Practical_Antenna_Handbook_0071639586

314 P a r t I V : D i r e c t i o n a l H i g h - F r e q u e n c y A n t e n n a A r r a y s
ences. However, there are many excellent resources already in print, as summarized
here. Perhaps more to the point, however, the easy availability of inexpensive or free
antenna modeling software makes it possible for any reader interested in designing and
building a custom Yagi from scratch to “play with the numbers” and develop his/her
own intuitions as to how key parameters (forward gain, F/B ratio, bandwidth, etc.)
vary as dimensions are changed.
Further Reading
The designs and construction techniques of this chapter do not take into account the
special demands of severe environments. The unusually high winds of mountaintops
and coastal areas, the icing that must always be expected between midlatitudes and the
poles, and saltwater mist for coastal and island installations all impose extra burdens
on antennas and their supports. Further, the interplay between mechanical and electrical
considerations becomes far more critical the longer the boom and elements are.
The definitive resource for understanding why and how to strengthen a Yagi is
Physical Design of Yagi Antennas, by David B. Leeson, W6NL (ex-W6QHS), available
from ARRL. In addition to explaining why and to what extent booms, elements, brackets,
and masts should be reinforced and balanced, it is chock-full of valuable practical
information—extending beyond purely mechanical considerations—for anyone interested
in modifying commercial antennas or designing and building his/her own.
Another seminal work is Yagi Antenna Design, by James L. Lawson (deceased), ex-
W2PV, ARRL, 1986. Here the principal focus is on the electrical design and performance
of HF Yagis, and many practical families of designs with complete dimensions are provided
for beams having between two and eight elements. Unfortunately, this book predates
amateur access (in the United States, at least) to the so-called WARC bands at 30,
17, and 12 m.
Low-Band DXing, by John Devoldere, ON4UN, ARRL, fifth edition, 2011, is not primarily
about Yagi antennas but does treat their design and performance on 80 and 40 m
at some length. There is also an extended section on hairpin matching, including some
explanatory calculations coupled with experimental techniques for obtaining the best
match.