Redirected from VHF
Very high frequency (VHF) radio signals are on frequencies between 30 and 300 megahertz (wavelengths of 10 and 1 metre respectively). The general
description of frequencies immediately lower VHF is HF, and the
next higher frequencies as known as ultra-high frenquencies (UHF). UHF and VHF are the most common frequency bands for television.
VHF frequencies' propagation characteristics are ideal for
short-distance terrestrial communication. Unlike HF frequencies, the
ionosphere does not reflect VHF radio (except on rare occasions
during solar flares) 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 that
operated by taxis and police), marine two-way audio communications,
and aircraft radios.
The large slice of 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 Britain colour television transmissions began on UHF in the late 1960s, instantly rendering VHF obsolete. The last British VHF TV transmitters closed down in 1986.