Does it matter that the outer sleeve and radiator element are connected
together in the model ?

The actual antenna only connects the sleeves to earth braid and the
centre conductor does not touch anything ?


Frank wrote:
----------o---------- ----------
dipole extension

Do you think it makes sense? It is the only way I could think of modeling
it with NEC.

Hi Frank,

No. The extension lies in the null of the dipole. As such, it would
be no mystery that it has so little influence.

To model it correctly requires some form of cage or skirt of wires as
Wes has provided in this thread.

73's
Richard Clark, KB7QHC


I did not notice that somebody had attempted what you suggest. I translated
the coordinates into regular NEC2, and it does run. It appears to violate
some NEC2 criteria, but not sure how critical the model is. Obviously I
cannot use the "Minninec" ground, so have substituted an average S/M ground
with the coax end about an inch above the ground. I had assumed the antenna
was for HF, so it is probably impractically high, causing multiple lobing.
A free space model might provide more meaningful results.

73,

Frank

On Tue, 11 Oct 2005 03:20:51 GMT, David wrote:

Does it matter that the outer sleeve and radiator element are connected
together in the model ?

Hi David,

ALL connections contribute to radiation. Their combination is what
builds the familiar lobe characteristic.

The actual antenna only connects the sleeves to earth braid and the
centre conductor does not touch anything ?

That's one way, the convention - could be t'other way 'round too; and
perhaps more interesting.

73's
Richard Clark, KB7QHC

On Tue, 11 Oct 2005 03:20:51 GMT, David wrote:

Does it matter that the outer sleeve and radiator element are connected
together in the model ?

The actual antenna only connects the sleeves to earth braid and the
centre conductor does not touch anything ?

In the model I supplied, the first wire (cleverly labeled "Source
Wire") contains the source. By modeling convention, a source must be
"on" a wire, so the wire connecting the upper radiator to the
skirt/sleeve is equivalent to the transmitter (coax center conductor)
and is *not* a short circuit.