144-146 13 Elements Antenna

by UA9OFC

The FM-modulation is widely adopted in wave band 145-146 MHz with vertical irradiation polarized. But necessity of long-distance QSO execution in SSB and CW modes in corresponding frequency range (144-145 MHz) requires to use the coupled directional antennas with different polarization kinds. It results in design inconveniences, increasing materials output ratio and cost of antennas system.

Adjusted antenna, constructively include two mutually orthogonal antennas (with vertical and horizontal polarization), which locate on one boom. For horizontal and vertical antenna's parts resonance frequencies are setup in the beginning (144-145 MHz) and in the end (145-146 MHz) of range, accordingly.

The given antenna, also differs from traditional Yagy-antennas, by that has variable length of the directors towards the end of the boom. In practice it promotes reduction level of side lobes in the polar pattern.

The switching between horizontal and vertical feed elements (vibrators) implement through the coaxial relay, located in immediate proximity from vibrators. It allows to feed the antenna by single 50 ohm fider.

The gamma matching system used for a feed both vibrators by 50-ohm cable (see fig 1,2).

The characteristics and parameters of the antenna are shown below.

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