Antenna Focal Devices for Parabolic Mirrors

The purpose and general nature of the receiving pattern are discussed. The results of calculations for the resistance and reactance of wide-angle cone antennas in free space are given. Several cone antennas in hemispherical enclosures have been measured and the impedance and phase-angle curves are shown. These results indicate that cylinders are more desirable than cones; therefore, two cylindrical antennas in hemispheres are tested. The results of investigation show that by making the antenna more slender and providing fine tips: (a) the radiation resistance is increased, (b) the rate of change of phase angle at resonance is increased, and (c) the resonant frequency is lowered.