Howdy gents,

I thought that the problem of the hairpin or Beta Match was kicked around
way back, please see http://www.k3bu.us/beta_match.htm

Hairpin is shortening the (most important) radiating part of the driven
element where the current is the highest.
The best way to match the long antennas with low feedpoint at the driven
element is to use the folded dipole or Quad element, as I used in my Razor
Beams http://www.k3bu.us/razor_beams.htm

First you shorten the driven element, reduce the effective length, then you
apply lossy matching and then you see less gain and narrower bandwidth.
Folded dipole or quad elements fix that.

Yuri, K3BU.us



"Antonio Vernucci" wrote in message
...
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