Does anyone know how I can model a coaxial sleeve antenna
on EZNEC ?

I know how to enter a standard Vertical 1/2 wave but not sure how
to represent the coax going up through the tubing(sleeve) in the lower
portion.

Thanks in advance.

In my humble opinion, EZNEC is a POS for anything other than a simple "wire
antenna". Try to do a true ground plane with bent radials? Try to do a
simple patch? Try to do a J? Try to do ANY configuration other than a wire
dipole and the sucker chokes.

Jim



"David" wrote in message
...
Does anyone know how I can model a coaxial sleeve antenna
on EZNEC ?

Jim,

What would be your alternate suggestion ?

Thanks

Regards

David

ERST Engineering wrote:
In my humble opinion, EZNEC is a POS for anything other than a simple "wire
antenna". Try to do a true ground plane with bent radials? Try to do a
simple patch? Try to do a J? Try to do ANY configuration other than a wire
dipole and the sucker chokes.

Jim



"David" wrote in message
...

Does anyone know how I can model a coaxial sleeve antenna
on EZNEC ?

On Fri, 7 Oct 2005 20:38:43 -0700, "RST Engineering"
wrote:

In my humble opinion, EZNEC is a POS for anything other than a simple "wire
antenna". Try to do a true ground plane with bent radials? Try to do a
simple patch? Try to do a J? Try to do ANY configuration other than a wire
dipole and the sucker chokes.

I suggest that it is your models that may be choking. EZNEC uses the
NEC engine for caculations and NEC can do all the items you mention
above.

Danny, K6MHE

email: k6mheatarrldotnet
http://users.adelphia.net/~k6mhe/

"David" wrote in message
...
Does anyone know how I can model a coaxial sleeve antenna
on EZNEC ?

I know how to enter a standard Vertical 1/2 wave but not sure how
to represent the coax going up through the tubing(sleeve) in the lower
portion.

Thanks in advance.

Just model a vertical dipole. The presence of a coaxial cable, within the
lower conductor, will not effect its performance. For your model both upper
and lower conductors should be the same diameter. Dissimilar diameters in a
model can produce erroneous results.

NEC has its limitations, but alternative, FEM based, programs can cost tens
of thousands of dollars.

Regards,

Frank

On Sat, 08 Oct 2005 13:36:37 GMT, "Frank"
wrote:

"David" wrote in message
...
Does anyone know how I can model a coaxial sleeve antenna
on EZNEC ?

I know how to enter a standard Vertical 1/2 wave but not sure how
to represent the coax going up through the tubing(sleeve) in the lower
portion.

Thanks in advance.

Just model a vertical dipole. The presence of a coaxial cable, within the
lower conductor, will not effect its performance.

But the presence of the coax below the antenna sure will.

RST Engineering wrote:
In my humble opinion, EZNEC is a POS for anything other than a simple "wire
antenna". Try to do a true ground plane with bent radials? Try to do a
simple patch? Try to do a J? Try to do ANY configuration other than a wire
dipole and the sucker chokes.

I've modeled ground planes with bent radials and J antennas
using EZNEC and got reasonable results. Never tried a patch.
EZNEC's limitations are well known and well documented so
knowledgeable users can avoid those pitfalls. Of course,
nothing is foolproof.
--
73, Cecil http://www.qsl.net/w5dxp

Just model a vertical dipole. The presence of a coaxial cable, within the
lower conductor, will not effect its performance.

But the presence of the coax below the antenna sure will.

As an experiment I modeled a #14 AWG, 133 segment,134 ft free space dipole.
The input impedance at 3.575 MHz is 74.01 - j 0.749 ohms. Adding an
additional 25 ft wire at one end -- ends separated by 1.2" -- the input
impedance becomes 74.155 - j1.97 ohms. There is no discernable effect on
the radiation pattern.

While this test is not precisely equivalent; the presence of a, non
connected, axial extension appears to have only a minimal effect on the
antenna parameters.

Regards,

Frank

On Sat, 08 Oct 2005 16:31:17 GMT, "Frank"
wrote:

While this test is not precisely equivalent; the presence of a, non
connected, axial extension appears to have only a minimal effect on the
antenna parameters.

Hi Frank,

And did resonance go unperturbed?

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Sat, 08 Oct 2005 16:31:17 GMT, "Frank"
wrote:

While this test is not precisely equivalent; the presence of a, non
connected, axial extension appears to have only a minimal effect on the
antenna parameters.

Hi Frank,

And did resonance go unperturbed?

73's
Richard Clark, KB7QHC

Hi Richard,

A nominal 2.5 kHz shift, at 3.575 MHz (0.07%), is about all I can detect.

73,

Frank