The usable spectrum of electromagnetic radiation frequencies extends over a range from below 100 Hz for power distribution to 10 ²⁰ Hz for the shortest X rays. The lower frequencies are used primarily for terrestrial broadcasting and communications. The higher frequencies include visible and near-visible infrared and ultraviolet light, and X rays. The frequencies typically of interest to RF engineers range from 30 kHz to 30 GHz.

Low Frequency (LF): 30 to 300 kHz

The LF band is used for around-the-clock communications services over long distances and where adequate power is available to overcome high levels of atmospheric noise. Applications include:

• Radionavigation

• Fixed/maritime communications and navigation

• Aeronautical radionavigation

• Low-frequency broadcasting (Europe)

• Underwater submarine communications (up to about 30 kHz)

Medium Frequency (MF): 300 kHz to 3 MHz

The low-frequency portion of this band is used for around-the-clock communication services over moderately long distances. The upper portion of the MF band is used principally for moderate-distance voice communications. Applications in this band include:

• AM radio broadcasting (535.5 to 1605.5 kHz)

• Radionavigation

• Fixed/maritime communications

• Aeronautical radionavigation

• Fixed and mobile commercial communications

• Amateur radio

• Standard time and frequency services

High Frequency (HF): 3 to 30 MHz

This band provides reliable medium-range coverage during daylight and, when the transmission path is in total darkness, worldwide long-distance service. The reliability and signal...