NEC-LIST: Which excitation should I use ?

Hi

I have been modelling broadcast antennas for a number of years and have
recently upgraded to NEC4. I have run into a small problem modelling arrays
and would appreciate some guidance.

Modelling cluster of two or three quarter wave monopoles using an EX 0
command with NEC2 gave an obviously incorrect radiation pattern, so I
inserted an NT command, which I think converts EX 0 to a current feed.
This seemed to produce the expected radiation pattern.

I would be pleased if anyone could explain why I have to do this, and
provide some criteria to decide which form of excitation I should use, when
using NEC4..

Phil Ede

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