    AN-SOF ANTENNA SIMULATOR
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The Extended Double Zepp (EDZ) is a center-fed dipole antenna that is approximately 1 1/4 wavelengths long and is horizontally installed. Dipoles larger than a wavelength have always garnered attention due to their higher gain compared to a half-wave dipole. However, they come with the drawback of a very high capacitive reactance at the antenna terminals, which complicates matching to the commonly used 50 Ohm coaxial line in the radio ham operator community. This is in contrast to a resonant dipole, which is typically near half the wavelength in length.

In cases where a directional radiation pattern is required, a phased array consisting of two identical EDZ dipoles can be utilized, as demonstrated in this example model. The array operates at a frequency of 28.5 MHz (10 m band) and the dipoles are separated by approximately 1/4 of a wavelength. The feed point is situated at the center of the driven dipole, while the other dipole acts as a parasitic element. It is fed by a 600 Ohm two-wire transmission line, which is implicitly incorporated into the model. Additionally, each dipole is loaded with two capacitors symmetrically placed on either side of the feed point. This configuration transforms the two capacitively loaded phased dipoles into a directional antenna with a favorable input impedance.

When this array is positioned at a height equivalent to one wavelength above an average real ground plane, the radiation pattern exhibits a tilt of approximately 12 degrees above the horizon, with a secondary lobe becoming visible. Despite this, the array achieves a respectable gain of 14 dBi and an input impedance of 59 + j106 Ohm. This value is more manageable for matching to a 50 Ohm coaxial line. In comparison to a Yagi-Uda antenna with the same gain, this phased array offers a cost reduction in terms of wiring.

