Radio frequency

Radio frequency (RF) is the

• Energy from RF currents in conductors can radiate into space as
  electromagnetic waves (radio waves). This is the basis of radio
  technology.
• RF current does not penetrate deeply into electrical conductors but tends to flow along their surfaces; this is known as the skin effect.
• RF currents applied to the body often do not cause the painful sensation and muscular contraction of
  electric shock that lower frequency currents produce.^[4][5] This is because the current changes direction too quickly to trigger depolarization
  of nerve membranes. However, this does not mean RF currents are harmless; they can cause internal injury as well as serious superficial burns called RF burns.
• RF current can easily ionize air, creating a conductive path through it. This property is exploited by "high frequency" units used in electric arc welding, which use currents at higher frequencies than power distribution uses.
• Another property is the ability to appear to flow through paths that contain insulating material, like the
  capacitive reactance
  in a circuit decreases with increasing frequency.
• In contrast, RF current can be blocked by a coil of wire, or even a single turn or bend in a wire. This is because the
  inductive reactance
  of a circuit increases with increasing frequency.
• When conducted by an ordinary electric cable, RF current has a tendency to reflect from discontinuities in the cable, such as connectors, and travel back down the cable toward the source, causing a condition called standing waves. RF current may be carried efficiently over transmission lines such as coaxial cables.

Frequency bands

The radio spectrum of frequencies is divided into bands with conventional names designated by the International Telecommunication Union (ITU):

Frequency range	Wavelength range	ITU designation		IEEE bands[6]
		Full name	Abbreviation[7]
Below 3 Hz	>105 km			—
3–30 Hz	105–104 km	Extremely low frequency	ELF	—
30–300 Hz	104–103 km	Super low frequency	SLF	—
300–3000 Hz	103–100 km	Ultra low frequency	ULF	—
3–30 kHz	100–10 km	Very low frequency	VLF	—
30–300 kHz	10–1 km	Low frequency	LF	—
300 kHz – 3 MHz	1 km – 100 m	Medium frequency	MF	—
3–30 MHz	100–10 m	High frequency	HF	HF
30–300 MHz	10–1 m	Very high frequency	VHF	VHF
300 MHz – 3 GHz	1 m – 100 mm	Ultra high frequency	UHF	UHF, L, S
3–30 GHz	100–10 mm	Super high frequency	SHF	S, C, X, Ku, K, Ka
30–300 GHz	10–1 mm	Extremely high frequency	EHF	mm
300 GHz – 3 THz	1 mm – 0.1 mm	Tremendously high frequency	THF	—

Frequencies of 1 GHz and above are conventionally called

Applications

Communications

Radio frequencies are used in communication devices such as

Medicine

Medical applications of radio frequency (RF) energy, in the form of

Radio Frequency or RF energy is also being used in devices that are being advertised for weight loss and fat removal. The possible effects RF might have on the body and whether RF can lead to fat reduction needs further study. Currently, there are devices such as trusculpt ID, Venus Bliss and many others utilizing this type of energy alongside heat to target fat pockets in certain areas of the body. That being said, there is limited studies on how effective these devices are.

Measurement

Test apparatus for radio frequencies can include standard instruments at the lower end of the range, but at higher frequencies, the test equipment becomes more specialized.^{[13][citation needed] [14]}

Mechanical oscillations

While RF usually refers to electrical oscillations, mechanical RF systems are not uncommon: see

See also

• Amplitude modulation (AM)
• Bandwidth (signal processing)
• Electromagnetic interference
• Electromagnetic radiation
• Electromagnetic spectrum
• EMF measurement
• Frequency allocation
• Frequency modulation (FM)
• Plastic welding
• Pulsed electromagnetic field therapy
• Spectrum management

References