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very high frequency (VHF)
Cycles per second: 30 MHz to 300 MHz

Wavelength: 10m to 1 m metre or meter, see meter (disambiguation) A metre or meter[1] (symbol: m) is a unit of length and the current base unit of length in the International System of Units (SI). ...

VHF frequencies' 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 radio and thus transmissions are restricted to the local area (and don't interfere with transmissions thousands of kilometres away). VHF 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.

Two unusual propagation conditions can allow much farther range than normal. The first, tropospheric ducting, can occur in front of and parallel to an advancing cold weather front, especially if there is a marked difference in humidities between the cold and warm air masses. A duct can form approximately 150 miles (240 km.) in advance of the cold front, much like a ventilation duct in a building, and VHF radio frequencies can travel along inside the duct, bending or refracting, for hundreds of miles. For example, a 50 watt Amateur FM transmitter at 146 MHz can talk from Chicago, Illinois, to Joplin, Missouri, directly, and to Austin, Texas, through a repeater. In a July 2006 incident, a Weatheradio station in north central Wisconsin was blocking out local stations in west central Michigan, quite far out of its normal range. The second type, much more rare, is called Sporadic-E, referring to the E-layer of the ionosphere. A sunspot eruption can pelt the Earth's upper atmosphere with charged particles, which may allow the formation of an ionized "patch" dense enough to reflect back VHF frequencies the same way HF frequencies are usually reflected (skywave). For example, TV channel 2 (54–60 MHz) from Midland, Texas was seen in Chicagoland, pushing out Chicago's own TV channel 2. These patches may last for seconds, or extend into hours. FM stations from Miami, Florida; New Orleans, Louisiana; Houston, Texas and even Mexico were heard for hours in central Illinois during one such event. Flag Seal Nickname: The Windy City Motto: Urbs In Horto (Latin: City in a Garden), I Will Location Location in Chicagoland and northern Illinois Coordinates , Government Country State Counties United States Illinois Cook, DuPage Mayor Richard M. Daley (D) Geographical characteristics Area     City 606. ... Main Street in Joplin in 2005 Joplin is a city located in parts of southern Jasper County and northern Newton County in the southwestern corner of Missouri. ... Flag Seal Nickname: Live Music Capital of the World Location Location in the state of Texas Coordinates: Government County Travis County Mayor Will Wynn Geographical characteristics Area 669. ... It has been suggested that this article or section be merged with Ionosphere. ... Sand storm that passed over Midland, Texas, February 20, 1894 at 6:00 p. ... Chicagoland is an informal name for the Chicago metropolitan area, used by local residents, businesses, governments, and planning agencies. ... Flag Seal Nickname: The Windy City Motto: Urbs In Horto (Latin: City in a Garden), I Will Location Location in Chicagoland and northern Illinois Coordinates , Government Country State Counties United States Illinois Cook, DuPage Mayor Richard M. Daley (D) Geographical characteristics Area     City 606. ... Nickname: The Magic City, Location in Miami-Dade County and the state of Florida. ... New Orleans is the largest city in the state of Louisiana, United States of America. ... Houston redirects here. ... Official language(s) English Capital Springfield Largest city Chicago Area  Ranked 25th  - Total 57,918 sq mi (149,998 kmÂ²)  - Width 210 miles (340 km)  - Length 390 miles (629 km)  - % water 4. ...

It was also easier to construct efficient transmitters, receivers, and antennas for it in the earlier days of radio, as compared to UHF. 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). Digital television (DTV) is a telecommunication system for broadcasting and receiving moving pictures and sound by means of digital signals, in contrast to analog signals in analog (traditional) TV. It uses digital modulation data, which is digitally compressed and requires decoding by a specially designed television set or a standard... 2008 (MMVIII) will be a leap year starting on Tuesday of the Gregorian calendar. ...

## Line of Sight Formula GA_googleFillSlot("encyclopedia_square");

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 line-of-sight phenomenon. Radio signals, like all electromagnetic radiation, usually travel in straight lines. ...

An approximation to calculate the line-of-sight horizon distance is:

• distance in miles = $sqrt{1.5 times A_f}$ where Af is the height of the antenna in feet
• distance in kilometres = $sqrt{12.7 times A_m}$ where Am is the height of the antenna in metres

## Australia

The VHF TV band in Australia was originally allocated channels 1 to 10 - with the 2, 7 and 9 frequencies assigned for the initial services in Sydney and Melbourne, and later the same frequencies would be assigned in Brisbane, Adelaide and Perth. Other capital cities and regional areas would utilise a combination of these and other frequencies as available.

