I can understand your confusion and doubt. I hope this says it in
clear terms:

In the revised model with the hairpin done as three wires, the
original D.E. single wire was replaced by three wires: a 10cm long
center section which should have the source in its center, and a
"left" and a "right" outer section. Those three sections are three
separate wires. The reason to break the original single wire into
three wires is so that there will be wire "ends" to connect the
hairpin wires to. You can only connect wires at their ends, even
though they have multiple segments. So yes, in the new model the
source is just in the middle of the wire which is the middle section
of the D.E.

Thanks for your clarification that confirms my expectation that I shall put the
generator in the middle of the 10 cm-long center section of the D.E..

Everything works fine and, for a reference 200-ohm resistance, I get an SWR of
almost 1 not too far away from the frequency at which it actually occurs.

If I may take a bit more of your time, I have noted two inconsistencies:

- with the hairpin EZNEC gives an antenna gain of 12.76 dB but, if I just delete
the three hairpin segments leaving everything else unchanged, the gain grows up
to 13.59 dB. I am surprised about that result, as I had understood that, in
EZNEC, the antenna gain has nothing to do with the way the antenna is fed.

- with the hairpin, at the antenna resonant frequency EZNEC shows an impedance
of 200.5 +j2.1 ohm which obviously corresponds to an SWR of almost 1. If I
remove the hairpin, at the same frequency EZNEC shows an impedance of 42.4 - 39
ohm which could seem reasonable, but it is actually not. As a matter of fact, by
applying the appropriate series-to-parallel conversion formula, that impedance
corresponds to the parallel of a 78.2 ohm resistance and a 85.1 ohm capacitive
reactance. Resonating the reactive capacitance with an equal (though opposite)
reactance hairpin, the remaining resistance would be just 78.2 ohm, that is far
away from the 200 ohm EZNEC shows with the hairpin installed.

May I have your opinion?

73

Tony I0JX