It seems perverse to say the antenna system can be replaced
by a resistor and inductor or capacitor and nothing changes.
How about the radiation pattern? Does that change?


Nothing changes in the part of the system I was talking about, namely AT
the transmitter/load interface. (Lord, gimme strength...)

It should be absolutely no surprise that, when summed to an infinite
number of terms, this series produces exactly the same results as the
steady-state model - exactly the same pattern of standing waves, and
exactly the same load impedance presented to the transmitter.

How about the total energy in the steady-state system? The
number of joules pumped into the system during the transient
state is *exactly* the amount required to support the forward
and reflected power readings.

If you say so; but nobody else feels the need to calculate those
quantities.

The important conclusion from this more detailed time-dependent
analysis is that re-reflections at the transmitter have NO effect on
the final steady-state pattern of standing waves.

This is based on a rather glaring rule-of-thumb assumption,
that any standing wave energy dissipated in the source was
never sourced to begin with. Born of necessity, that is a
rather rash assumption. Thus some people sweep the reflected
energy dissipated in the source under the rug and forget
about it, hoping that nobody ever lifts the rug and points
out the conservation of energy principle.

All valid solutions to the problem of AC/RF generators, transmission
lines and loads will most assuredly comply with the conservation of
energy! But countless textbooks show that it isn't necessary to invoke
that principle in order to make a valid analysis.


I await the inevitable photon explanation.

None needed. If anyone wishes to introduce additional complications
where none are necessary, then of course they're at liberty to do so.
But when invited to join in, everyone else is at liberty to decline.

Optical physicists did not have the
luxury of dealing with voltages. As a result of dealing with
power densities, they learned a lot more than RF engineers
know to this very day. Optical physicists have never asserted
that reflected waves are devoid of ExB joules/sec or that
EM waves are capable of "sloshing around".

But WE DO enjoy the luxury of having complete information on voltages,
currents and phase angles, at any instant and at every point along a
transmission line. That allows us to obtain complete solutions without
dragging in unnecessary concepts from other disciplines.



--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

question about wire antenna and tuner
 

Ian White GM3SEK wrote:
Any device that creates those same electrical conditions possesses the
same impedance; by definition.

Sorry Ian, that's just not true. There are three separate
definitions for impedance in "The IEEE Dictionary". If all
those were the same impedance, they wouldn't need three
definitions. A resistor has a resistance. The Z0 of a
transmission line is a resistance. They are NOT the same
impedance, by definition. The IEEE Dictionary says:
"Definition (C) is a second use of "impedance" and is
independent of definitions (A) and (B)." (C) is the
definition of impedance associated with a resistor,
inductor, or capacitor. (B) is the definition of impedance
associated with a voltage to current ratio. The IEEE
Dictionary goes out of its way to explain that there is
a difference.


The transmitter affects the magnitude of the voltage and current in the
load, but it categorically does NOT affect their ratio, or the phase
angle.

Strawman

But if both kinds of load create the SAME steady-state voltage:current
ratio and phase angle at the transmitter output terminals, then by
definition they both have the SAME impedance, and the transmitter will
respond in EXACTLY the same way.

Although they may have the same value of impedance components,
they are NOT the same impedance, by IEEE definition. See above.

That principle is absolutely fundamental.

Too bad that your underlying absolutely fundamental
principle is wrong according to the IEEE Dictionary.

... because you are making
distinctions between different varieties of impedance that do not exist.

I'm just following the IEEE lead. You, OTOH, are in
logical trouble for disagreeing with the IEEE.

All valid solutions to the problem of AC/RF generators, transmission
lines and loads will most assuredly comply with the conservation of
energy! But countless textbooks show that it isn't necessary to invoke
that principle in order to make a valid analysis.

Please show me a textbook that gives you permission to
ignore the conservation of energy principle.

But WE DO enjoy the luxury of having complete information on voltages,
currents and phase angles, at any instant and at every point along a
transmission line. That allows us to obtain complete solutions without
dragging in unnecessary concepts from other disciplines.

