Gene Fuller wrote:
I cannot speak directly for Tom Donaly, but you and I are about 99% in
DISagreement over physics.

That's just a straw man, Gene. You school and my school probably
taught 99% the same physics. You and I are not that far apart at
all. THERE ARE NO CONTRADICTIONS BETWEEN THE PHYSICS YOU USE AND
THE CONCEPTS I AM PRESENTING. It only appears that way to you
because you haven't taken the time to understand those concepts.

Are there standing waves on a standing wave antenna? Are standing
waves caused by the superposition of forward and reflected waves?
Absolutely nothing new or different there.

Current, charge, voltage, E-field, and H-field are different physical
entities. They are related, but they are not interchangeable.

Straw man alert! I resent any implication that I said they were
interchangeable. I agree with you about the above quantities.

No amount of E-field, H-field, or voltage can create or destroy charge.

Straw man alert! I resent any implication that I said charge could
be destroyed. I agree with what you said about charge.

Current is the movement of charge. At any point in space that charge
must either keep moving (Kirchhoff's current law) or it must be stored
(continuity equation). There is absolutely no other choice, period.

EXACTLY! And that is exactly what you and W8JI are missing. The familiar
cosine current distribution on a dipole is a standing wave, i.e. the net
current in that standing wave is not moving. Therefore, the net current
doesn't obey your rules above. The net current is just an artifact of
superposition of the forward current wave with the reflected current
wave. It is the forward current and reflected current that is moving.
Until you and Tom understand the nature of standing-wave antennas, you
will never understand the nature of the current(s) through a loading
coil installed in the middle of a standing wave antenna.

Kurt N. Sterba made the same mistake in this month's Worldradio article.
In a standing-wave antenna, the net current doesn't flow and RF current
cannot stand still. The current is zero at the tip of a standing wave
antenna not because all the energy has been radiated and/or conducted
away by displacement currents. The current is zero because all the
energy at that point is contained in the E-field. The forward H-field
and the reflected H-field cancel each other at the tip of a standing
wave antenna. If you really think there is zero energy at the tip of
a mobile antenna, please grab it while power is applied.

Your traveling wave/standing wave model is intuitive, but otherwise
useless.

Until you take the time to conceptually understand standing wave
antennas, there is absolutely no chance of you understanding what
happens when a loading coil is inserted in a standing wave antenna.

If so, then it is likely
that Balanis is merely trying to tie the entire world of antennas
together to give a warm and fuzzy feeling to the reader.

If what Balanis said is false, please present some proof.

Do you have a reference to an analytic treatment using the traveling
wave model that could give results comparable to NEC2? If so, I would
sure like to find that reference.

There are some problems that do not lend themselves very well to a
quantitative analysis. That's why simulation modeling is so popular with
antennas and Blackjack.

However, the difficulty of a quantitative analysis should not turn your
brain into concrete such that you reject the associated qualitative
analysis. All of these qualitative concepts are presented in textbooks.
I have only quoted a handful of them.
--
73, Cecil, W5DXP

Cecil,

There is complete contradiction between the physics you have concocted
and the real world.

I perfectly understand your concepts. They are great for explanations
and handwaving, but little else.

Until you understand the basics of the first few chapters in any physics
(E&M) textbook there is no hope for agreement. Little more for me to say.

73,
Gene
W4SZ

Cecil Moore wrote:
Gene Fuller wrote:

I cannot speak directly for Tom Donaly, but you and I are about 99% in
DISagreement over physics.


That's just a straw man, Gene. You school and my school probably
taught 99% the same physics. You and I are not that far apart at
all. THERE ARE NO CONTRADICTIONS BETWEEN THE PHYSICS YOU USE AND
THE CONCEPTS I AM PRESENTING. It only appears that way to you
because you haven't taken the time to understand those concepts.

Are there standing waves on a standing wave antenna? Are standing
waves caused by the superposition of forward and reflected waves?
Absolutely nothing new or different there.

Current, charge, voltage, E-field, and H-field are different physical
entities. They are related, but they are not interchangeable.


Straw man alert! I resent any implication that I said they were
interchangeable. I agree with you about the above quantities.

No amount of E-field, H-field, or voltage can create or destroy charge.


Straw man alert! I resent any implication that I said charge could
be destroyed. I agree with what you said about charge.

Current is the movement of charge. At any point in space that charge
must either keep moving (Kirchhoff's current law) or it must be stored
(continuity equation). There is absolutely no other choice, period.


