Radio wave

Radio waves are electromagnetic waves occurring on the radio frequency portion of the electromagnetic spectrum.

File:RadioWaves.jpg

Diagram of the electric (E) and magnetic (H) fields of Radio Waves emanating from a radio transmitting antenna (small dark vertical line in the center). The E and H fields are perpendicular as implied by the phase diagram in the lower right.

Discovery and utilization

Main article: History of radio

Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including radio waves.

Radio waves were first predicted by mathematical work done in 1865 by James Clerk Maxwell. Maxwell noticed wavelike properties of light and similarities in electrical and magnetic observations. He then proposed equations, that described light waves and radio waves as waves of electromagnetism that travel in space. In 1887, Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic waves by experimentally generating radio waves in his laboratory. Many inventions followed, making practical the use of radio waves to transfer information through space.

Nikola Tesla and Guglielmo Marconi are credited with inventing systems to allow radio waves to be used for communication.

Radio portion of the electromagnetic spectrum

Radio waves are divided up into bands by frequency (and corresponding wavelength) as shown in the radio frequency spectrum table below.

Band name	Abbr	ITU band	Frequency and Wavelength in air	Example uses
subHertz	subHz	0	< 3 Hz > 100,000 km	Natural and man-made electromagnetic waves millihertz, microhertz, nanohertz from earth, ionosphere, sun, planets, etc
Extremely low frequency	ELF	1	3–30 Hz 100,000 km – 10,000 km	Communication with submarines
Super low frequency	SLF	2	30–300 Hz 10,000 km – 1000 km	Communication with submarines
Ultra low frequency	ULF	3	300–3000 Hz 1000 km – 100 km	Communication within mines
Very low frequency	VLF	4	3–30 kHz 100 km – 10 km	Submarine communication, avalanche beacons, wireless heart rate monitors, geophysics
Low frequency	LF	5	30–300 kHz 10 km – 1 km	Navigation, time signals, AM longwave broadcasting, RFID
Medium frequency	MF	6	300–3000 kHz 1 km – 100 m	AM (Medium-wave) broadcasts
High frequency	HF	7	3–30 MHz 100 m – 10 m	Shortwave broadcasts, amateur radio and over-the-horizon aviation communications, RFID
Very high frequency	VHF	8	30–300 MHz 10 m – 1 m	FM, television broadcasts and line-of-sight ground-to-aircraft and aircraft-to-aircraft communications. Land Mobile and Maritime Mobile communications
Ultra high frequency	UHF	9	300–3000 MHz 1 m – 100 mm	television broadcasts, microwave ovens, mobile phones, wireless LAN, Bluetooth, GPS and Two-Way Radios such as Land Mobile, FRS and GMRS Radios
Super high frequency	SHF	10	3–30 GHz 100 mm – 10 mm	microwave devices, wireless LAN, most modern Radars
Extremely high frequency	EHF	11	30–300 GHz 10 mm – 1 mm	Radio astronomy, high-speed microwave radio relay
			Above 300 GHz < 1 mm

Notes

• 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.
• The SHF and EHF bands are sometimes not considered to be a part of the radio spectrum, forming their own microwave spectrum.

Named frequency bands

General

Broadcast Frequencies:

• Longwave AM Radio = 148.5 - 283.5 kHz (LF)
• Mediumwave AM Radio = 530 kHz - 1710 kHz (MF)
• Shortwave AM Radio = 3 MHz - 30 MHz (HF)
• TV Band I (Channels 2 - 6) = 54 MHz - 88 MHz (VHF)
• FM Radio Band II = 88 MHz - 108 MHz (VHF)
• TV Band III (Channels 7 - 13) = 174 MHz - 216 MHz (VHF)
• TV Bands IV & V (Channels 14 - 69) = 470 MHz - 806 MHz (UHF) [1]

For more information see the NTIA frequency allocation chart: http://www.ntia.doc.gov/osmhome/allochrt.html

Amateur radio frequencies

The range of allowed amateur radio frequencies vary between countries. The article Amateur radio frequency allocations lists frequencies allocated for amateur radio use.

IEEE US

Per IEEE Std 521-2002. Reaffirmed standard of 1984; originally dates back to WWII.

Band	Frequency range	Origin of name
HF band	3 to 30 MHz	High Frequency
VHF band	30 to 300 MHz	Very High Frequency
UHF band	300 to 1000 MHz	Ultra High Frequency Frequencies from 216 to 450 MHz were sometimes called P-band: Previous, since early British radar used this band but later switched to higher frequencies.
L band	1 to 2 GHz	Long wave
S band	2 to 4 GHz	Short wave
C band	4 to 8 GHz	Compromise between S and X
X band	8 to 12 GHz	Used in WW II for fire control, X for cross (as in crosshair)
Ku band	12 to 18 GHz	Kurz-under
K band	18 to 27 GHz	German Kurz (short)
Ka band	27 to 40 GHz	Kurz-above
V band	40 to 75 GHz
W band	75 to 110 GHz	W follows V in the alphabet
mm band	110 to 300 GHz

EU, NATO, US ECM frequency designations

Band	Frequency range
A band	0 to 0.25 GHz
B band	0.25 to 0.5 GHz
C band	0.5 to 1.0 GHz
D band	1 to 2 GHz
E band	2 to 3 GHz
F band	3 to 4 GHz
G band	4 to 6 GHz
H band	6 to 8 GHz
I band	8 to 10 GHz
J band	10 to 20 GHz
K band	20 to 40 GHz
L band	40 to 60 GHz
M band	60 to 100 GHz

Waveguide frequency bands

Band	Frequency range
R band	1.70 to 2.60 GHz
D band	2.20 to 3.30 GHz
S band	2.60 to 3.95 GHz
E band	3.30 to 4.90 GHz
G band	3.95 to 5.85 GHz
F band	4.90 to 7.05 GHz
C band	5.85 to 8.20 GHz
H band	7.05 to 10.10 GHz
X band	8.2 to 12.4 GHz
Ku band	12.4 to 18.0 GHz
K band	15.0 to 26.5 GHz
Ka band	26.5 to 40.0 GHz
Q band	33 to 50 GHz
U band	40 to 60 GHz
V band	50 to 75 GHz
W band	75 to 110 GHz
Y band	325 to 500 GHz

References

• ITU-R Recommendation V.431: Nomenclature of the frequency and wavelength bands used in telecommunications. International Telecommunication Union, Geneva.
• IEEE Standard 521-2002: Standard Letter Designations for Radar-Frequency Bands
• AFR 55-44/AR 105-86/OPNAVINST 3430.9A/MCO 3430.1, 27 October 1964 superseded by AFR 55-44/AR 105-86/OPNAVINST 3430.1A/MCO 3430.1A, 6 December 1978: Performing Electronic Countermeasures in the United States and Canada, Attachment 1,ECM Frequency Authorizations.

See also

• Frequency allocation
• Radio astronomy
• Radio electronics
• Radio propagation

References

• PBS, Tesla - Who Invented Radio?
• James Clerk Maxwell, "A Dynamical Theory of the Electromagnetic Field", Philosophical Transactions of the Royal Society of London 155, 459-512 (1865).
• Heinrich Hertz: "Electric waves; being researches on the propagation of electric action with finite velocity through space" (1893). Cornell University Library Historical Monographs Collection. Reprinted by Cornell University Library Digital Collections