Eddie
what i have read from more multiple sources when people ask about coax dipoles using the transmissionline fuction to model coax to include coax losses it treats it as a 2 wire transmissionline with no outside surface of the braid to carry current & radiate unless you add a 3rd wire,
the vector is a coaxial arrangement but its not created using the tl function,
its wires close spaced at an accute angle & theres a few ways it can radiate which i have talked about before,
you don't need any extra wires to simulate the outside of the cone if you are not using the tl function to simulate coax cable that radiates unless you are modeling coax that radiates,
if you terminate the vector cone with a resistive load all you will see is some small radiation due to the wires not been parallel like any tapered line terminated with a resistor, which is what Henry's model shows,
in the vector the cone is not terminated with a reistive load its unbalanced and must radiate more than the radiation due to none parallel wires however large or small that is,
heres what the eznec manual tells us about coax
"A non-radiating coaxial cable is electrically identical to a non-radiating two-wire line, so an ordinary transmission line model can be used for modeling a non-radiating coaxial line.
A radiating coaxial cable can be modeled quite well with a combination of transmission line model and a wire.
The transmission line model represents the inside of the coax, and the wire represents the outside of the shield.
The wire is the diameter of the shield, and connected where the shield of the actual cable is.
It should follow the same physical path as the real coaxial cable.
One of the example files, DipTL.ez, shows how this is done. (See its Antenna Notes file for more information.)
If the coax cable doesn't radiate, the current on the additional wire will be zero, and the additional wire contributes nothing to the analysis so can be removed."
and about open wire feedlines
"There's no way to use the transmission line model to accurately model a radiating two-wire transmission line (one with common mode current present). If it's necessary to do this, the line will have to be modeled as two parallel wires. See Closely Spaced Wires for precautions"
"EZNEC transmission line objects don't interact with the antenna fields.
That is, the currents in the model's two conductors are always equal and opposite, so the line doesn't radiate or have current induced by coupling.
In many real-life cases, a transmission line does interact with the antenna fields, and becomes a radiating part of the antenna.
This can be caused by coupling to the antenna due to non-symmetrical placement of the feedline, or by presenting the feedline with an unbalanced source or load.
EZNEC transmission line objects are suitable for modeling symmetrically-placed balanced lines such as a log-periodic feed distribution line or W8JK phasing line.
They aren't suitable for modeling, for example, a quarter-wavelength phasing stub extending outward from a collinear antenna, since the stub wires in a real collinear antenna have unbalanced currents and will radiate.
Coaxial lines laid on the ground, such as in a vertical phased array feed system, may carry current on the outside just like a ground radial wire.
In many cases this can be ignored and the EZNEC Pro model used.
A coaxial cable with field interaction (that is, with current flowing on the outside of the shield) can be modeled with a combination of a wire and transmission line object as described in Modeling Coaxial Cable.
A two-wire line which interacts with the antenna's fields has to be modeled as wires.
