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Brad wrote:
"What would be your recommendations?" Brad also wrote: "---but do have an area for a tall vertical antenna." There are often obstructions in an otherwise line-of-sight path. Antenna gain is usually not enough to overcome an obstructed path. Antenna height can overcome the obstruction. Flagpoles are usually acceptable where antennas are banned. In Terman`s 1955 edition of "Electronis and Radio Engineering" on page 902 are found "Flagpole Antennas". These are balanced vertical dipoles, transformed to a coax feed through the bottom of the dipole. If the flagpole is tall enough, you receive FM broadcasts. Q = f/BW means your dipoe needs a Q of less than 4.8 to span 88 MHz to 108 MHz. The antenna would center upon 97.5 MHz, the geometric mean or center of the band. Such a bandwidth is likely impractical. You can settle for less or center the response on the part of the band you would most use. Multiply the lowest frequency of high interest by the highest frequency of high interest and take the square root of the product to find the frequency the dipole should be cut for. The fatter the dipole is, the lower its Q will be, and the more even its frequency response will be. You can probably do quite well with uneven response in your antenna is high enough. Best regards, Richard Harrison, KB5WZI |
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