The Carrier Wave

Author: J.B. Hoag

When an alternating current flows back and forth in a wire, magnetic and electric fields are constantly forming around the wire, collapsing, reforming in the opposite direction, collapsing, etc. Some of the energy in the fields does not return to the wires but travels outward as a " radio " wave. Although small at low, audio frequencies, the loss of energy from the circuit into the radiated waves increases as the frequency is increased. The form of the radiated wave, which is also the form of the currents or of the voltages in the wire, is shown in Fig. 16 A.

Fig. 16 A. A carrier wave

It will be noted (dotted lines) that the strength or amplitude of this curve does not change. It is called a carrier wave because it serves to carry a signal from the transmitter to the receiver.