EXACTLY! And that is exactly what you and W8JI are missing. The familiar
cosine current distribution on a dipole is a standing wave, i.e. the net
current in that standing wave is not moving. Therefore, the net current
doesn't obey your rules above. The net current is just an artifact of
superposition of the forward current wave with the reflected current
wave. It is the forward current and reflected current that is moving.
Until you and Tom understand the nature of standing-wave antennas, you
will never understand the nature of the current(s) through a loading
coil installed in the middle of a standing wave antenna.

Kurt N. Sterba made the same mistake in this month's Worldradio article.
In a standing-wave antenna, the net current doesn't flow and RF current
cannot stand still. The current is zero at the tip of a standing wave
antenna not because all the energy has been radiated and/or conducted
away by displacement currents. The current is zero because all the
energy at that point is contained in the E-field. The forward H-field
and the reflected H-field cancel each other at the tip of a standing
wave antenna. If you really think there is zero energy at the tip of
a mobile antenna, please grab it while power is applied.

Your traveling wave/standing wave model is intuitive, but otherwise
useless.


Until you take the time to conceptually understand standing wave
antennas, there is absolutely no chance of you understanding what
happens when a loading coil is inserted in a standing wave antenna.

If so, then it is likely that Balanis is merely trying to tie the
entire world of antennas together to give a warm and fuzzy feeling to
the reader.


If what Balanis said is false, please present some proof.

Do you have a reference to an analytic treatment using the traveling
wave model that could give results comparable to NEC2? If so, I would
sure like to find that reference.


There are some problems that do not lend themselves very well to a
quantitative analysis. That's why simulation modeling is so popular with
antennas and Blackjack.

However, the difficulty of a quantitative analysis should not turn your
brain into concrete such that you reject the associated qualitative
analysis. All of these qualitative concepts are presented in textbooks.
I have only quoted a handful of them.
--
73, Cecil, W5DXP

Richard Harrison wrote:

"A wire antenna is a circuit with distributed constants;

Terman, Kraus, Balanis, ... what do they know? :-)

Apparently, a lot of the otherwise knowledgeable people
on this newsgroup have forgotten that the formula for
the characteristic impedance of a single-wire transmission
line is 138*log(4h/d) where h is the height of the wire
above ground and d is the diameter of the wire. There's
no difference between that single-wire transmission line
and a lot of ham antennas. That single-wire transmission
line radiates just like an antenna.

1/2WL of #16 wire 24 feet in the air has a Z0 of 600 ohms.

If that center-fed dipole were terminated at each end with
a 600 ohm load, it would be a traveling-wave antenna with
a feedpoint impedance of 600 ohms. Take away the loads and
there's a match to 50 ohm coax at the feedpoint.

The only difference in those two antennas is that removing
the loads turned the antenna into a standing-wave antenna
and reflections are arriving back at the feedpoint, lowering
the feedpoint impedance.

Any coil installed in a standing wave antenna is going to
be subjected to both forward and reflected currents. There
is no hope of understanding the current in a loading coil
without understanding the component currents flowing both
directions through the loading coil.
--
73, Cecil, W5DXP

Gene Fuller wrote:
Nothing I wrote conflicts with Terman or Balanis.

And nothing I wrote conflicts with your physics.
--
73, Cecil, W5DXP

Richard Cl;ark wrote:
"The radiation resistance of an antenna is NOT necessarily the same as
the drivepoint impedance of the antenna."

True, but for many resonant antennas they are identical.

Fundamentally, the radiation resistance is the value when inserted in
series with an antenna will consume the same power as that radiated.
Unless otherwise specified, the radiation resistance is referred to a
current maximum point in an ungrounded antenna, and to the base of a
grounded antenna. See 1955 Terman page 890 and 1950 Kraus page 143. They
agree.

All of ON4UN`s loaded antennas have maximum current at their drivepoints
and they are resonant, so their feedpoint resistance coincides with
their radiation resistance in all the instances diagrammed in the
current distribution chart for short loaded verticals. ON4UN starts with
1A current to the base of all antennas and the current declines from
that value. Its value is the cosine of the number of degrees from the
feedpoint in most cases.

Best regards, Richard Harrison, KB5WZI

Gene Fuller wrote:
There is complete contradiction between the physics you have concocted
and the real world.

That's simply a false statement and your agenda seems to
be personal rather than technical. Whose sacred cow am
I goring?

