Chapter 11 / 11.4 / 11.4.2

11.4.2 Frequency Of Operation

Figure 11.16 illustrates that the effectiveness of surface-wave propagation decreases as frequency increases. For this reason, surface-wave systems are typically confined to the LF and MF bands, and rarely operate above approximately 2–5 MHz. At higher frequencies, raising the antenna height and employing space-wave propagation generally provides better performance.

Although attenuation decreases as frequency is lowered, atmospheric noise increases at lower frequencies, particularly in the LF and MF bands. An operating frequency must therefore be selected as a compromise between propagation range and noise environment.