Band I

Band I is a range of radio frequencies within the very high frequency (VHF) part of the electromagnetic spectrum. Band I ranges from 47 to 68 MHz for the European Broadcasting Area,[1] and from 54 to 88 MHz for the Americas[2] and it is primarily used for television broadcasting in line to ITU Radio Regulations (article 1.38). Channel spacings vary from country to country, with spacings of 6, 7 and 8 MHz being common.

Television broadcasting usage

In the UK, Band I was originally used by the BBC for monochrome 405-line television;[3] likewise, the French former 455-line (1937-1939) then 441-line (1943-1956) transmitter on the Eiffel Tower in Paris, and some stations of the French monochrome 819-line system used Band I. Both 405-line and 819-line systems were discontinued in the mid-1980s. Other European countries used and still use Band I for 625-line analogue television, first in monochrome and later in colour.

This is now being gradually phased out with the introduction of digital television in the DVB-T standard, which is not defined for VHF Band I, though some older receivers and some modulators do support it.

In the United States, use of this band is for analog NTSC (ended June 12, 2009) and digital ATSC (current). Digital television has problems with impulse noise interference, particularly in this band.

Europe

In European countries that use System B for television broadcasting, the band is subdivided into three channels, each being 7 MHz wide:

Channel Frequency Range
E247-54 MHz
E2A48.5-55.5 MHz
E354-61 MHz
E461-68 MHz
C82.25-87.75 MHz

Italy also uses a "outband" "channel C" (video : 82.25 MHz - audio : 87.75 MHz). It was used by the first transmitter brought in service by the RAI in Torino in the Fifties which was previously used in WW2 by the US to broadcast NTSC TV on channel A6 for military purposes, later donated to Italy, it had its video carrier shifted 1 MHz lower to accommodate the System B standard. This channel was also widely used by private local stations until the switch over to DVB-T.

Some countries use slightly different frequencies or don't use Band 1 at all for terrestrial broadcast television. The fast growing of digital television as well as the susceptibility of this band to interference during E skip events in all European countries is accompanied by the progressive closedown of band I analog transmitters, e.g. former French-language Swiss Television transmitter at La Dôle near Geneva on channel E4 or French analog transmitters used by Canal Plus for its Pay-TV VHF network, e.g. Besançon (Lomont) and Carcassonne (Pic de Nore) both on French channel "L-3".

Russia and other former members of OIRT

In the countries that use System D television broadcast system, the channel allocation in the VHF-I band is as follows:

Channel Frequency Range
148.5-56.5 MHz
258-66 MHz

North America

The band is subdivided into five channels for television broadcasting, each occupying 6 MHz (System M). Channel 1 is not being used for broadcasting anymore.

Channel Frequency Range
1*44-50 MHz
A254-60 MHz
A360-66 MHz
A466-72 MHz
A576-82 MHz
A682-88 MHz
A6A81.5-87.5 MHz

FM Radio Usage

The upper end of this band, 87.5 to 88 MHz, is the lower end of the FM radio band. In the United States, the FCC will occasionally issue a license for 87.9 MHz (though it only does so on rare occurrences and special circumstances; KSFH is the only standalone station that uses 87.9 currently); 87.7, which is approximately the same frequency as the audio feed of channel 6, is used by some television licenses to broadcast primarily to radio, such as Pulse 87's stations.

See also

References

  1. ↑ "FM / TV Regional Frequency Assignment Plans". ITU. Retrieved 20 February 2017.
  2. ↑ "Frequency Bands allocated to Terrestrial Broadcasting Services". ITU. Retrieved 20 February 2017.
  3. ↑ Paulu, Burton (1981-10-01). Television and Radio in the United Kingdom. U of Minnesota Press. p. 91. ISBN 9780816609413. Retrieved 11 April 2012.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.