I say there are standing waves on a standing wave antenna.
You disagree "completely" with everything I say. So, Gene,
please prove that standing waves are absent on a standing
wave antenna. After that, please explain why they are
called "standing wave" antennas. Also explain why you
think Terman, Kraus, and Balanis are wrong in their
explanations of how standing waves exist on standing
wave antennas.
--
73, Cecil, W5DXP

On Thu, 4 Nov 2004 14:03:59 -0600, (Richard
Harrison) wrote:

All of ON4UN`s loaded antennas have maximum current at their drivepoints
and they are resonant, so their feedpoint resistance coincides with
their radiation resistance in all the instances diagrammed in the
current distribution chart for short loaded verticals.

Hi Richard,

My point is that this does not follow. The drivepoint Z is NOT the
"radiation resistance" irrespective of loading transformation. You
can build a very small radiator, load it to resonance and it offers
extremely poor efficiency. Examples abound.

73's
Richard Clark, KB7QHC

Arguing about the "true" meaning of radiation resistance is pointless.
If you'll look through various respected texts and references, you'll
see that it's used by different authors in different ways. (I posted
some specific examples quite a long time ago on this newsgroup -- I'll
find and repost if anyone is interested.) Some authors refer it to a
current loop; others use it to describe the feedpoint resistance, at
resonance or not. In "folded" antennas, it can mean either the
"unfolded" resistance or the transformed feedpoint resistance. The only
common thread in usage is that it always represents a sink for the power
which is radiated, so this is the only "true" meaning of the term. The
greatest danger in being careless about usage is in blindly using some
formula such as a common one for efficiency, Efficiency = Rr / (Rr +
Rl). This works only if Rr and Rl are referred to the same point. For
example, if used for a folded dipole or unipole, both Rr and Rl must be
as measured at the feedpoint, where they're both transformed by the
"folding" process; or both defined as properties of the unfolded
antenna. Using the "folded" value of one and "unfolded" value of the
other leads to incorrect conclusions about efficiency -- conclusions
which been successfully used to sell antennas.

A given antenna doesn't have a single "inherent" or "fundamental" value
of radiation resistance -- it's different at every point along an
antenna, and the term can be legitimately used to describe the radiation
"loss" component at any point. So whenever there's a chance of
misunderstanding, it's important to say exactly what you mean by
"radiation resistance" -- that is, where on the antenna this equivalent
resistance is -- whenever you use the term.

Roy Lewallen, W7EL

Richard Harrison wrote:
Richard Cl;ark wrote:
"The radiation resistance of an antenna is NOT necessarily the same as
the drivepoint impedance of the antenna."

True, but for many resonant antennas they are identical.

Fundamentally, the radiation resistance is the value when inserted in
series with an antenna will consume the same power as that radiated.
Unless otherwise specified, the radiation resistance is referred to a
current maximum point in an ungrounded antenna, and to the base of a
grounded antenna. See 1955 Terman page 890 and 1950 Kraus page 143. They
agree.

All of ON4UN`s loaded antennas have maximum current at their drivepoints
and they are resonant, so their feedpoint resistance coincides with
their radiation resistance in all the instances diagrammed in the
current distribution chart for short loaded verticals. ON4UN starts with
1A current to the base of all antennas and the current declines from
that value. Its value is the cosine of the number of degrees from the
feedpoint in most cases.

Best regards, Richard Harrison, KB5WZI

Richard Clark wrote:
The drivepoint Z is NOT the
"radiation resistance" irrespective of loading transformation. You
can build a very small radiator, load it to resonance and it offers
extremely poor efficiency.

The ARRL Antenna Book says the feedpoint impedance of an
8 foot center-loaded mobile antenna on 80m is 22 ohms
while the radiation resistance is 0.8 ohms.
--
73, Cecil, W5DXP

The ARRL Antenna Book says the feedpoint impedance of an
8 foot center-loaded mobile antenna on 80m is 22 ohms
while the radiation resistance is 0.8 ohms.

=====================================
Cec,

There you (in the plural) go again - using handbooks as bibles.

Written by technically ill-educated amateurs and professionals, no different
from yourselves, who can't agree on ANYTHING beyond V=I/R.

These threads sure have entertainment value. Not quite hilarious, too
serious, but well worth a speed-read, ;o)

Cec, I'm on deep red, South African Western Cape, Pinotage-Shiraz tonight.
You should try some. Makes a change from Californian, Texan and John Wayne,
six-shooter politics.
----
Yours, Reg, G4FGQ