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What radio frequencies are used for what purposes?
The Federal Communications Commission (FCC) licenses the frequency spectrum in the United States.
Useful charts showing frequency allocations are available from the National Telecommunications and Information Administration (NTIA) at http://www.ntia.doc.gov/osmhome/allochrt.html.
This table shows commonly used names for various frequency ranges:
| Frequency | Description |
|---|---|
| 30 - 300 GHz | Extremely High Frequency |
| 3 - 30 GHz | Super High Frequency |
| 300 MHz - 3 GHz | Ultra High Frequency (UHF) |
| 30 - 300 MHz | Very High Frequency (VHF) |
| 3 - 30 MHz | High Frequency (HF) |
| 300 KHz - 3 MHz | Medium Frequency |
| 30 KHz - 300 KHz | Low Frequency (LF) |
| 3 - 30 KHz | Very Low Frequency (VLF) |
| 300 Hz - 3 KHz | Voice Frequency |
| Below 300 Hz | Extremely Low Frequency |
Uses of Radio Frequencies
The VLF range is used for long-distance worldwide telegraphy and submarine communication. In the VLF frequency range, radio waves propagates as in a waveguide, using the earthÂ's surface and the ionosphere as boundaries. Attenuation is comparatively low in the VLF range, which is useful for very long distance radio communications.
The LF frequency range is used for standard AM broadcasting. Propagation in the LF band is by means of surface wave due to the presence of the ground.
The HF range is used for long-range broadcasting services via sky wave reflection and refraction by the ionosphere. The HF range experiences difficulties due to fluctuations in the ionosphere.
Frequencies at VHF and higher ranges allow for line-of-sight space wave propagation. At these frequencies, concern must be taken to plan for wave reflection from the ground, refraction by the troposphere, scattering by atmospheric hydrometeors, and multipath effects of natural and man-made topographical features.
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