On Tue,4/7/2015 1:06 PM, Joe Subich, W4TV wrote:
Worth noting when evaluating the N2IC report is that the C31XR has an
effective boom length of 25 feet on 20 meters, 22 feet on 15 meters,
and 25 feet on 10 meters. The C31XR compares favorably with, but lags
the N6BV "optimized" Hy-Gain antennas in the Antenna Book by .5 dB on
20, 1.2 dB on 15 and .6 to 1.2 dB on 10. Dean's design goals with the
Antenna Book examples were balanced gain and front to back with
acceptable SWR across the band. Those examples are not "maximum
gain" designs.
Yes. BUT -- few of us would be happy with a design that wasn't
reasonably well balanced, at least for forward gain over the band and
SWR bandwidth. The ARRL Antenna Book does a good job of showing that,
with graphs of gain, SWR, and F/B all plotted vs frequency for designs
optimized for each of those parameters and for a balance between all
three. For the few Yagis I've designed, I've tried to optimize for gain
and reasonable VSWR over the desired frequency range, sacrificing F/B if
needed.
In his very useful book, "Array of Light," N6BT also makes a point of
making designs reasonably insensitive to variables that are difficult to
control, like mounting height and close building tolerances.
73, Jim K9YC
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