But you guys even ignore the laws of physics for electrical
engineering, e.g. Vfor*Ifor=Pfor and Vref*Iref=Pref
--
73, Cecil http://www.w5dxp.com

question about wire antenna and tuner
 

Ian White GM3SEK wrote in
:

Ian, an excellent and quite comprehensive treatment.

Sal,

Some folk will try to distract from an adequately accurate approximation
(being the steady state solution) by wanting to descend to a time domain
solution which as you note converges to the steady state solution in
time, but is much more complex to solve.

The relevance of steady state solutions is demonstrated by the
traditional methods of designing transmission line transformers (eg
quarter wave match), stub matching schemes, the application of the Smith
chart etc. These things are only valid on applications where a steady
state solution is valid, and the widespread use of them attests to the
widespread existence of systems that are quite adequately analysed by
steady state methods.

Most ham applications are ones where the highest modulating frequency is
very small wrt the carrier frequency, and are emminently suited to steady
state analysis.

Similarly, consider that when steady state analysis is not appropriate,
then many of the devices mentioned above may be inappropriate as they
will cause distortion of the signal.

Owen

question about wire antenna and tuner
 

"Richard Clark" wrote in message
...
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
...
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

So, when you were on staff at USN ET "A" School, where we both taught, did
you know better than the "reflected power" legend/old-wives-tale/heresy?
Hell, that's where I first picked it up !!!!!!!!!!!!!!!

John

question about wire antenna and tuner
 

"Cecil Moore" wrote in message
...
Sal M. Onella wrote:
What did I say wrong?

You implied that reflected energy is always dissipated
in the transmitter.

Yeah -- well, I was trying to keep it simple, as I said to start the second
paragraph.

Tell me something, please: with a mismatched load, isn't overheating of the
transmitter sometimes a risk? (Assume no tuner, 50 feet of coax and an
assortment of attempted HF transmit freqs.)

How much of the reflected energy is dissipated in the
source depends upon the interference pattern at the
source. As w7el points out, dissipation in a voltage
source can be reduced to zero by the astute choice of
a special best case of complete constructive
interference in the direction of the load.

.... and I think I see an example of the "astute choice" illustrated by the
"ladder-line length selector for our all-band dipole" on your website. I
get that and I like it but it would never have occurred to me -- probably
because of lack of wave theory on my part. Am I right?

Thanks.

question about wire antenna and tuner
 

Think, this is the same thing that one "Kurt N.Sturba" says in
his columns, about swr: It Isn't LOST power
(Heating the final or , dissipated in the final),
but is redirected to the load (again). Tho might be sticking
my foot in mouth again, but the ONLY effect of SWR, would
be on the Transmission Line (because of the loss of THAT line)
First, because of the loss, to the load.
Second , because of the Reflected LOSS (again!)towards the Source.
And then The loss, as it is again redirected towards the
load! In short, SWR, doesn't effect the power-- the FEEDLINE does
and the higher the swr- the higher the loss the feedline presents to
the load! See World Radio magazine for his tomes! In short ,
MAXIMUM power transfer occurs when the impedence of the source= the
impedence of the load. But that doesn't mean that the power is lost
at the SOURCE as (heat, loss, ect). ANY loss must be in the (devices)
between the source , and the load! Jim NN7K

Roy Lewallen wrote:
Sal M. Onella wrote:

What did I say wrong?


As always, Ian has done a much better job than I could have, so there's
not much point in trying to repeat what he said.

But I did write up a lengthy essay several years ago, in response to the
same insistent rantings about reflecting waves of average power that's
still going on in this newsgroup, and it has some numerical examples
with a very simple circuit which illustrate the problems with what you
said. You can get it at http://eznec.com/misc/Food_for_thought.pdf. A
little past half way down is "Food for thought: Forward and reverse
power". If you're not interested in the math, scroll down a few
paragraphs from there to the table in Courier font. It and the text
below explain how it shows where the source dissipation is higher,
lower, and about the same when the load is matched, for three different
loads all having the same "reverse power". Another entry in the table is
an example where the "reverse power" equals the forward power (an
infinite SWR) yet the source dissipation is zero. People who believe
that "reflected power" ends up heating up the transmitter should take a
careful look at this, and see if they can explain it.

