Radio Frequency Bands

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Radio Frequencies / Electromagnetic Radiation

The yellow highlighted bands are radio frequencies plus the two bands used for WiFi and WiMax.
The lowest frequencies are not too useful for radio transmissions and the frequencies are more typical of audio and ultrasound systems.

The yellow highlighted areas are more likely to be in the exam.

	Name	Frequency Range	Wavelength Range	Comments
ELF	extremely low frequency	3 - 30 Hz	100 000 - 10 000 km	Efficient antennas are too big to be practicable.
SLF	superlow frequency	30 - 300 Hz	10 000 - 1000 km	Efficient antennas are too big to be practicable.
ULF	ultralow frequency	300 - 3000 Hz	1000 - 100 km	Efficient antennas are too big to be practicable.
VLF	very low frequency	3 - 30 kHz	100 - 10 km	Efficient antennas are too big to be practicable.
LF	low frequency	30 - 300 kHz	10 - 1 km	60kHz Time and Frequency Standard Long Wave Radio Band (AM Used)
MF	medium frequency	300 - 3000 kHz	1 km - 100 m	Medium Wave AM used
HF	high frequency	3 - 30 MHz	100 m - 10 m	Short Wave Radio Bands AM used Many digital modes are used on HF for text, image and data transmission.
VHF	very high frequency	30 - 300 MHz	10 - 1 m	FM Radio Band DAB Radio Band
UHF	ultrahigh frequency	300 - 3000 MHz	1m - 10 cm	TV Transmissions (low end) Mobile Phones (450 - 2000 MHz)
SHF	superhigh frequency	3 - 30 GHz	10 - 1 cm	WiMax Wireless Networking 2-11 and 10-66 GHz
EHF	extremely high frequency	30 - 300 GHz	1 cm - 1 mm	WiMax Wireless Networking 2-11 and 10-66 GHz
	Infra-Red	300 GHz - 4.3 x 10¹⁴ Hz		Warmth / Heat Radiation
	Visible Light	4.3 x 10¹⁴ - 7.5 x 10¹⁴ Hz		Commonly used for communication
	Ultra-Violet	7.5 x 10¹⁴ - 3 x 10¹⁷ Hz		Sun Burn - Harmful
	X-Rays	7.5 x 10¹⁴ - 3 x 10¹⁷ Hz		Hospital X Rays - Harmful
	Gamma-Rays	> 3 x 10¹⁹ Hz		Nuclear Reactions, Radiotherapy - Harmful
	Cosmic Rays	> 3 x 10²¹ Hz		Stellar and Galactic Events - Harmful

This image shows three AM stations with room for several more.
Each station is occupying about 9 kHz of the spectrum.
The transmitted audio has a bandwidth restricted to 4.5 kHz.
The channel spacing in this short wave band is 10 kHz. 9 kHz is usual on the LF and MF bands.

Also known as medium wave.
520 - 1610 kHz.
The channel spacing is 9kHz in Europe and 10kHz in the Americas.
Many broadcasters use this band.
Listeners prefer VHF or DAB because of better sound quality and reduced interference.

Also known as short wave.
1.711 - 30 MHz, subdivided into 15 bands used by broadcasters.
The other frequencies are used commercially and for services like shipping and air traffic control.
On trans-Atlantic flights, VHF links are good up to about 100 miles from the coast. After that HF radio has to be used. There are also satellite communications but aircraft safety always demands more than one system for safety critical systems.
The channel spacing is 5kHz.
Stations often interfere with each other.
These bands are good for longer distance communication.
Stations like the BBC World Service and Voice of Russia can be heard.

Some of the information in this image is correct.

Xkcd electromagnetic spectrum.png