From TheBestLinks.com
Very high frequency (VHF) is the radio frequency range from 30 MHz (wavelength 10 m) to 300 MHz (wavelength 1 m).
Common uses for VHF are FM radio broadcast at 88-108 MHz and television broadcast (together with UHF). VHF is also commonly used for terrestrial navigation systems (VOR in particular) and aircraft communications.
The general description of frequencies immediately below VHF is HF, and the next higher frequencies are known as Ultra high frequency (UHF). UHF and VHF are the most common frequency bands for television.
VHF frequencies' propagation characteristics are ideal for short-distance terrestrial communication. Unlike high frequencies (HF), the ionosphere does not usually reflect VHF radio and thus transmissions are restricted to the local area (and can't interfere with transmissions thousands of kilometres away) It is also less affected by atmospheric noise and interference from electrical equipment than low frequencies. Whilst it is more easily blocked by land features than HF and lower
frequencies, it is less bothered by buildings and other less substantial objects than higher frequencies. It was also easier to construct efficient transmitters, receivers, and antennas for it in the earlier days of radio. In most countries, the VHF spectrum is used for broadcast audio and
television, as well as commercial two-way radios (such as those operated by taxis and police), marine two-way audio communications, and aircraft radios.
The large technically and commercially valuable slice of the VHF spectrum taken up by television transmission has attracted the attention of many companies and governments recently, with the development of more efficient digital television broadcasting standards. In some countries much of this spectrum will likely become available (probably for sale) in the next decade or so (currently scheduled for 2008 in the United States).
In the United Kingdom, the authorities chose to develop colour television exclusively on UHF, beginning in the late 1960s. The last British VHF TV transmitters closed down on January 3rd, 1985. VHF band III is now used in the UK for digital audio broadcasting.
New Zealand
- Band I: 45~68 MHz (Television)
- Band II: 88~108 MHz (Radio)
- Band III: 175~225MHz (Television)
In New Zealand, the four main Free-to-Air TV stations still use the VHF Television bands (Band I and Band III) to transmit their programmes to New Zealand households. Other stations, including a variety of pay and regional free-to-air stations, broadcast their programmes using the UHF band since the VHF band is very overloaded with four stations sharing a very small frequency band.
da:VHF
fr:VHF III
ja:超短波
nl:VHF
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