The established transmission line theory that's been well established
for over a century and that Ian, I, and countless others use daily for
solving real problems will, as shown in the example, tell us exactly how
much power is where and why. The "power is absorbed in the load" folks
can point to transmitters that get warm (sometimes) when working into
(some) mismatches. But they can never come up with a coherent reason for
the results shown in the essay table, or equations which will predict
just how much "reflected power" a transmitter will absorb and when. And
the reason is just as Ian said.

Unfortunately, some people, when presented clear evidence that the
concept is wrong, cling desperately to it nonetheless. For those,
explanations and evidence are a waste of time. But hopefully there are a
few readers out there who will see the problems in resolving their
theory with the evidence and redirect their thinking.

Roy Lewallen, W7EL

question about wire antenna and tuner
 

"Roy Lewallen" wrote in message
...
Sal M. Onella wrote:

What did I say wrong?


snip

Unfortunately, some people, when presented clear evidence that the
concept is wrong, cling desperately to it nonetheless. For those,
explanations and evidence are a waste of time. But hopefully there are a
few readers out there who will see the problems in resolving their
theory with the evidence and redirect their thinking.

Roy Lewallen, W7EL

Roy,

I don't cling to anything, desperately or otherwise. I keep an open
mind. I've learned a lot but I haven't learned everything.

Give me credit for having been the victim of conventional wisdom or
[insert your favorite disparaging term for misinformation]. It's that
simple.

Oh, and keep that "black cat" metaphor handy for any ol' time you want
to **** somebody off. It works.

"Sal"
[John Markham, KD6VKW
Amateur Extra
Commercial General
NARTE Certified EMC Engineer, retired]

question about wire antenna and tuner
 

Sal M. Onella wrote:
Tell me something, please: with a mismatched load, isn't overheating of the
transmitter sometimes a risk?

Yes, sometimes but not always. Reflected waves can
actually cool down the transmitter by reducing the
total current.

... and I think I see an example of the "astute choice" illustrated by the
"ladder-line length selector for our all-band dipole" on your website. I
get that and I like it but it would never have occurred to me -- probably
because of lack of wave theory on my part. Am I right?

Probably because of lack of Smith Chart experience?
--
73, Cecil http://www.w5dxp.com

question about wire antenna and tuner
 

"Sal M. Onella" wrote in
:

....
I don't cling to anything, desperately or otherwise. I keep an
open
mind. I've learned a lot but I haven't learned everything.


Sal / John,

I think Roy may have been referring to another 'helper' who lurks here.

Give me credit for having been the victim of conventional wisdom
or
[insert your favorite disparaging term for misinformation]. It's that
simple.

I think we were / are all vulnerable to learning from each other... it is
what amateur radio is about, the collective 'self training' that is part
of the ITU defintion of the amateur service.

Like yourself, I learned from the hobby elders, and some of it, a lot of
it was BS, and I freely admit that I am uncertain of some of what I
'know'.

We all need to test our own 'knowledge', especially the widely held stuff
that you just don't find in reputable text books. You have to ask have we
hams got an edge on the rest of the world, or is the proposition a myth.

A few years ago I worked on development of a handbook for our new six
hour hams. It was a considerable struggle to keep the 'reflected power is
dissipated in the PA and causes damage' myth out of the handbook that
would feed the hobby intake in this country.

Imagine a multiple choice question in the assessment:

Reflected power:
a) increases the power bill;
b) is a technique for operating 12V equipment in modern 24V vehicles;
c) reinforces your signal provided it is re-reflected by an ATU;
d) overheats transmitters causing serious damage;
e) is a fire hazard.


Owen

Re(2): question about wire antenna and tuner
 

"Cecil Moore" wrote in message
...
Sal M. Onella wrote:
What did I say wrong?

You implied that reflected energy is always dissipated
in the transmitter.

How much of the reflected energy is dissipated in the
source depends upon the interference pattern at the
source. As w7el points out, dissipation in a voltage
source can be reduced to zero by the astute choice of
a special best case of complete constructive
interference in the direction of the load.
--
73, Cecil http://www.w5dxp.com

You haven't commented yet pro or con, but if I may, I want to expand on
the observation I made about your variable length twin-lead arrangement
being an "astute choice" to promote complete constructive interference in
the direction of the load.

