On Wed, 10 Mar 2004 14:34:38 -0600, Cecil Moore
wrote:

Reg Edwards wrote:
Cec, who's Jerry Sevick. I don't seem to have a copy of his works around me
at present.

He's accepted by most as *the* ham balun guru. Some disagree.

Yeah, I'm one who disagrees!

Walt, W2DU

He's accepted by most as *the* ham balun guru. Some disagree.
======================

How can anybody make himself a guru about such a simple, inactive, mundane
device as a balun?

Now if it was a conjugate match!

Walter Maxwell wrote:

Cecil Moore wrote:
He's accepted by most as *the* ham balun guru. Some disagree.

Yeah, I'm one who disagrees!

Well, wait until you find out exactly what the disagreement was.
I said a balanced set of elevated radials or a balanced top hat
doesn't radiate much RF. What do you say?
--
73, Cecil http://www.qsl.net/w5dxp



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On Wed, 10 Mar 2004 22:57:01 GMT, Walter Maxwell wrote:

|On Wed, 10 Mar 2004 14:34:38 -0600, Cecil Moore
|wrote:
|
|Reg Edwards wrote:
| Cec, who's Jerry Sevick. I don't seem to have a copy of his works around me
| at present.
|
|He's accepted by most as *the* ham balun guru. Some disagree.
|
|Yeah, I'm one who disagrees!

But he is certainly prolific. Can't pick up a magazine without
another same-o-same-o article. Latest in Feb. "High Frequency
Electronics."


Wes

Walter Maxwell wrote:
Have you guys ever considered that since the infinitesimally short dipole
radiates only 4 percent less than a resonant dipole, the only reason for having
any longer length than infinitesimally short is to make it resonant?

The total field radiated should be proportional to the product of the
voltage and the current applied to the radiator. The size and shape of
the radiator will determine the impedance and radiation pattern.
Neither issue speaks to the "exact location of the point of max
radiation". Any point along the radiator in which traveling wave
currents are flowing will radiate. The amount of radiation emanating
from any given point would be proportional to the rate at which energy
traverses that point.

Does
that bring to mind whether the max radiation occurs at the max voltage or max
current portion of the dipole?

The existance of a max radiation point along a radiator should first be
shown before we begin to argue about its exact location. In my opinion.

73, Jim AC6XG

"Walter Maxwell" wrote in message
...
On Wed, 10 Mar 2004 13:43:05 -0800, Jim Kelley wrote:

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

Have you guys ever considered that since the infinitesimally short dipole
radiates only 4 percent less than a resonant dipole, the only reason for
having
any longer length than infinitesimally short is to make it resonant?

Now that makes radiation efficiency per unit length hard to calculate, but
it does provoke thought regarding antenna designs
based on wavelength dimensions. Input impedance on a parallel circuit based
radiators gathers momentum in importance.
Art




So what do
you think the relation between voltage and current is in the short dipole?
Does
that bring to mind whether the max radiation occurs at the max voltage or
max
current portion of the dipole?

Walt, W2DU

On Thu, 11 Mar 2004 00:33:07 GMT, "aunwin"
wrote:

Input impedance on a parallel circuit based
radiators gathers momentum in importance.

Hi Art,

Only if 0.02% to 5% is all you need. Such is the legacy of eh designs
in comparison to full size antennas: more than 30dB down (0.1%
efficient if one is to be generous).

73's
Richard Clark, KB7QHC

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

Jim, AC6XG wrote:
"The amount of radiation emanating from any point woulf be proportional
to the rate at which energy traverses that point."

Amperes are the measure of current flow.

Best regards, Richard Harrison, KB5WZI

Walt, W2DU wrote:
"Have you guys ever considered that since the infinitesimally short
dipole radiates only 4 percent less than a resonant dipole, the only
reason for having any longer length than the infinitesimally short is to
make it resonant."

I`ll assume Walt`s infinitesimally short dipole is the same as Terman`s
elemental dipole. If so, I`ll quibble over the 4% . Terman`s table 23-1
on page 871 of his 1955 edition gives the directive gain of the
elementary doublet as 1.5 over the isotropic. The resonant dipole has a
1.64 gain . The difference is 0.14 or about 10% more from the 1/2-wave
dipole. Still no big deal.

Current is in the same direction in both halves of the elementalary
dipole no matter how short it is. Opposite charge polarities occupy
both elements and their effects tend to cancel on charges equidistant
from the middle of the antenna.

The field radiated in any direction is the vector sum of fields radiated
from infinitesimal elements, and field strength is proportional to
current.

Directional gain ignores losses. That`s the rub with the tiny antenna of
high capacitive reactance (the capacitance is small) and low radiation
resistance. The gain ratios are only valid with equal powers in
comparison antenna and subject antenna. To get the large current
required in the infinitesimal antenna to radiate the same power as the
1/2-wave dipole would be extremely difficult without enormous loss in
the match and load circuits.

Best regards, Richard Harrison, KB5WZI