"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