Page:Electronics Technician - Volume 7 - Antennas and Wave Propagation - NAVEDTRA 14092.pdf/43

 Figure 2-36.-Seven—foot shf SATCOM antenna.

Figure 2-37.—Four-foot shf SATCOM antenna.

MATCHING NETWORKS

An antenna matching network consists of one or more parts (such as coils, capacitors, and lengths of transmission line) connected in series or parallel with the transmission line to reduce the standing wave ratio on the line. Matching networks are usually adjusted when they are installed and require no further adjustment for proper operation. Figure 2-38 shows a matching network outside of the antenna feedbox, with a sample matching network schematic.

Matching networks can also be built with variable components so they can be used for impedance matching over a range of frequencies. These networks are called antenna tuners.

Antenna tuners are usually adjusted automatically or manually each time the operating frequency is changed. Standard tuners are made with integral enclosures. Installation consists simply of mounting