If the line length will bring this about as you have demonstrated, does
this mean that a tuner appears to adjust the effective line length (from the
perspective of the source)? The only explanation of a tuner I have seen
describes it as creating a stub whose impedance, in parallel with the
impedance of the transmission line/antenna system, is seen as 50 ohms, a
presumptive good match. I don't know enough to accept or reject this
notion, so I shall do neither at the moment. However, I think of a stub as
shunting a transmission line, whereas the tuner is electrically in series,
so maybe something's fishy about that. I withhold judgment.

More to the point, when I was taught transmission lines, they were
diagrammed with lumped constants: series resistance and inductance + shunt
capacitance. The internals of a pi tuner are just more of the same and
would seem (by intuition, alone -- I am not claiming anything) to behave as
an adjustable length line, minus the resistive component. By extension,
Does a T tuner cancel some of the reactance of the line in which it is
inserted, thereby effectively shortening the line. (The phase "conjugate
impedance" is poking out from a fold of my brain.)

Am I onto something or have I simply launched myself into the eye of
another ****storm?

"Sal"

question about wire antenna and tuner
 

Sal M. Onella wrote:
"Roy Lewallen" wrote in message
...
Sal M. Onella wrote:
What did I say wrong?


snip

Unfortunately, some people, when presented clear evidence that the
concept is wrong, cling desperately to it nonetheless. For those,
explanations and evidence are a waste of time. But hopefully there are a
few readers out there who will see the problems in resolving their
theory with the evidence and redirect their thinking.

Roy Lewallen, W7EL

Roy,

I don't cling to anything, desperately or otherwise. I keep an open
mind. I've learned a lot but I haven't learned everything.

Give me credit for having been the victim of conventional wisdom or
[insert your favorite disparaging term for misinformation]. It's that
simple.

I'm sorry, what I said was poorly worded. I wasn't directing it at you,
but was venting a bit because this misconception keeps surfacing over
and over.. I'm very glad it doesn't apply to you!

Oh, and keep that "black cat" metaphor handy for any ol' time you want
to **** somebody off. It works.

And I'm sorry if it ****ed you off. But I hope it made my point:
Observing two things doesn't mean that one causes the other.

If what I posted played any part in helping you -- or other readers --
understand transmission lines even a little better, then it was
worthwhile doing. I know Ian could have done it without ****ing anyone
off, but I'm a lot clumsier with language.

Roy Lewallen, W7EL

question about wire antenna and tuner
 

On Mon, 5 Nov 2007 17:30:26 -0800, "Sal M. Onella"
wrote:

So, when you were on staff at USN ET "A" School, where we both taught, did
you know better than the "reflected power" legend/old-wives-tale/heresy?
Hell, that's where I first picked it up !!!!!!!!!!!!!!!

Hi John,

My path up through "A" school was through the Radar branch (I was the
only ETR2 in the Communications Branch when I taught there). The
Radar training gave us hands on experience with equipment that
presented both lumped (pulse forming network) AND line (Magic T and
such) designs. Also, reflected POWER was palpably lethal in both
applications. Melodramatic criticism of the fine points in
terminology carried little weight in lab exercises.

Luckily, I had the presence of mind as a student to hie myself into
Frisco to buy Terman's "Electronic and Radio Engineering." The Navy
course of instruction and training manuals so perfectly dove-tailed to
that book that the fit was a precision match. The "A" school syllabus
didn't go nearly to the depth of detail as offered by Terman (the
ET1&2 and ETC course work did), but it did heavily touch every chapter
found in that tome.

Insofar as heresy, the syllabus was rife with it. We taught that
antennas that were too short could be made to appear longer by the
addition of the "missing" wire in the form of a coil. Similarly, a
too long antenna could be reduced in length by inserting a capacitor.
The teaching aid was to think of the coil symbol as a spring that
could be stretched to lengthen the short antenna, and cap symbol as
providing space enough between the plates to collapse the extra length
of a too long antenna. Clearly the metaphors wheeze, but are
effective well beyond mathematical proofs that could only serve as
sleeping pills.

