On Apr 9, 9:02 am, "Antonio Vernucci" wrote:
Tom and Wim,

I agree with your concluion that the bandwidth narrowness is due to the antenna
design and not to the matching system.

I have simulated the antenna on EZNEC and the narrow band property of the
antenna is very evident.

I would like to also put the hairpin in the EZNEC model, but I am not very good
at EZNEC and I would not now know to do it.

If you are interested I can send you the EZNEC file via e-mail.

73

Tony I0JX

Hi Tony,

I would be happy to have a look at the file and add the hairpin if you
wish. But I can also guide you through doing it yourself. It should
be quite easy. Simply click on the " Trans Lines" button, the second
one below Sources in the main window. Specify the first end the
same as the source--perhaps 50% along wire 2, assuming the D.E. is
wire 2. That end will then be in parallel with the source. You can
type "S" in for the other end's wire #, or if you click in the End 2
Wire # box, you should see a list of "open" and "short" and you can
select "short" there. Then enter the length, Z0, velocity factor (1)
and loss. Reverse or normal doesn't matter since only one end is
connected.

In as much as the hairpin actually IS in the field of the antenna, and
couples to it to some degree, there may be a small error in using the
EZNEC transmission line, instead of entering it as wires, but for a
short stub I would not expect that to be a significant issue. I do
know that the 1/4 wave stub used to separate elements of a collinear
does couple to the antenna fields and that coupling is a significant
factor in the performance of the antenna--or at least that is what
R.W.P. King tells us.

And...thanks much for the interesting discussion topic. I learned a
few things from it.

Cheers,
Tom