On Thu, 3 Jan 2008 20:56:02 -0500, "AI4QJ" wrote:

Jim's question is answered quite simply and you have offered one
yourself, generously slathered with doubt about its obvious
application.

However, my guess finds the symptoms would be more aligned with two
current nodes, not voltage. However, voltage or current, either mock
the notion of "traveling waves," as Cecil recoils in shock from the
bitter reality (his bête noire when it fails to serve his agenda) of
this contradiction.

No it doesn't. As soon as heat is dissipated, then we know that there is a
real power component where current is in phase with voltage.

Hi Dan,

That stands to reason.

I think in this
case the insulating material broke down due to high voltage.

However, that does not. You (and I) don't have enough information
(not that it matters in confounding Cecil).

The reason is
that, with an unterminated coax, the reflected wave adds to the forward wave
only at those portions of the line where the standing wave was at maximum
and minimum.

This is rote (aside from the rough and loose description).

If the linear amp had a forward component at Vmax = 6KV, then
the standing wave maximum and minimum would be +12KV and -12KV.
and this is the particular information neither of us has. How do you
know Jim was running a linear, much less resulting with that
particular voltage? The clipped voltage commentary is strictly
conjecture.

Your theory on the other hand, though possible, is lees likely in an amateur
environment. The reason is that even a 22 AWG conductor can withstand a
rather large amount of current before it gets so hot as to melt and damage
the thermoplastic insulation.

Fusing current for 22 AWG runs about 40A in ambient temperature. The
inner core is not in ambient, but rather it is insulated (as you well
testify), which lowers the current required to open it. We don't need
fusing current but it does establish a rather dramatic caloric upper
limit that easily exceeds the capacity of plastic to sustain exposure
to the obvious heat. It is enough to say that lower currents could
easily melt the plastic without having to "blow the fuse" so-to-speak.

All that remains is additional information from Jim as to the physical
clues of melting or carbonization. With thermal runaway a distinct
probability, both probably occurred and it is then a chicken and egg
problem. The wavelength distance of these burns from the open end
will nail it down with far more assurance than anecdotal evidence.

It relates to another bitter round in his own thread of trying to
explain the confusion Hams have with Rhombic antennas and traveling
waves to then discover standing waves line up and down them:

In any antenna, you will have a combination of standing waves and traveling
waves.

It took me only one post to prove that with data. I am not
responsible for Cecil's framing of the argument to the contrary. Most
of Cecil's craft projects contain critical errors that collapse his
argument into wandering statements. To this point of 400 postings, or
so, absolutely no one has expressed any confusion that Cecil implied
was his premise to explain in the original thread. His straw man
kneed him in the groin before he could get in his first argument and
the gasps of incredulity were his own. :-)

What I was saying was, in the above example, even if you started out
with an open coax line and a perfect standing wave where no real power was
dissipated, immediately after the insulation broke dow real power started
dissipating and that component could only be composed of travelling waves,
in phase with current and voltage.

It isn't that difficult, complex, or messy. All of this embroidery is
like a traffic cop stopping you for speeding, and citing your
violation in terms of galactic spin (tracking you at an even speed is
vastly simpler and both you and the judge would be forced to agree
that, yes, you were speeding).

73's
Richard Clark, KB7QHC

Richard Clark wrote:
"AI4QJ" wrote:
In any antenna, you will have a combination of standing waves and traveling
waves.

It took me only one post to prove that with data. I am not
responsible for Cecil's framing of the argument to the contrary.

I fail to see what Richard thinks he has proven except
that he disagrees with Balanis, Kraus, and Jasik. It
is obvious that a lot of people don't understand the
considerable difference between standing waves and
traveling waves on an antenna or on transmission lines.

Although every real-world antenna contains both standing
waves and traveling waves, a 1/2WL dipole is classified as
a standing-wave antenna and a terminated rhombic is
classified as a traveling-wave antenna. Anyone who is
interested can model those two antennas using EZNEC to
observe the considerable difference in the antenna
currents.

