Very high frequency

VHF television antennas used for broadcast television reception. These six antennas are a type known as a Yagi antenna, which is widely used at VHF frequencies

Very high frequency (VHF) is the ITU-designated range ^[1] of radio frequency electromagnetic waves from 30 MHz to 300 MHz, with corresponding wavelengths of one to ten meters. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).

Common uses for VHF are FM radio broadcasting, television broadcasting, land mobile stations (emergency, business, private use and military), long range data communication up to several tens of kilometres with radio modems, amateur radio, and marine communications. Air traffic control communications and air navigation systems (e.g. VOR, DME & ILS) work at distances of 100 kilometres or more to aircraft at cruising altitude.

Propagation characteristics

VHF propagation characteristics are ideal for short-distance terrestrial communication, with a range generally somewhat farther than line-of-sight from the transmitter (see formula below). Unlike high frequencies (HF), the ionosphere does not usually reflect VHF waves (called skywave propagation) so transmissions are restricted to the local radio horizon less than 100 miles. VHF is also less affected by atmospheric noise and interference from electrical equipment than lower frequencies. While it is blocked by land features such as hills and mountains, it is less affected by buildings and can be received indoors, although multipath television reception due to reflection from buildings can be a problem in urban areas

Line-of-sight calculation

For analog TV, VHF transmission range is a function of transmitter power, receiver sensitivity, and distance to the horizon, since VHF signals propagate under normal conditions as a near line-of-sight phenomenon. The distance to the radio horizon is slightly extended over the geometric line of sight to the horizon, as radio waves are weakly bent back toward the Earth by the atmosphere.

An approximation to calculate the line-of-sight horizon distance (on Earth) is:

• distance in nautical miles = where is the height of the antenna in feet ^{[citation needed]}
• distance in kilometres = where is the height of the antenna in metres. ^{[citation needed]}

These approximations are only valid for antennas at heights that are small compared to the radius of the Earth. They may not necessarily be accurate in mountainous areas, since the landscape may not be transparent enough for radio waves.

In engineered communications systems, more complex calculations are required to assess the probable coverage area of a proposed transmitter station.^{[citation needed]}

The accuracy of these calculations for digital TV signals is being debated.^[2]

Antennas

VHF is the first band at which wavelengths are small enough to make efficient transmitting antennas for handheld devices, so the VHF and UHF wavelengths are used for handheld transceivers and walkie talkies. Fixed station antennas are usually based on the dipole, while portable radios usually use whips or rubber ducky antennas. The Yagi antenna is the most widely used as a high gain or "beam" antenna. Helical and turnstile antennas are used for satellite communication since they employ circular polarization. For even higher gain, multiple Yagis or helicals can be mounted together as an array antennas. Television and FM broadcasting stations use collinear arrays of specialized dipole antennas such as batwing antennas.

Universal use

Certain subparts of the VHF band have the same use around the world. Some national uses are detailed below.

• 108–118 MHz: Air navigation beacons VOR and Instrument Landing System localiser.
• 118–137 MHz: Airband for air traffic control, AM, 121.5 MHz is emergency frequency
• 144–146 MHz: Amateur radio. In some countries 144–148 MHz.

By country

A plan showing VHF use in television, FM radio, amateur radio, marine radio and aviation.

Australia

The VHF TV band in Australia was originally allocated channels 1 to 10 - with channels 2, 7 and 9 assigned for the initial services in Sydney and Melbourne, and later the same channels were assigned in Brisbane, Adelaide and Perth. Other capital cities and regional areas used a combination of these and other frequencies as available. The initial commercial services in Hobart and Darwin were respectively allocated channels 6 and 8 rather than 7 or 9.

By the early 1960s it became apparent that the 10 VHF channels were insufficient to support the growth of television services. This was rectified by the addition of three additional frequencies - channels 0, 5A and 11. Older television sets using rotary dial tuners required adjustment to receive these new channels. Most TVs of that era were not equipped to receive these broadcasts, and so were modified at the owners' expense to be able to tune into these bands; otherwise the owner had to buy a new TV.

Several TV stations were allocated to VHF channels 3, 4 and 5, which were within the FM radio bands although not yet used for that purpose. A couple of notable examples were NBN-3 Newcastle, WIN-4 Wollongong and ABC Newcastle on channel 5. While some Channel 5 stations were moved to 5A in the 1970s and 80s, beginning in the 1990s, the Australian Broadcasting Authority began a process to move these stations to UHF bands to free up valuable VHF spectrum for its original purpose of FM radio. In addition, by 1985 the federal government decided new TV stations are to be broadcast on the UHF band.

