The components that connect, interface, and otherwise transfer RF energy within a given system or between systems are critical elements in the operation of a broadcast station. Such hardware, usually passive, determines to a large extent the overall performance of the RF plant.

The mechanical and electrical characteristics of the transmission line, waveguide, RF combiners, and associated hardware that convey power from the transmitter to the antenna are critical to proper operation of any RF system. Mechanical considerations determine the ability of the components to withstand temperature extremes, lightning, rain, and wind. In other words, they determine the overall reliability of the system.

Skin Effect

The effective resistance offered by a given conductor to radio frequencies is considerably higher than the ohmic resistance measured with direct current. This is because of an action known as the skin effect, which causes the currents to be concentrated in certain parts of the conductor and leaves the remainder of the cross section to contribute little or nothing toward carrying the applied current.

When a conductor carries an alternating current, a magnetic field is produced that surrounds the wire. This field continually expands and contracts as the ac wave increases from zero to its maximum positive value and back to zero, then through its negative half-cycle. The changing magnetic lines of force cutting the conductor induce a voltage in the conductor in a direction that tends to retard the normal flow of current in...