Before the purists roll their eye's and mutter "tut-tut" under their
beards - instruction was complete to point out these were short-cuts
as memory aides and did not serve as a complete discussion on the
topic. Reflected power certainly fell into that category as its
hazard was positively destructive and not a mental exercise subjected
to debate in a perfumed symposium.

Anyone with radar experience can fashion the plumbing to steer
reflected power to any load. -um- reflected energy be damned at that
point as any reflection was inherently returning to a source that was
long dormant (in terms of microseconds) and ready to dissipate
anything that came down the pipe. The whole point of the magnetron's
success in war was its robustness in the face of catastrophic
mismatches. The PFN might flame out or the thyratron burst, but the
magnetron would survive.

73's
Richard Clark, KB7QHC

question about wire antenna and tuner
 

Sal M. Onella wrote:
Does a T tuner cancel some of the reactance of the line in which it is
inserted, thereby effectively shortening the line.
Am I onto something or have I simply launched myself into the eye of
another ****storm?

A single series length of transmission line can only
transform impedances to other values located on the
SWR circle (or spiral) on a Smith Chart. There is
only one low resistance value on that SWR circle
and it is equal to Z0/SWR. For instance, if the
SWR is 9:1 on 450 ohm line, that value is 450/9 =
50 ohms. If the SWR is 4.5:1, that low resistive
value is 450/4.5 = 100 ohms. If the SWR is 18:1,
that low resistive value is 450/18 = 25 ohms. Only
one value of SWR (9:1) on Z0=450 ohm line will
transform the impedance to 50 ohms. Since my
transceiver is happy with any resistive impedance
between 25 ohms and 100 ohms, I am satisfied with
that maximum 50 ohm SWR of 2:1.

An antenna tuner not only can perform the equivalent
of the above transformation but it can also do the
equivalent of a transformation of the resistance
value to 50 ohms for any SWR within the range of
the tuner. So a tuner can transform 25 ohms or 100
ohms to 50 ohms. A tuner has one more dimension of
matching than does a single series transmission line.

Adding a tapped transformer to a variable length
transmission line system gives it that extra dimension.
A second/third section of transmission line in the
form of a stub will also add that extra dimension.

The main function of matching is to stop reflected
energy from reaching the transmitter leaving it no other
available path except back toward the antenna. That
is done by tuning for a Z0-match at the transmitter. A
tuner is only one way of achieving that Z0-match to
50 ohms.
--
73, Cecil http://www.w5dxp.com

question about wire antenna and tuner
 

The whole point of the magnetron's
success in war was its robustness in the face of catastrophic
mismatches. The PFN might flame out or the thyratron burst, but the
magnetron would survive.

A good thing too, or we would all be eating cold leftovers without
that magic 'radar range'...
Jeez, I still have the original Frigidaire that I bought in the late
60's when I worked for GM - got an employees special deal just in time
for xmas, the first family in our neighborhood to have a radar range,
the neighbors marveled... The kids whipped that puppy day and night...
It has outlived three houses... It has been relegated to my R&D shop
where it happily heats epoxy, paint, putty, and cups of tea with
aplomb... I cannot even begin to guess how many tens of thousands of
times it has been cycled... Dozens of times a day for a quarter
century when the kids were still home...

denny / k8do

question about wire antenna and tuner
 

Ian White GM3SEK wrote:
All valid solutions to the problem of AC/RF generators, transmission
lines and loads will most assuredly comply with the conservation of
energy!

That's a valid assumption since nothing can violate the
conservation of energy principle. But ignoring the
conservation of energy principle under the assumption
that the energy will take care of itself leaves one
ignorant of where the energy goes. If one doesn't know
where the energy goes, that's one's choice, but one
shouldn't turn around and present one's self as an expert
on the subject of where the energy goes. As someone said:
'I personally don't have a compulsion to understand where
this power "goes"', as if understanding might be an
undesirable thing.

But countless textbooks show that it isn't necessary to invoke
that principle in order to make a valid analysis.

