What you're probably seeing is a numerical problem in the NEC calculating
engine. It's very fussy about the region near a source, and doesn't like small
loops which include a source. You should run an Average Gain check (see
"Average Gain" in the EZNEC manual index), which will reveal whether this is
the problem.

The double precision calculating engine in EZNEC+ is considerably more
tolerant of small loops, but can still have problems with average gain for
other reasons.

Roy Lewallen, W7EL

Hi Roy,

thanks for the tip.

As a matter of fact without the hairpin the average gain is almost zero, whilst
with the hairpin is about -0.8 dB, that correponds to the gain drop I notice. So
the problem you had anticipated actually occurs.

I then tried to simulate the hairpin with a proper-length shorted trasmission
line and, doing so, the average gain is almost 0. Evidently the program does not
like the short hairpin loop.

73

Tony I0JX