Reg Edwards wrote:
Cec, I don't doubt your experimental results. It's your extrapolated
imagination and logic which worries me. ;o)

I didn't imagine those experimental results, Reg, and all I did was
report those results. My logic tells me that there is a grain of
valid circumstantial evidence in there somewhere.

What you need to do to prove your point is present an antenna where the
high-current portion is prohibited from radiating yet still yields a
high field strength.

Example #1: The top half of an electrical 1/4WL antenna is prohibited
from radiating by a balanced top hat. Field strength results are
similar to a 1/4WL monopole. This has already been presented.

Example #2: The bottom half of an electrical 1/4WL antenna is
prohibited from radiating by _________________. Fill in the blank
and prove that field strength results are similar to a 1/4WL monopole.
That's all you need to do to make a believer (instead of a doubter)
out of me.
--
73, Cecil http://www.qsl.net/w5dxp



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Its the voltage parts of the antenna which do the radiating.

That is proved by cutting off the top part of the antenna and replacing it
with a top hat which has a much larger capacitance so it radiates the power
harder.
---
Reg.

Cecil Moore wrote:

Reg, we have a clear example of where the high voltage part of the
antenna is not allowed to radiate (much). That would be a balanced
top hat. Not allowing the high voltage part of the antenna to radiate
leaves the high current part to do most of the radiating.

Cecil,

Reg makes a good point. We know that the same amplitude (less ohmic
losses) of current travels the entire length of the antenna in both
directions. The relative phase of forward and reverse currents simply
makes the superposition of the two currents greater at one end than
another. We might measure the standing wave current with an ammeter,
but it is the traveling wave currents which radiate.

73, Jim AC6XG

Jim Kelley wrote:
Reg makes a good point. We know that the same amplitude (less ohmic
losses) of current travels the entire length of the antenna in both
directions. The relative phase of forward and reverse currents simply
makes the superposition of the two currents greater at one end than
another. We might measure the standing wave current with an ammeter,
but it is the traveling wave currents which radiate.

A balanced top hat doesn't radiate much because the currents in the
opposing elements are 180 degrees out of phase with each other. It
doesn't matter if they are traveling waves or standing waves. If they
are 180 degrees out of phase with each other, they are more like a
transmission line than they are like an antenna.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:

Reg, we have a clear example of where the high voltage part of the
antenna is not allowed to radiate (much). That would be a balanced
top hat. Not allowing the high voltage part of the antenna to radiate
leaves the high current part to do most of the radiating.

Cecil,

Reg makes a good point. We know that the same amplitude (less ohmic
losses) of current travels the entire length of the antenna in both
directions. The relative phase of forward and reverse currents simply
makes the superposition of the two currents greater at one end than
another. We might measure the standing wave current with an ammeter,
but it is the traveling wave currents which radiate.

73, Jim AC6XG

============================

Jim, are you one of the crackpots who think that it's the voltage parts of
the antenna which do the radiating which is proved by replacing the top
portion of the antenna with a top hat which has a large capacitance so that
the voltage has a greater effect. ;o)
---
Reg, G4FGQ

Reg Edwards wrote:

Cecil Moore wrote:

Reg, we have a clear example of where the high voltage part of the
antenna is not allowed to radiate (much). That would be a balanced
top hat. Not allowing the high voltage part of the antenna to radiate
leaves the high current part to do most of the radiating.

Cecil,

Reg makes a good point. We know that the same amplitude (less ohmic
losses) of current travels the entire length of the antenna in both
directions. The relative phase of forward and reverse currents simply
makes the superposition of the two currents greater at one end than
another. We might measure the standing wave current with an ammeter,
but it is the traveling wave currents which radiate.

73, Jim AC6XG

============================

Jim, are you one of the crackpots who think that it's the voltage parts of
the antenna which do the radiating which is proved by replacing the top
portion of the antenna with a top hat which has a large capacitance so that
the voltage has a greater effect. ;o)
---
Reg, G4FGQ

Hi Reg,

Were it not for this group, I would never have known the full extent of
my crackpottedness! My colleagues and associates have been keeping it a
secret from me all these years evidently. With that in mind, yes.
Nevermind Farady. The size of the hat should indeed determine the size
of the effect. I wear a 7 3/4.

73, Jim AC6XG

Reg, G4FGQ wrote:
"One old wife asserts it is obvious radiation occurs mainly from the
middle portion of a dipole because that is where the current is
strongest and the magnetic field is most concentrated."

All sections of a dipole are needed to establish the wave launcher /
grabber.

Seems to me the old wife quoted above is right. Radiation from a dipole
is concentrated in a doughnut pattern around the middle of the wire.

What influences are sensed at a distance point perpendicular to the
middle of the dipole?

There are electric fields, plus and minus, which cancel.

The current on one side of the dipole flows into the source while the
current on the other side of the source flows out. This places current
on both sides of the dipole in the same direction.

The magnetic fields from both sides of the dipole are additive because
the currents producing them are in-phase.

Never mind that an electromagnetic wave must have an electric field as
well as a magnetic field. The emerging magnetic field generates an
electric field which generates a magnetic field ad infinitum.

Best regards, Richard Harrison, KB5WZI

On Thu, 11 Mar 2004 08:38:07 -0600 (CST),
(Richard Harrison) wrote:

Seems to me the old wife quoted above is right. Radiation from a dipole
is concentrated in a doughnut pattern around the middle of the wire.

Hi Richard,

This is from an infinite perspective where all contributions of
radiation sum to form the shape you describe. If you were actually
sitting at the middle of that "doughnut" you would see a pattern more
like three poached eggs bigger than the size of the structure.

Examples of near field patterns (evidenced through their imposition of
a Z other than 377 Ohms upon the vicinity of the antenna) may be
observed at:
http://home.comcast.net/~kb7qhc/ante...elds/index.htm
with:
http://home.comcast.net/~kb7qhc/ante...pole/index.htm
showing a distinct activity at BOTH the middle AND at the ends.

73's
Richard Clark, KB7QHC