"Art Unwin" wrote
The antenna compendium states that an assumption
is made with MoM programs that an assumption is made that current
in a radiator is sinusoidal where as we all know that the current
degrades in aplitude dependent on radiator length.
_____________

Art, the current distribution along even the shortest (fractional
wavelength), constant OD radiator also is ~sinusoidal.

Currrent always is near zero at the open end of a linear radiator of every
physical length. The shape of the current wave formed along a very short
radiator appears to be very close to triangular. But in fact that
"triangular" current distribution is just a very short section of a
sinusoidal waveform.

N.B. that MoM programs show exactly this for radiators that are very short
in terms of electrical wavelengths. This also is proven mathematically in
the antenna engineering textbooks of Kraus, Balanis, Johnson & Jasik, etc
etc.

RF

** Posted from http://www.teranews.com **

RE my earlier post starting:
Art, the current distribution along even the shortest (fractional
wavelength), constant OD radiator also is ~sinusoidal. etc

** Posted from http://www.teranews.com**

That was my first (and last) use of Teranews, who took a couple of
days to post it. I had given up on them, and switched to Google to
make the post. Now this duplicate shows up - sorry.

richard Fry wrote:
"Art, the current distribution along even the shortest (fractional
wavelength), constant OD radiator also is sinusoidal, etc."

Yes. One of the first things Maxwell noted of his equations is that they
have the form of equations desceibing wave movements in water.

One of my (new to me) books on electromagnetics supports Art`s use of
Gauss.
Stanley V. Marshall in "Electromagnetic Concepts & Applications" says:
"In most cases, it is much easier to evaluate the scalar field direction
from which we can evaluate the electric field intensity than to find the
electric field intensity directly. In cases of symmetrical charge
distribution, using Gauss`s law to find the electric field intensity is
still the simplest method, if we can find a Gaussian surface that will
allow us to remove the field function from under the integral sign.

There are several ways to solve the same problem. Even if we use
photons, all must give the same answer.

I appologize for disparaging Art`s methods.

Best regards, Richard Harrison, KB5WZI

On Jan 14, 12:08*pm, (Richard Harrison)
wrote:
richard Fry wrote:

"Art, the current distribution along even the shortest (fractional
wavelength), constant OD radiator also is sinusoidal, etc."

Yes. One of the first things Maxwell noted of his equations is that they
have the form of equations desceibing wave movements in water.

One of my (new to me) books on electromagnetics supports Art`s use of
Gauss.
Stanley V. Marshall in "Electromagnetic Concepts & Applications" says:
"In most cases, it is much easier to evaluate the scalar field direction
from which we can evaluate the electric field intensity than to find the
electric field intensity directly. In cases of symmetrical charge
distribution, using Gauss`s law to find the electric field intensity is
still the simplest method, if we can find a Gaussian surface that will
allow us to remove the field function from under the integral sign.

There are several ways to solve the same problem. Even if we use
photons, all must give the same answer.

I appologize for disparaging Art`s methods.

Best regards, Richard Harrison, KB5WZI

Accepted.
Does the book extend the rule of equi;ibrium to helical antennas by
applying cancellation
of the lumped loads provided by this means of construction, which thus
provides the means for smaller antennas?
Regards
Art Unwin KB9MZ.....xg (uk)

Richard Fry wrote:
But in fact that
"triangular" current distribution is just a very short section of a
sinusoidal waveform.

Yes, for a few degrees around the zero crossing
point, y=Ax+B can be a close approximation.
--
73, Cecil http://www.w5dxp.com