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On the Effects of Driven Element L/D Ratio and Length in VHF-SHF Yagi-Uda Arrays

Wireless engineering and Technology 2023年第1期14卷 1-25页

作者： Richard A. Formato consulting engineer & registered patent attorney of Counsel Emeritus Cataldo & Fisher LLC Harwich MA USA

While the Yagi-Uda array has been studied for decades, one issue appears to have received less attention than perhaps it should, namely, the effects on performance of the array’s driven element length and its length-to-diameter ratio. This paper looks at that question. It shows that decreasing the L/D ratio increases impedance bandwidth, but it may shift the IBW band sufficiently far from the design frequency that other parameters such as gain and front-to-back ratio probably are adversely affected. It also shows that array performance is not relatively independent of element diameters. This paper also investigates the effect of lengthening the driven element, which can substantially improve IBW. Several iterations of a 3-element prototype and improved arrays are modeled with the Method of Moments and discussed in detail. A five step design procedure is recommended and applied to a Genetic Algorithm-optimized 3-element Yagi at 146 MHz. This array exhibits excellent performance in terms of gain, front-to-back ratio, and especially impedance bandwidth (nearly 14% for voltage standing wave ratio ≤ 2:1 with two frequencies at which 50 ? is almost perfectly matched). While the analysis and recommended design steps are applied to cylindrical array elements, which commonly are aluminum tubing for stand-alone VHF-SHF Yagis, they can be applied to other element geometries as well using equivalent cylindrical radii, for example, Printed Circuit Board traces for planar arrays. One consequence of lengthening the driven element while reducing its L/D ratio is that some reactance is introduced at the array feedpoint which must be tuned out, and two approaches for doing so are suggested.

关键词： Yagi Array Driven Element Impedance Bandwidth

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Central Force Optimization with Gravity <0, Elitism, and Dynamic Threshold Optimization: An Antenna Application, 6-Element Yagi-Uda Arrays

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Wireless engineering and Technology 2021年第4期12卷 53-82页

作者： Richard A. Formato consulting engineer & registered patent attorney of Counsel Emeritus Cataldo & Fisher LLC Woburn MA USA

This paper investigates the effect of adding three extensions to Central Force Optimization when it is used as the Global Search and Optimization method for the design and optimization of 6-elementYagi-Uda arrays. Those extensions are Negative Gravity, Elitism, and Dynamic Threshold Optimization. The basic CFO heuristic does not include any of these, but adding them substantially improves the algorithm’s performance. This paper extends the work reported in a previous paper that considered only negative gravity and which showed a significant performance improvement over a range of optimized arrays. Still better results are obtained by adding to the mix Elitism and DTO. An overall improvement in best fitness of 19.16% is achieved by doing so. While the work reported here was limited to the design/optimization of 6- element Yagis, the reasonable inference based on these data is that any antenna design/optimization problem, indeed any Global Search and Optimiza

关键词： Yagi Yagi-Uda Array Antenna Antenna Design Optimization Central Force Central Force Optimization CFO CFO-GED Negative Gravity Elitism Dynamic Threshold Optimization DTO Dynamic Threshold Metaheuristic Evolutionary Computation

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Climate Change Science &Propaganda

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International Journal of Geosciences 2015年第12期6卷 1323-1338页

作者： Michael D. Nelson Retired Chemical engineer and patent attorney Pleasanton CA USA

This article addresses the relationship between science and propaganda using the Climate Change controversy as a study model. The United Nations International Panel on Climate Change (IPCC) is the recognized leader on this model issuing multiple Assessment Reports. This review begins with a discussion of the basics—what is propaganda and how does it work, followed by whether the IPCC adopted or rejected it. Next explored is how propaganda can be seamlessly fused into “report writing” in a way that arouses and makes interesting humdrum details. Some unexpected results emerged from current and historical observation data involving the Greenhouse theory, CO2 sources, ocean pH, sea levels, and ice balances. The final section confronts whether “a point of view” constrains objectivity in favor of outcome. The overall conclusion is that the earth is boringly healthy.

关键词： Climate Change IPCC Propaganda Greenhouse Theory Ozone Ocean pH Sea Level Ice Balance

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Oceans, Ice &Snow and CO₂ Rise, Swing and Seasonal Fluctuation

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International Journal of Geosciences 2016年第10期7卷 1232-1282页

作者： Michael D. Nelson David B. Nelson Retired Chemical engineer and patent attorney Pleasanton USA Biology & Environmental Science Granite Bay USA

Carbon dioxide rise, swing and spread (seasonal fluctuations) are addressed in this study. Actual CO2 concentrations were used rather than dry values. The dry values are artificially higher because water vapor must be removed in order for the NDIR instrument to work and is not factored back into the reported numbers. Articles addressing these observations express opinions that are divergent and often conflicting. This investigation resolves many of those inconsistencies. The data were obtained from many measuring stations at various latitudes since 1972 and then graphical compared to changes in sea temperatures, fossil fuel emissions, humidity, and seasonal ice and snow changes. In analyzing the data, various parameters were addressed including: variability, R squared curve values, correlations between curves, residence times, absorption percentages, and Troposphere effects. Mass balance calculations were also made to corroborate viability. The CO2 “rise” over a 33-year period from a slight ocean temperature increase (0.7°F) contributed 2.3 percent of the total rise while fossil fuel emissions contributed 1.5 percent. The overwhelming majority (60 ppmv, 96%+) was caused by other factors including ocean and land biology as well potential errors in fundamental hypotheses. With respect to “spread” (seasonal CO2 fluctuations) at the Polar Circles, graphical analysis with high correlations supported by mass balance calculations confirm that ice and snow are the primary cause and explain why the concentrations are the highest at these cold locations. The global variations in “swing” remain uncertain.

关键词： CO2 Rise Seasonal Fluctuation Ice & Snow Fossil Fuel Emissions Biology

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