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Old September 29th 06, 04:00 AM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jun 2006
Posts: 1,374
Default Yagi efficiency

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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