Friday, March 11, 2005

Radio Frequency

Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. Such frequencies account for the following parts of the spectrum:

  • Extremely low frequency ELF 1 3–30 Hz 100,000 km – 10,000 km
  • Super low frequency SLF 2 30–300 Hz 10,000 km – 1000 km
  • Ultra low frequency ULF 3 300–3000 Hz 1000 km – 100 km
  • Very low frequency VLF 4 3–30 kHz 100 km – 10 km
  • Low frequency LF 5 30–300 kHz 10 km – 1 km
  • Medium frequency MF 6 300–3000 kHz 1 km – 100 m
  • High frequency HF 7 3–30 MHz 100 m – 10 m
  • Very high frequency VHF 8 30–300 MHz 10 m – 1 m
  • Ultra high frequency UHF 9 300–3000 MHz 1 m – 100 mm
  • Super high frequency SHF 10 3–30 GHz 100 mm – 10 mm
  • Extremely high frequency EHF 11 30–300 GHz 10 mm – 1 mm

Note: above 300 GHz, the absorption of electromagnetic radiation by Earth's atmosphere is so great that the atmosphere is effectively opaque to higher frequencies of electromagnetic radiation, until the atmosphere becomes transparent again in the so-called infrared and optical window frequency ranges.

The ELF, SLF, ULF, and VLF bands overlap the AF (audio frequency) spectrum, which is approximately 20–20,000 Hz. However, sounds are transmitted by atmospheric compression and expansion, and not by electromagnetic energy.

Electrical connectors designed to work at radio frequencies are known as RF connectors. RF is also the name of a standard audio/video connector, also called BNC (Bayonet Neill-Concelman).

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