Long-Boom Yagi Studies
L.B. Cebik, W4RNL

~ 488 Pages plus 360 Modeling Files in EZNEC~

ost generalizations about long-boom Yagis have emerged from too few samples covering even fewer basic designs.  To rectify the situation partially, L. B. Cebik has systematically modeled in NEC-4 seven complete Yagi series with boomlengths extending from 2 l up to 11 l or 14 l , depending on the series limits.  He has collected and sorted data from well over 2500 model runs to produce the compendium of information within the covers of Long-Boom Yagi Studies.

After a brief introduction and a sampling of designs for the 70-cm amateur band, Cebik begins a detailed survey of performance patterns and trends for a number of classic and experimental Yagis designs at all lengths up to either the series limit or 14 l , whichever comes sooner.  The descriptive analysis includes the famous DL6WU series and a more recent series from VK3AUU, as well as other "trimming-Yagi" series.  N6BV contributed a sequence of individually optimized Yagis to the study.  The result is a clearer understanding of which performance characteristics belong to particular designs and which are more general properties of long-boom Yagis, including the role of element density in the performance patterns.

 The study includes a detailed modeling analysis of vertical 2-stacks optimized for maximum gain, with some results not predicted by standard means of estimating optimum stacking separations.  The volume takes up the question of optimizing sidelobe performance with a provisional compressed-spacing design that, above 11 l of boom, reduces sidelobe strength in both E- and H-planes by 10 dB relative to classical designs.  Applying the results to vertical 2-stacks shows that the stack spacing for optimal sidelobe performance may be a partial function of an array's single-unit sidelobe performance.  The study closes with a comparison of some long-boom Yagi rules of thumb with modeling results.

W4RNL's study consists of 3 major parts.  There are 270 large-format pages of highly illustrated text.  Appended to the text are 6 appendices (212 pages) containing frequency sweep graphs for each sampled length of most of the long-boom Yagi series surveyed.  The purpose of these appendices is to permit the reader to develop his or her own analyses of the long-boom Yagi data.  To allow for further study, the volume also contains 360 EZNEC-format models for the antennas included in the study.

Cebik's volume restricts itself to descriptive analyses of the patterns and trends in long-boom Yagi performance.  NEC-4 modeling may not capture all of the loss factors associated with range studies.  However, it provides a means of developing a large and useful quantity of data that permits direct comparisons among Yagi designs.  Long-Boom Yagi Studies provides a compendium of both raw and distilled data that may interest anyone who uses VHF and UHF high-performance Yagi-Uda antennas.

Considered an expert on antennas, L. B. has published over a dozen books, with works on antennas for both the beginner and the advanced student. Among his books are a basic tutorial in the use of NEC antenna modeling software and compilations of his many shorter pieces. His articles have appeared in virtually every amateur radio publication, with translations of some into several languages. Retired Professor from the University of Tennessee at Knoxville, LB is Technical & Educational Advisor to the ARRL and Technical Editor for antenneX.

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