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Multi Wire Flat Top Antenna

Construction of a flat top antenna.

The Inverted L antenna depicted on another page on this site has a 25’ vertical section and a single wire, 50’ horizontal section. The value of the impedance at 1700 kHz is : Impedance = 2.25 - J 508.5 ohms

A modified version of this antenna uses a two wire 50' horizontal section or "flat top". The horizontal sections are 5' apart and are connected together at each end of the horizontal section. This approach has greater capacitance to ground, lowering the resonance of the antenna (although resonance is still above the BCB!) The impedance of this antenna at 1700 kHz is: Impedance = 2.608 - J 265.2 ohms

Notice also that the resistance part of the complex impedance is slightly greater. The plots for these two antennas are only marginally different. The real difference is in the reactive part of the impedance.

Reducing the spacing to 30" for the flat top elements still provides a smaller reactive component than the plain inverted L. For the 30" spacing: Impedance = 2.552 - J 300.8 ohms

Construction of a flat top antenna.

Elevation plot of the inverted L, 2 wire Flat Top with 5' spacing

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