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Scott wrote:
If you don't mind having a little less gain than is ultimately possible by using an antenna modeling program, the NBS (Nation Bureau of Standards) designs are pretty straight-forward. For a 6 element Yagi, here is element lengths and spacings for building with insulated elements (insulated from the boom, so I would use wood, 1" X 2" X 8.5') Lengths: Reflector = 3' 4" Driven = 3' 2-3/16" Dir 1 = 3' 7/8" Dir 2 = 3' 7/16" Dir 3 = 3' 7/16" Dir 4 = 3' 7/8" Spacing: Ref to Driven = (187.2/Fc) X 12 Spacing between all other elements = (234/Fc) X 12 where Fc is the design center frequency in MHz, ie 146 for the center of the FM portion). The spacing calculations give the answer in inches. Then you need to feed it. I use delta matches. Are you good at qrz.com? If so I can send you a drawing of the feed to get you started (but you would need an SWR meter that works at 2M to get it adjusted). Scott N0EDV Sorry, I didn't give an alternatives in my previous email. Please see the K1FO series in the ARRL antenna books. They are among absolutely the best possible, very replicable,, low build sensitivity, and fairly short to very long boom plans are available. If you do not have one of the ARRL Antenna books available, I, or others here, have copies as needed. tom K0TAR |
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