It's obvious that you have never perceived the need to
know where the energy goes - that the energy will
automatically take care of itself - and that's perfectly
OK. I, OTOH, have spent considerable time and effort studying
and tracking the energy through the system in order to understand
how the energy balance is achieved and where the energy goes.
So which of us would tend to know more about where the
energy goes?

I have discovered that there is always exactly the amount
of energy in any transmission line needed to support the
measured forward and reflected power. It seems illogical
to me to argue that the energy is somewhere else besides
in the forward and reflected waves.
--
73, Cecil http://www.w5dxp.com

question about wire antenna and tuner
 

"Roy Lewallen" wrote in message
...

snip

And I'm sorry if it ****ed you off. But I hope it made my point:
Observing two things doesn't mean that one causes the other.

If what I posted played any part in helping you -- or other readers --
understand transmission lines even a little better, then it was
worthwhile doing. I know Ian could have done it without ****ing anyone
off, but I'm a lot clumsier with language.

Roy Lewallen, W7EL

Thank you. What you said *was* a help. Maybe without being jolted a bit, I
might not be inclined to dig deeper into the subject. Ham radio covers a
lot of ground -- so much so that digging deeper is always a selective
process.

I've been meaning to get your EZNEC program because it's referenced so often
in this group. This pretty much cinches the deal.

Thanks again.

73,
"Sal"

question about wire antenna and tuner
 

On Tue, 06 Nov 2007 04:32:37 -0800, Denny wrote:

The whole point of the magnetron's
success in war was its robustness in the face of catastrophic
mismatches. The PFN might flame out or the thyratron burst, but the
magnetron would survive.

A good thing too, or we would all be eating cold leftovers without
that magic 'radar range'...
Jeez, I still have the original Frigidaire that I bought in the late
60's when I worked for GM - got an employees special deal just in time
for xmas, the first family in our neighborhood to have a radar range,
the neighbors marveled... The kids whipped that puppy day and night...
It has outlived three houses... It has been relegated to my R&D shop
where it happily heats epoxy, paint, putty, and cups of tea with
aplomb... I cannot even begin to guess how many tens of thousands of
times it has been cycled... Dozens of times a day for a quarter
century when the kids were still home...

denny / k8do

Hi All,

May I come in with some comments from a somewhat different perspective concerning where the reflected power
goes, or where it doesn't go?

Because I'm not particularly adept concerning solid-state tx, this discussion will involve only tube tx with
pi-network output circuits. We'll assume that when the tx has been adjusted to deliver all its available power
into a resistive load, the output resistance appearing at the output terminals of the tx is equal to the load
resistance. For those who may disagree I refer them either to Chapter 19 in Reflections 2, or the May/Jun
issue of QEX, where I report the results of measurements that prove the statement to be true.

Consequently, we'll begin by adjusting the tx to deliver all its available power into a 50-ohm resistive load,
a real 50-ohm physical resistor. Next, we'll change the load to be the input of a 50-ohm lossless transmission
line terminated with a 3:1 mismatched load. What impedance will the tx see? Until we specify the actual load
terminating the line and the electrical length of the line, the tx may see any impedance appearing somewhere
on the 3:1 SWR circle of the Smith Chart. What will happen when the tx sees this mismatched load? First,
because the 3:1 SWR results from a voltage reflection coefficient of magnitude rho of 0.5 (and a power
reflection coefficient of 0.25), this mismatch will cause the tx to reduce its output to deliver only 75
percent of the power delivered into the matched 50-ohm load.

Will the reflected power enter the tx and cause heating? Or will it cause cooling? The answer is that the
reflected power does not enter the tx. So what does happen?

By changing the length of the transmission line at will, we can cause any impedance found on the 3:1 SWR
circle on the Smith Chart to appear at the input terminals of the line. Let's assume the impedance found there
is 50 ohms x 3 equals 150 ohms. This impedance is a lighter load than the original 50-ohm load, so the plate
current will be less than with the 50-ohm load. However, the reflected power did not enter the tx, it only
caused the 150 plus j0.0-ohm impedance to appear at the line input.

