ANTENTOP- 01- 2009, # 011

Compact Cage Antenna

Vladislav Shcherbakov, RU3ARJ, ru3arj@mail.ru

Credit Line: www.cqham.ru

Everyone knows "classical" quad antenna. Its perimeter is equal to wavelength. Each side of the quad is 1/4 wavelength.

Amplification of the "classical" quad antenna is 3-dBi, input impedance (in a free space) is close to 120-Ohm (Figure 1). Good antenna but the size!

Figure 1. "Classical" quad antenna

It is possible to reduce its size by folding it in a "cage"shape. The simplest cage in which the antenna may be transformed is a cage of 10 sections 0.11 wavelength each. The Compact Cage Antenna (CCA) gain is 1.5-dBi and input impedance is close to 50-Ohm. Figure 2 shows the CCA grabbed from MMANA. There are shown antenna currents and the source. MMANA file for the antenna (named Trihat- quad) may be found at MMANA "Antenna Library" (References 1) or loaded by the link below.

Figure 3 shows free space radiation patterns for Compact Cage Antenna, Figure 4 shows Compact Cage Antenna radiation patterns at 1/3 wavelength height above the ground, Figure 5 shows Compact Cage Antenna radiation patterns at 1.0 wavelength height above the ground.

Compact Cage Antenna may be fed at the low corner with the twin line (see Figure 6). The antenna may be fed with coaxial cable through a balun as well.

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