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art wrote:
. . . Any cursury look at a three D radiation pattern will immediately see that the main lobe is less than 50 % of the total radiation pattern . . . Out of curiosity, did you a) not read b) not understand, or c) not believe what I posted about the fraction of power in a Yagi's minor lobes? A cursory look at a 3D pattern is probably one of the least reliable ways to determine anything quantitative about an antenna pattern. By choosing the scale (e.g., field strength, power density, linear dB, ARRL-scale dB), you can make the relative sizes of the lobes just about anything you'd like and lead the casual observer to the conclusion of your choice(*). But why bother trying to divine a value from a 3D pattern, when it's so simple to numerically show that the power in the lobes is insignificant? (*) One of the slides in the "Antenna Basics" talk I've given at many hamfests shows several very different directional patterns, and I ask the audience which one is the most desirable. After the votes are in, I reveal that they're all the same antenna, just drawn to different common and legitimate scales. Roy Lewallen, W7EL |
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