Now the important point: The tx would have responded in exactly the same manner if its new load had been a
physical resistor of 150 ohms instead of a 'virtual' resistance of 150 ohms resulting from voltage/current
relationship appearing at the input of the line.

Let's now consider if the line-input impedance is 50/3 ohms, which equals 16.667 ohms. In this case the new
load is lower than the original 50-ohm load, resulting in overloading the tx, causing the plate current to
rise above the rated level, thus causing overheating. But the overheating was caused only by the increase in
plate current resulting from the lowered load resistance, not by reflected power entering the tx. Again, the
same condition would have occurred if a physical resistor of 16.667 ohms had loaded the tx instead of the same
value of virtual resistance appearing at the line input.

Now a third case important to the issue, that in which the impedance appearing at the line input is 50 plus
j57.738 ohms, which also appears on the 3:1 SWR circle. In this case the 57.738 ohms of inductance simply
detunes the pi-network away from resonance, causing plate current to rise, increasing the temperature, but
still reducing the output power to 75 percent of that with the 50-ohm load. And again, precisely the same
result would occur if the new load had been a physical resistance of 50 ohms in series with a physical
57.738-ohm inductor. (It should be obvious that a simple readjustment of the plate capacitor of the pi-network
would return the network to resonance, with the result that the operation of the tx would be identical to that
when loaded with the 50-ohm physical resistor.

The purpose of this commentary is to show that reflected power does not enter the tx, and that the tx cannot
distinguish between a 'virtual' load impedance appearing at the input of a mismatched transmission line and a
physical load comprising a resistor in series with an inductor-the results will be identical in either case.

Walt, W2DU

question about wire antenna and tuner
 

On 7 Nov, 14:30, Walter Maxwell wrote:
On Tue, 06 Nov 2007 04:32:37 -0800, Denny wrote:
The whole point of the magnetron's
success in war was its robustness in the face of catastrophic
mismatches. The PFN might flame out or the thyratron burst, but the
magnetron would survive.

A good thing too, or we would all be eating cold leftovers without
that magic 'radar range'...
Jeez, I still have the original Frigidaire that I bought in the late
60's when I worked for GM - got an employees special deal just in time
for xmas, the first family in our neighborhood to have a radar range,
the neighbors marveled... The kids whipped that puppy day and night...
It has outlived three houses... It has been relegated to my R&D shop
where it happily heats epoxy, paint, putty, and cups of tea with
aplomb... I cannot even begin to guess how many tens of thousands of
times it has been cycled... Dozens of times a day for a quarter
century when the kids were still home...

denny / k8do

Hi All,

May I come in with some comments from a somewhat different perspective concerning where the reflected power
goes, or where it doesn't go?

Because I'm not particularly adept concerning solid-state tx, this discussion will involve only tube tx with
pi-network output circuits. We'll assume that when the tx has been adjusted to deliver all its available power
into a resistive load, the output resistance appearing at the output terminals of the tx is equal to the load
resistance. For those who may disagree I refer them either to Chapter 19 in Reflections 2, or the May/Jun
issue of QEX, where I report the results of measurements that prove the statement to be true.

Consequently, we'll begin by adjusting the tx to deliver all its available power into a 50-ohm resistive load,
a real 50-ohm physical resistor. Next, we'll change the load to be the input of a 50-ohm lossless transmission
line terminated with a 3:1 mismatched load. What impedance will the tx see? Until we specify the actual load
terminating the line and the electrical length of the line, the tx may see any impedance appearing somewhere
on the 3:1 SWR circle of the Smith Chart. What will happen when the tx sees this mismatched load? First,
because the 3:1 SWR results from a voltage reflection coefficient of magnitude rho of 0.5 (and a power
reflection coefficient of 0.25), this mismatch will cause the tx to reduce its output to deliver only 75
percent of the power delivered into the matched 50-ohm load.

Will the reflected power enter the tx and cause heating? Or will it cause cooling? The answer is that the
reflected power does not enter the tx. So what does happen?