Two new VHF frequencies, 9A and 12, have since been made available and are being used primarily for digital services (e.g. ABC in capital cities) but also for some new analogue services in regional areas. Because channel 9A is not used for television services in or near Sydney, Melbourne, Brisbane, Adelaide or Perth, digital radio in those cities are broadcast on DAB frequencies blocks 9A, 9B and 9C.

Refer to Australasian television frequencies for more information.

New Zealand

• 44–51, 54–68 MHz: Band I Television (channels 1–3)
• 87.5–108 MHz: Band II Radio
• 174–230 MHz: Band III Television (channels 4–11)

In New Zealand, the four main Free-to-Air TV stations still use the VHF Television bands (Band I and Band III) to transmit to New Zealand households. Other stations, including a variety of pay and regional free-to-air stations, are forced to broadcast in the UHF band, since the VHF band is very overloaded with four stations sharing a very small frequency band, which can be so overcrowded that one or more channels, more often than not one of the MediaWorks-owned channels (TV3 and FOUR), is unavailable in some smaller towns.

However, by the end of 2013, there will be no television channels broadcasting on the VHF bands.^[3]

Refer to Australasian television frequencies for more information.

United Kingdom

British television originally used VHF band I and band III. Television on VHF was in black and white with 405-line format (although there were experiments with all three colour systems—NTSC, PAL, and SECAM—adapted for the 405-line system in the late 1950s and early 60s).

British colour television was broadcast on UHF (channels 21–69), beginning in the late 1960s. From then on, TV was broadcast on both VHF and UHF (VHF being a monochromatic downconversion from the 625-line colour signal), with the exception of BBC2 (which had always broadcast solely on UHF). The last British VHF TV transmitters closed down on January 3, 1985. VHF band III is now used in the UK for digital audio broadcasting, and VHF band II is used for FM radio, as it is in most of the world.

Unusually, the UK has an amateur radio allocation at 4 metres, 70-70.5 MHz.

United States and Canada

Frequency assignments between US and Canadian users are closely coordinated since much of the Canadian population is within VHF radio range of the US border. Certain discrete frequencies are reserved for radio astronomy. The general services in the VHF band are:

• 7-1001 MHz: Cable TV
• 30–46 MHz: Licensed 2-way land mobile communication.^[4]
• 30–88 MHz: Military VHF-FM, including SINCGARS
• 43–50 MHz: Cordless telephones, 49 MHz FM walkie-talkies and radio controlled toys, and mixed 2-way mobile communication. The FM broadcast band originally operated here (42-50 MHz) before moving to 88-108 MHz.
• 50–54 MHz: Amateur radio 6 meters band
• 54-72 and 76-88 MHz TV channels 2 through 6 (VHF-Lo), known as "Band I" internationally; some DTV stations will appear here. See North American broadcast television frequencies
• 72–76 MHz: Radio controlled models, industrial remote control, and other devices. Model aircraft operate on 72 MHz while surface models operate on 75 MHz in the USA and Canada, air navigation beacons 74.8-75.2 MHz.
• 87.5–108 MHz: FM radio broadcasting (87.5–91.9 non-commercial, 92–108 commercial in the United States) (known as "Band II" internationally)
• 108–118 MHz: Air navigation beacons VOR
• 118–137 MHz: Airband for air traffic control, AM, 121.5 MHz is an emergency frequency
• 137-138 Space research, space operations, meteorological satellite ^[5]
• 138–144 MHz: Land mobile, auxiliary civil services, satellite, space research, and other miscellaneous services
• 144–148 MHz: Amateur radio 2 Meters band
• 148-150 MHz: Land mobile, fixed, satellite
• 150–156 MHz: "VHF business band," public safety, the unlicensed Multi-Use Radio Service (MURS), and other 2-way land mobile, FM
• 156–158 MHz VHF Marine Radio; narrow band FM, 156.8 MHz (Channel 16) is the maritime emergency and contact frequency.
• 159.81-161.565 MHz Railways ^[6] 159.81-160.2 are railroads in Canada only and is used by trucking companies in the U.S.
• 160.6-162 Wireless microphones and TV/FM broadcast remote pickup
• 162.40–162.55: NOAA Weather Stations, narrowband FM
• 174-216 MHz television channels 7 - 13 (VHF-Hi), known as "Band III" internationally. A number of DTV channels have begun broadcasting here, especially many of the stations which were assigned to these channels for previous analog operation.
• 174–216 MHz: professional wireless microphones (low power, certain exact frequencies only)
• 216–222 MHz: land mobile, fixed, maritime mobile,^[7]
• 222–225 MHz: 1.25 meters (US) (Canada 219-220, 222-225 MHz) amateur radio
• 225 MHz and above: Military aircraft radio, 243 MHz is an emergency frequency (225–400 MHz) AM, including HAVE QUICK, dGPS RTCM-104