Balanis dedicates most of "Antenna Theory", Chapter 10,
Traveling Wave and Broadband Antennas", page 488, 2nd
edition, to traveling-wave antennas like the terminated
Beverage and rhombic.

Also from "Antennas" by Kraus & Marhefka, 3rd edition:
"The condition of a uniform traveling wave on an antenna
is one of considerable importance, as this condition may
be approximated in a number of antennas systems." He
talks about terminated Beverage and rhombic antennas as
examples of traveling-wave antennas.

Jasik says: "Practically all standing-wave long-wire
antennas have gone out of use with preference for the
traveling-wave types." He then discusses the terminated
rhombic as an example of a traveling-wave antenna.
--
73, Cecil http://www.w5dxp.com

AI4QJ wrote:
I think in this
case the insulating material broke down due to high voltage.

J. C. Slater agrees with you. In "Microwave Transmission",
he wrote: "Particularly in coaxial lines, the limit to the
possible transmitted power is generally set by difficulties
of corona or sparking between the two conductors of the line.
The greatest practical reason for avoiding reflections is to
reduce the magnitude of these voltage maxima."
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Richard Clark wrote:
"AI4QJ" wrote:
In any antenna, you will have a combination of standing waves and
traveling waves.

It took me only one post to prove that with data. I am not
responsible for Cecil's framing of the argument to the contrary.

From The IEEE Dictionary:

"traveling-wave antenna - An antenna whose excitation
has a quasi-uniform progressive phase, as the result
of a single feeding wave traversing its length in
one direction only."

Here are some more quotes from The ARRL Antenna Book:
"All the antenna systems considered so far in this
chapter have been based on operation with standing
waves of current and voltage along the wire. ..."

It then describes the concept of a terminated antenna
and says: "In such an antenna there are no standing
waves, because all received power is absorbed at
either end." The terminated rhombic antenna is then
described.

About Beverage antennas: "Because the Beverage is a
traveling wave, terminated antenna, it has no standing
waves resulting from radio signals."
--
73, Cecil http://www.w5dxp.com

On Jan 2, 7:47*pm, "AI4QJ" wrote:
"Roy Lewallen" wrote in message

...

Jim Kelley wrote:

I have a piece of coax around here somewhere that I once burned up. *I
recall telling you about it. *The insulation is bubbled and melted at
half wavelength intervals. *Please explain what particular aspect of a
traveling wave might have caused that to happen.

It's the consequence of having *two* traveling waves, which occurs any
time the line isn't terminated with its characteristic impedance. Betcha
yours wasn't.

As you have stated before, the standing wave is the ENVELOPE of maxima
resulting from forward and reflected waves. The ENVELOPE maxima and minima
will occur at 1/2WL distances in the cable. If the line is lossless, no
power is consumed in the unterminated line.

If *I were to see a cable with melted insultion at 1/2 wavelengths and the
coax was open, the first thing I would suspect is that the voltage on the
inner conductor greatly exceed the dilectric strength of the insulation
between inner conductor and shield at the original standing wave maxima and
minima. Two 3-500Z's in series could produce 6KV or even more. Standard
Radio Shack grade RG58 might not be able to handle that. When the insulation
breaks down it turns into a carbon resistor and we no longer have a lossless
situation; real power is dissipated. Whther or ot the standing wave is still
present, power will dissipate where the dielctric material has turned into
carbon (even with DC). Less likely would be current heating the inner
conductor, again a resistive power loss. But these discussions have been
assuming a lossless line of infinite dielectric strength where real power
disspiation cannot occur unless we terminate the line and only then, in the
terminating component since the line is supposedly 'lossless'. Adding the
real life burnt coax example when the discussion assumes ideal components is
comparimg apples and oranges; all we are doing is exposing the weakness of
the assumption when using ideal lossless components. BTW, in any case in
which insulation melting occurs and we have deviated from the ideal
transmission line, at least some of the reactive power that was contained in
the standing wave has now been changed into a travelling wave with I/V in
phase thru the 'resistors' between inner conductor and shield.