By changing the length of the transmission line at will, we can cause any impedance found on the 3:1 SWR
circle on the Smith Chart to appear at the input terminals of the line. Let's assume the impedance found there
is 50 ohms x 3 equals 150 ohms. This impedance is a lighter load than the original 50-ohm load, so the plate
current will be less than with the 50-ohm load. However, the reflected power did not enter the tx, it only
caused the 150 plus j0.0-ohm impedance to appear at the line input.

Now the important point: The tx would have responded in exactly the same manner if its new load had been a
physical resistor of 150 ohms instead of a 'virtual' resistance of 150 ohms resulting from voltage/current
relationship appearing at the input of the line.

Let's now consider if the line-input impedance is 50/3 ohms, which equals 16.667 ohms. In this case the new
load is lower than the original 50-ohm load, resulting in overloading the tx, causing the plate current to
rise above the rated level, thus causing overheating. But the overheating was caused only by the increase in
plate current resulting from the lowered load resistance, not by reflected power entering the tx. Again, the
same condition would have occurred if a physical resistor of 16.667 ohms had loaded the tx instead of the same
value of virtual resistance appearing at the line input.

Now a third case important to the issue, that in which the impedance appearing at the line input is 50 plus
j57.738 ohms, which also appears on the 3:1 SWR circle. In this case the 57.738 ohms of inductance simply
detunes the pi-network away from resonance, causing plate current to rise, increasing the temperature, but
still reducing the output power to 75 percent of that with the 50-ohm load. And again, precisely the same
result would occur if the new load had been a physical resistance of 50 ohms in series with a physical
57.738-ohm inductor. (It should be obvious that a simple readjustment of the plate capacitor of the pi-network
would return the network to resonance, with the result that the operation of the tx would be identical to that
when loaded with the 50-ohm physical resistor.

The purpose of this commentary is to show that reflected power does not enter the tx, and that the tx cannot
distinguish between a 'virtual' load impedance appearing at the input of a mismatched transmission line and a
physical load comprising a resistor in series with an inductor-the results will be identical in either case.

Walt, W2DU- Hide quoted text -

- Show quoted text -

Oh my.All this discussion to help out a newby. So many differences, so
many arguments
it is enough to push a newby away from ham radio.
Let's keep it simple.An antenna is just a pendulum with two energy
storage tanks per cycle.
Each energy tank releases the same amount of energy for the other
energy tank to catch and store before he sends it back.
They call these energy tanks distributed capacitance and inductance
and they are only equal in size
at one wavelength.Anything different from a wavelength and one side
releases more energy
than the other side so you must come to the aid of one side or live
with the consequences of imbalance
which is measured by SWSR, that is the pendulum swings more one way
than the other.
Now you have two energy sources throwing energy at each other ,harder
and harder
such that the transmitter or the onlooking manager starts to get all
sweaty and close to a heart attack.
If the energy sources want to stay on the team and the manager doesn't
want a heart attack then every body shuts down until they find a way
for the pendulum to swing smoothly backwards and forwards in a
friendly manner.
See, antennas are not all that hard to understand if you have the time
to do things right. Forget about photons and reflections which
everybody is arguing about, just make sure that your antenna and
transmitter is happy by keeping the swr down as it is this that
disturbs the operation and nothing more.
Art

question about wire antenna and tuner
 

Art wrote:
"Let`s keep it simple. An antenna is just a pendulum with two energy
storage tanks per cycle."

Not too late for a truth squad to clean up the above, I hope.

I infer from the above that Art implies an antenna to be a resonant
circuit. Many are resonant because a resonant antenna has no net
reactance to impede the signal.

But, there is a non-resonant class of antennas. Antennas in this class
often have radiating conductors terminated at their far ends in their
characteristic resistances (Ro). Traveling waves, reaching Ro which have
not yet been radiated are simply absorbed. There is no reflection and no
standing waves. Up to 50% of the energy fed to the antenna may be wasted
but usually it is somewhat less.

50% waste is a lot, but the directive gain of a typical rhombic may be
50 times according to Fig. 23-18 on page 882 of Terman`s 1955 opus. I`ve
used ountless rhombics and attest that Terman got it right.

Point is, there`s no pendulum up there, only simple wires carrying RF
and they radiate like gangbusters!

Best regards, Richard Harrison, KB5WZI