VHF television

The U.S. FCC's added television to the VHF band in 1941 on channels one through six. During World War II, channel one was removed and used only for war purposes. (It later became the 6 meter amateur band.) In 1945, channels seven through thirteen were added.^[8]

The development of arguably more efficient digital television broadcasting standards to replace VHF television has made the large technically and commercially valuable slice of the VHF spectrum formerly taken up by television broadcasting available for relicensing or sale after a transition period, which ended June 12, 2009 in the United States; see Effect on existing analog technology for dates in other countries.

87.5-87.9 MHz

87.5-87.9 MHz is a radio frequency which, in most of the world, is used for FM broadcasting. In North America, however, this bandwidth is allocated to VHF television channel 6 (82-88 MHz). The analog audio for TV channel 6 is broadcast at 87.75 MHz (adjustable down to 87.74). Several stations, most notably those joining the Pulse 87 franchise, have operated on this frequency as radio stations, though they use television licenses. As a result, FM radio receivers such as those found in automobiles which are designed to tune into this frequency range could receive the audio for analog-mode programming on the local TV channel 6 while in North America.

87.9 MHz is normally off-limits for FM audio broadcasting except for displaced class D stations which have no other frequencies in the normal 88.1-107.9 MHz subband on which to move. So far, only 2 stations have qualified to operate on 87.9 MHz: 10-watt KSFH in Mountain View, California and 34-watt translator K200AA in Sun Valley, Nevada.

Unlicensed operation

In some countries, particularly the United States and Canada, limited low-power license-free operation is available in the FM broadcast band for purposes such as micro-broadcasting and sending output from CD or digital media players to radios without auxiliary-in jacks, though this is illegal in some other countries. This practice was legalised in the United Kingdom on 8 December 2006.^[9]

See also

• Marine VHF radio
• List of oldest radio stations
• Apex (radio band)
• FM broadcast band
• Moving image formats
• Polar mesosphere summer echoes
• Television channel frequencies
• Knife-edge effect
• Instrument Landing System
• VHF omnidirectional range