This is the discussion I was hoping Cecil would take up. I can assure
you that the coax I was using was not lossless; RG58 is quite real in
that respect. The source was probably good for a kilowatt at 2.4 GHz,
though it's likely only a small fraction of that was actually coupled
from the cavity by Langmuir probe into a 50 ohm termination of some
sort. (This was 20 years ago, so some of the details have faded
now.) The cable got hotter than a firecracker in a very short period
of time over centimeter sized regions spaced some number of
centimeters apart. The coax appeared to have melted due to excessive
I^2R heating by the conductors. Skin effect apparently played no
small role. I believe the voltage in question is not the voltage
across the dielectric, but rather along the conductor. At my
suggestion the experiment was not repeated. :-)

73, ac6xg

On Fri, 04 Jan 2008 00:40:23 -0600, Cecil Moore
wrote:

Here are some more quotes

Dragging more bones out of the crypt and calling them USDA Prime Rib.

About Beverage antennas: "Because the Beverage is a
traveling wave, terminated antenna, it has no standing
waves resulting from radio signals."

Well, that explains a Rhombic to clear up everyone's confusion! Gee,
Mr. Peabody, let's step into the "Way-Back machine" and find us an
example of this Beverage antenna!

I suppose this example would be either too real, and unrepresentative
of our Guru's pronouncements of RF purity;

OR

I suppose this example would be too text book, and unrepresentative of
our Guru's pronouncements of RF reality.

Gad, was is a loathsome degenerate like me suppose to do when faced
with a dilemma like this? I mean, damned if you do one, and damned if
you do the other.

The only choice is to use one of Cecil's designs and see what Cecil
would pop an aorta over.

So, with that in mind, I simply step into the Way-Back machine and
crank in Tue, 18 Dec 2007 09:33:23 -0600, Cecil Moore
wrote:
The traveling-wave file is:

http://www.w5dxp.com/TravWave.EZ

It has already been demonstrated that it is inferior in design, but in
full faith to the original designer's intent of exhibiting a traveling
wave, I must stoop to accept less for the sake of embracing its
lineage (shudder).

Dear readers, we must take care not to upset the harmony of the
crystal spheres of our esteemed Guru of the Airwaves; however, fashion
dictates that the most recent withdrawal from the vaults above demand
an external radio signal, not one driving his divine inspiration. As
always, the best way to confound Cecil is to embrace his own work.
So, by the simple addition of ONE WIRE, 60 feet tall and located
100,000 feet away (we can't be bothered with interactions polluting
this study) we then shift the source to this distant radio to see what
currents are pressed upon the receiving antenna (as is such the
obvious destiny of the Beverage).

SWR along the length of the line: 8:1

Hmm, must be the charm of the original designer that so pollutes those
ancient tomes exposed to the cold cathode light of the Xerox. This
shocking result is certainly not the product of original thinking.

At this juncture, dare I attempt something more conventional? After
all, the Beverage is classically taller than Cecil's one foot tall
munchkin. It also resides over real ground, which, after all, is the
classic ingredient to its success. Having embraced damnation in using
Cecil's I can't be burned in purgatory for any more normal design.

So, let's see what appears on the radio from designs that are more
classic.

This time we have a 1000 meter long wire 3 meters above ground;
100,000 meters away is our transmitter;
we are operating on 3.8MHz;
the load of 600 Ohms is placed against a radial system below it;
there are 16 radials, each only 4 meters long, 1 centimeter above
real, high accuracy ground.

We turn on the transmitter, and look at the SWR due to currents
reported:
8:1 SWR at the transmitter end with the current phase swinging
like a pendulum. With something like 300 segments, that is
roughly a 18 degree shift per segment along the wire (Cecil's
forecast was 0) over a continuum of 360 degrees (cycle repeats
every 20 segments like clock work).

No doubt this unfortunate pair of designs (the prince and the pauper)
will evoke calumny and rage against this miserable churl for presuming
to interpret the mystic arts known only to the Gurus.

Another explanation might be that Traveling waves means something
altogether different than how they are commonly discussed on this
board. Perhaps the Xerox will reveal that nuance. Maybe it is a
threshold issue. The Guru need only climb the mount for more tablets
of scripture to render:
"All SWR less than 2:1 is henceforth decreed by holy writ
to be flat and conforming to the ecumenical standards of
Traveling Waves - so has it been said, so shall it ever be!"

