Radio Wave Characteristics and Frequency Spectrum

• An electromagnetic wave travels through space, sometimes referred to as a radio wave, which is an energy form that is radiated outward from a source.
• Electromagnetic radiation is a self-propagating wave that consists of electric and magnetic field components that vibrate perpendicularly to each other along the direction of propagation.
• A radio wave consists of repeating cycles of electric and magnetic field intensities.

Radio Wave Characteristics

• Frequency is the measurement of the cycles completed in one second (1 Hertz=1 cycle per second); the higher the frequency, the more information that can be transmitted.
• Radio stations use electromagnetic waves that oscillate at a specific frequency, measured in units of Hertz (Hz).
• Wavelength is the distance between two points on the wave that have similar characteristics.

Radio Frequency Spectrum

• Extremely Low Frequency, or ELF, extends from 3 – 30 Hz
• Voice frequency, or VF, extends from 300 – 3000 Hz
• Very Low Frequency, or VLF, extends from 3 – 30 kHz
• Low Frequency, or LF, extends from 30 – 300 kHz
• Medium Frequency, or MF, extends from 300 – 3000 kHz
• High Frequency, or HF, extends from 3 – 30 MHz
• Very High Frequency, or VHF, extends from 30 – 300 MHz
• Ultra High Frequency, or UHF, extends from 300 – 3000 MHz
• Super High Frequency, or SHF, extends from 3 – 30 GHz
• Extremely High Frequency, or EHF, extends from 30 – 300 GHz

Signal Characteristics

• Radio signal characteristics include amplitude, wavelength, and frequency, among others.
• The amplitude of a wave is a measure of its strength (height).
• Wavelength is the distance between two points on the wave that have similar characteristics.
• Phase refers to the position of a point in time (an instant) on a waveform cycle.
• Polarization is the physical orientation of the electric field in radio waves.
• Radio waves that travel along the ground are called ground waves.
• Radio waves that are radiated outward from the antenna are called space waves.
• Radio waves that are reflected or refracted back to the Earth from the ionosphere are called sky waves.
• Atmospheric conditions can cause radio signals to be ducted over distances far beyond normal.