References

v t e Telecommunications History Beacon Broadcasting Communications satellite Computer network Drums Electrical telegraph Fax Heliographs Hydraulic telegraph Internet Mass media Mobile phone Optical telecommunication Optical telegraphy Photophone Prepaid mobile phone Radio Radiotelephone Satellite communications Smoke signals Telecommunications history Telegraphy Telephone The Telephone Cases Television Timeline of communication technology Undersea telegraph line Videoconferencing Videophone Videotelephony Pioneers Edwin Howard Armstrong John Logie Baird Alexander Graham Bell Tim Berners-Lee Jagadish Chandra Bose Vint Cerf Claude Chappe Lee De Forest Philo Farnsworth Reginald Fessenden Elisha Gray Guglielmo Marconi Alexander Stepanovich Popov Johann Philipp Reis Nikola Tesla Camille Papin Tissot Alfred Vail Charles Wheatstone Vladimir K. Zworykin Network topology Links Nodes Terminal node Transmission media Coaxial cable Free-space optical Optical fiber Radio waves Telephone lines Terrestrial microwave Switching Circuit switching Packet switching Telephone exchange Network switch Multiplexing Space-division multiplexing Frequency-division multiplexing Time-division multiplexing Polarization-division multiplexing Orbital angular momentum multiplexing Code division multiplexing Networks ARPANET BITNET Computer Ethernet FidoNet Internet ISDN LAN Mobile NGN Public Switched Telephone Radio Telecommunications equipment Television Telex WAN Wireless World Wide Web Geographic v t e Telecommunications in Africa Sovereign states Algeria Angola Benin Botswana Burkina Faso Burundi Cameroon Cape Verde Central African Republic Chad Comoros Democratic Republic of the Congo Republic of the Congo Djibouti Egypt Equatorial Guinea Eritrea Ethiopia Gabon The Gambia Ghana Guinea Guinea-Bissau Ivory Coast (Côte d'Ivoire) Kenya Lesotho Liberia Libya Madagascar Malawi Mali Mauritania Mauritius Morocco Mozambique Namibia Niger Nigeria Rwanda São Tomé and Príncipe Senegal Seychelles Sierra Leone Somalia South Africa South Sudan Sudan Swaziland Tanzania Togo Tunisia Uganda Zambia Zimbabwe States with limited recognition Sahrawi Arab Democratic Republic Somaliland Dependencies and other territories Canary Islands / Ceuta / Melilla / Plazas de soberanía (Spain) Madeira (Portugal) Mayotte / Réunion (France) Saint Helena / Ascension Island / Tristan da Cunha (United Kingdom) Western Sahara v t e Telecommunications in Asia Sovereign states Afghanistan Armenia Azerbaijan Bahrain Bangladesh Bhutan Brunei Burma (Myanmar) Cambodia China Cyprus East Timor (Timor-Leste) Egypt Georgia India Indonesia Iran Iraq Israel Japan Jordan Kazakhstan North Korea South Korea Kuwait Kyrgyzstan Laos Lebanon Malaysia Maldives Mongolia Nepal Oman Pakistan Philippines Qatar Russia Saudi Arabia Singapore Sri Lanka Syria Tajikistan Thailand Turkey Turkmenistan United Arab Emirates Uzbekistan Vietnam Yemen States with limited recognition Abkhazia Nagorno-Karabakh Northern Cyprus Palestine South Ossetia Taiwan Other dependent territories British Indian Ocean Territory Christmas Island Cocos (Keeling) Islands Hong Kong Macau v t e Telecommunications in Europe Sovereign states Albania Andorra Armenia Austria Azerbaijan Belarus Belgium Bosnia and Herzegovina Bulgaria Croatia Cyprus Czech Republic Denmark Estonia Finland France Georgia Germany Greece Hungary Iceland Ireland Italy Kazakhstan Latvia Liechtenstein Lithuania Luxembourg Macedonia Malta Moldova Monaco Montenegro Netherlands Norway Poland Portugal Romania Russia San Marino Serbia Slovakia Slovenia Spain Sweden Switzerland Turkey Ukraine United Kingdom States with limited recognition Abkhazia Kosovo Nagorno-Karabakh Northern Cyprus South Ossetia Transnistria Dependencies and other territories Åland Faroe Islands Gibraltar Guernsey Jersey Isle of Man Svalbard Other entities European Union v t e Telecommunications in North America Sovereign states Antigua and Barbuda Bahamas Barbados Belize Canada Costa Rica Cuba Dominica Dominican Republic El Salvador Grenada Guatemala Haiti Honduras Jamaica Mexico Nicaragua Panama Saint Kitts and Nevis Saint Lucia Saint Vincent and the Grenadines Trinidad and Tobago United States Dependencies and other territories Anguilla Aruba Bermuda Bonaire British Virgin Islands Cayman Islands Curaçao Greenland Guadeloupe Martinique Montserrat Navassa Island Puerto Rico Saint Barthélemy Saint Martin Saint Pierre and Miquelon Saba Sint Eustatius Sint Maarten Turks and Caicos Islands United States Virgin Islands v t e Telecommunications in Oceania Sovereign states Australia Cook Islands Fiji Kiribati Marshall Islands Federated States of Micronesia Nauru New Zealand Niue Palau Papua New Guinea Samoa Solomon Islands Tonga Tuvalu Vanuatu Dependencies and other territories American Samoa Christmas Island Cocos (Keeling) Islands Easter Island French Polynesia Guam Hawaii New Caledonia Norfolk Island Northern Mariana Islands Pitcairn Islands Tokelau Wallis and Futuna v t e Telecommunications in South America Sovereign states Argentina Bolivia Brazil Chile Colombia Ecuador Guyana Paraguay Peru Suriname Uruguay Venezuela Dependencies and other territories Falkland Islands French Guiana South Georgia and the South Sandwich Islands