Page:Electronics Technician - Volume 7 - Antennas and Wave Propagation - NAVEDTRA 14092.pdf/37

 Figure 2-25.—AS2802/SRC dicage antenna.

reason for the high installation is that vertical conductors, such as masts, rigging, and cables in the Vicinity, cause unwanted directivity in the radiation pattern.

For best results in the Vhf and uhf ranges, both transmitting and receiving antennas must have the same polarization. Vertically polarized antennas (primarily dipoles) are used for all ship-to-ship, ship-to-shore, and air-to-ground Vhf and uhf communications.

The following paragraphs describe the most common uhf/Vhf dipole antennas. All the examples are vertically-polarized, omnidirectional, broadband antennas.

Biconical Dipole

The biconical dipole antenna (fig. 2-26) is designed for use at a normal rf power rating of around 250 watts, with a vswr not greater than 2:1. All major components of the radiating and support structures are aluminum. The central feed section is protected and waterproofed by a laminated fiberglass cover.

Figure 2-26.—AS-2811/SRC Biconical dipole antenna. 2-15