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Art Unwin wrote:
"But my main question still remains a pointer to a technical article that discusses the possibility or impossibility of what I have stated." I don`t get the question, but it seems to me, Art wants to know if anyone has written of a method to make maximum gain correspond with maximum front-to-back ratio in a Yagi. I haven`t seen it. There is a third factor in the compromise, 50-ohm feedpoint (or some other convenient impedance). Kraus gives the Yagi-Uda story in "Antennas" There has been much experimentation and the tradeoffs still exist. Don`t close the patent office yet. Almost everything can be improved. Art may be implying that he thinks he has a way to make a better Yagi. I hope so. The "ARRL Antenna Book" is a good place to see where the art was at the time of publication. The Antenna Book devotes a chapter to the Yagi, No. 11 in my 19th edition. The directional patterns show a pair of troublesome sidelobes in addition to the mainlobe. It`s the sidelobes which are suppressed at the sacrifice of a little gain. Parasitic arrays are close-spaced for significant excitation. Close-spacing means close-coupling which lowers the drivepoint impedance. It`s a tradeoff again because low impedance eventually limits the antenna`s efficiency. Best regards, Richard Harrison, KB5WZI |