I don't know if others were as skeptical as I was about the broadband
20-meter yagi design presented in the 10/96 CQ. It just looked a little too
good to be true, particularly the very small reactances at the band edges,
combined with excellentgain and F/B.
Anyhow, just for fun, I converted the dimensions to an EZNEC wire table,
and, sure enough:
gain figures are as quoted across the band (note that these are dBi in free
space, and the antenna picks up over 5 dB from ground reflections when
modeled over average ground at 100 ft).
feedpoint data are close to, if not exactly the same as quoted
F/B is very consistent at the band edges, but plotting the pattern shows
that the sharp peak in F/B at 14.2 is due to a notch in the pattern at
exactly 180 degrees - the actual front-to-largest-minor-lobe at low angles
is more like 35 dB, and there are some high-angle minor lobes that are maybe
as little as 25 dB down, but they're narrow.
Both gain and F/B are superior to the 5-element reference yagi provided with
EZNEC, and the feed-point behavior is MUCH better from band-edge to band-edge.
But here's my question - how does the W6NGZ antenna compare to the best
5-element monobanders out there - W2PV and N2FB designs, or the Hygains (is
there a 205CA?)? Has he really got something better here, particularly in
terms of SWR bandwidth?
73, Pete Smith N4ZR
n4zr@contesting.com
... and not changing!
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