73's
Richard Clark, KB7QHC

wrote:
This is the discussion I was hoping Cecil would take up.

I did take it up. Power was dissipated in the process
of destroying the coax. There is zero real power in standing
waves. Therefore, standing waves did not destroy the
coax. By the process of elimination, it was traveling
waves that destroyed the coax. The failure of the coax
caused the system to shift into the transient state
thus changing the standing waves to traveling waves
which delivered the power to destroy the coax.

During the initial transient state, traveling wave
energy becomes standing wave energy that exists
through steady-state. During the final transient
state, that steady-state standing wave energy is
released back to traveling wave energy and dissipated
or radiated. During the failure of the coax, standing
wave energy becomes traveling wave energy once again
which delivered the power to destroy the coax.

J. C. Slater says it is more likely that the damage
occurred at the current nodes rather than at the
voltage nodes.
--
73, Cecil http://www.w5dxp.com

Richard Clark wrote:
http://www.w5dxp.com/TravWave.EZ

It has already been demonstrated that it is inferior in design,

It is not an antenna - it is a wire that demonstrates
traveling waves by eliminating reflections.

We turn on the transmitter, and look at the SWR due to currents
reported:
8:1 SWR at the transmitter end with the current phase swinging
like a pendulum. With something like 300 segments, that is
roughly a 18 degree shift per segment along the wire (Cecil's
forecast was 0)

Sorry, Richard, that is a false statement. With traveling wave
antennas, there is a phase shift per segment. An antenna with
an SWR of 8:1 is neither a traveling-wave nor a standing-wave
antenna but is a hybrid between the two. As usual, you have
either confused yourself or are trying to confuse others.
Sometimes it is hard to tell which.

A 1/2WL dipole is a standing-wave antenna with an SWR ~20:1
on the antenna wire. Take a look at its current phase.

A traveling-wave antenna needs an SWR close to ~1:1 to be
a good example. Whether by accident or on purpose, yours
is a very poor example.
--
73, Cecil http://www.w5dxp.com

On Fri, 04 Jan 2008 13:59:55 GMT, Cecil Moore
wrote:

A 1/2WL dipole is a standing-wave antenna with an SWR ~20:1
on the antenna wire.

Now there's an original observation.

A traveling-wave antenna needs an SWR close to ~1:1 to be
a good example. Whether by accident or on purpose, yours
is a very poor example.

I used your Traveling Wave antenna. :-

We can both agree the data reveals the truth of it being a very poor
example.

Dear Readers.

This was another slam-dunk. It was easier than collecting
unemployment. The simplest part is using Cecil's own examples and
drilling into their fault seams. Like this one, they usually split
open and spill their contents like an overripe watermelon.

It is unlikely that any better example will arrive that bears any
resemblance to what Beverage designed, so the data once again goes
undisputed in confounding the Guru of the Airwaves.

Richard Clark wrote:
A traveling-wave antenna needs an SWR close to ~1:1 to be
a good example. Whether by accident or on purpose, yours
is a very poor example.

I used your Traveling Wave antenna. :-

http://www.w5dxp.com/TravWave.EZ

Good grief, Richard! You cannot use the 8.4:1 50 ohm SWR
reading for the SWR on a wire with a characteristic
impedance of 411 ohms. I see what you did now and it
is was more than stupid.

The load resistor is 411 ohms. The characteristic impedance
of the wire is close to 411 ohms. Set the Alt SWR Z0 to
411 ohms and observe the actual SWR of 1.025:1.

The SWR is 1.025:1. The current on the wire is close to
100% traveling wave current. You observed the phase shift
and reported it. You have proved my point while trying
to discredit it. Thank you very much.

The reason that I didn't defend myself against what you
were saying is that I didn't believe anyone would be
so stupid as to report the 50 ohm SWR on a wire with
a characteristic impedance of 411 ohms. Therefore, I
didn't know you were talking about my example.
--
73, Cecil http://www.w5dxp.com