Radio frequency

From Wikipedia, the free encyclopedia

Radio frequency (RF) is a frequency or rate of oscillation within the range of about 3 Hz to 300 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves. Since most of this range is beyond the vibration rate that most mechanical systems can respond to, RF usually refers to oscillations in electrical circuits or electromagnetic radiation.

Contents 1 Special properties of RF electrical signals 2 Frequencies 3 See also 4 External links

[edit] Special properties of RF electrical signals

Electrical currents that oscillate at RF have special properties not shared by direct current signals. One such property is the ease with which it can ionize air to create a conductive path through air. This property is exploited by 'high frequency' units used in electric arc welding. Another special property is an electromagnetic force that drives the RF current to the surface of conductors, known as the skin effect. Another property is the ability to appear to flow through paths that contain insulating material, like the dielectric insulator of a capacitor. The degree of effect of these properties depends on the frequency of the signals.

[edit] Frequencies

Name	Symbol	Frequency	Wavelength	Applications
Extremely low frequency	ELF	a 3 to 30 Hz	k 10,000 km to 100,000 km	audible 20+ Hz, communication with submarines
Super low frequency	SLF	b 30 to 300 Hz	j 1,000 km to 10,000 km	audible, AC power grids (50 hertz and 60 hertz)
Ultra low frequency	ULF	c 300 to 3000 Hz	i 100 to 1000 km	audible, communication with mines
Very low frequency	VLF	d 3 to 30 kHz	h 10 to 100 km	audible range 20 Hz to 20 kHz (to be audible, energy must be simply converted to sound)
Low frequency	LF	e 30 to 300 kHz	g 1 to 10 km	international broadcasting, navigational beacons, lowFER
Medium frequency	MF	f 300 to 3000 kHz	f 100 m to 1 km	navigational beacons, AM broadcasting, maritime and aviation communication
High frequency	HF	g 3 to 30 MHz	e 10 to 100 m	shortwave, citizens' band radio
Very high frequency	VHF	h 30 to 300 MHz	d 1 to 10 m	FM broadcasting, broadcast television, aviation
Ultra high frequency	UHF	i 300 to 3000 MHz	c 10 to 100 cm	broadcast television, mobile telephones, wireless networking, microwave ovens
Super high frequency	SHF	j 3 to 30 GHz	b 1 to 10 cm	wireless networking, satellite links.
Extremely high frequency	EHF	k 30 to 300 GHz	a 1 to 10 mm	microwave data links, radio astronomy, remote sensing, advanced weapons systems, advanced security scanning

[edit] See also

• Radio waves
• Plastic Sealing/Welding Technologies
• Ultrasound

[edit] External links

• Definition of frequency bands (VLF, ELF … etc.) IK1QFK Home Page (vlf.it)
• Radio, light, and sound waves, conversion between wavelength and frequency
• RF eBooks - Some free RF related eBooks
• RF and Telecommunication eBooks
• RF Terms Glossary

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