By the early 1960s it was apparent that the 10-channel spectrum was not going to be sufficient 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 would require adjustment to enable tuning to the new frequencies.

Two new VHF frequencies, 9A and 12, have since been made available and are being utilised primarily for digital services (eg. ABC in capital cities) but also for some new analogue services in regional areas. The Australian Broadcasting Corporation (ABC) [1] is Australias national non-commercial public broadcaster. ...

## 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 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. This article is about the radio frequency. ...

## United Kingdom

Unusually, the UK has an amateur radio allocation at 4 metres, 70-70.5 MHz. Amateur radio, often called ham radio, is a hobby and public service enjoyed by about 3 million people[1] throughout the world. ... // Summary 4 metres is an Amateur Radio frequency band in the lower Very High Frequency spectrum. ...

## United States

The general services in the VHF band are:

• 30–46 MHz: Licensed 2-way land mobile communication
• 30–88 MHz: Military VHF-FM, including SINCGARS
• 43–50 MHz: Cordless telephones, "49 MHz" FM walkie-talkies, and mixed 2-way mobile communication
• 50–54 MHz: Amateur radio 6 meter band
• 54–72 MHz: TV channels 2-4
• 72–74 MHz: Remote Control devices
• 74–80 MHz: TV channel 5
• 81.5–87.5 MHz: TV channel 6
• 108–118 MHz: Air navigation beacons VOR
• 118–132 MHz: Airband for Air Traffic Control, AM, 121.5 MHz is emergency frequency
• 132–144 MHz: Auxiliary civil services, satellite, space research, and other miscellaneous services
• 144–148 MHz: Amateur band 2 Meters
• 148–174 MHz: "VHF Business band," the unlicensed Multi-Use Radio Service (MURS), and other 2-way land mobile, FM
• 156–174 MHz VHF Marine Radio; narrow band FM, 156.8 MHz (Channel 16) is the maritime emergency and contact frequency
• 162.40–162.55: NOAA Weather Stations, narrowband FM
• 174–216 MHz: TV channels 7 through 13, and professional wireless microphones (low power, certain exact frequencies only)
• 216–222 MHz: reserved for future use
• 222–225 MHz: Amateur "1¼ Meter" band (really closer to 1.33M)
• above 225 MHz: Federal services, notably military aircraft radio (225–400 MHz) AM, including HAVE QUICK, dGPS RTCM-104

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 microbroadcasting and sending output from CD or digital media players to radios without auxiliary-in jacks, though this is illegal in some other countries, most notably the United Kingdom. CD redirects here; see Cd for other meanings of CD. Image of a compact disc (pencil included for scale) A compact disc (or CD) is an optical disc used to store digital data, originally developed for storing digital audio. ...

## 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 the United States, however, this bandwidth is allocated to VHF channel 6 (81.5-87.5MHz). The audio for TV channel 6 is broadcast at 87.25 MHz. FM radio is a broadcast technology invented by Edwin Howard Armstrong that uses frequency modulation to provide high-fidelity sound over broadcast radio. ... Very high frequency (VHF) is the radio frequency range from 30 MHz (wavelength 10 m) to 300 MHz (wavelength 1 m). ...

87.9 MHz is normally is off-limits 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. Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... Mountain View is a city in Santa Clara County, in the U.S. state of California, USA. The city gets its name from the views of the Santa Cruz Mountains. ... Sun Valley is a census-designated place located in Washoe County, Nevada. ...

 Radio spectrum ELF SLF ULF VLF LF MF HF VHF UHF SHF EHF 3 Hz 30 Hz 300 Hz 3 kHz 30 kHz 300 kHz 3 MHz 30 MHz 300 MHz 3 GHz 30 GHz 30 Hz 300 Hz 3 kHz 30 kHz 300 kHz 3 MHz 30 MHz 300 MHz 3 GHz 30 GHz 300 GHz

Visible (optical) spectrum: The Electromagnetic Spectrum (Sorted by wavelength, short to long) Gamma ray | X-ray | Ultraviolet | Visible spectrum | Infrared | Terahertz radiation | Microwave | Radio waves Violet | Blue | Green | Yellow | Orange | Red W band | V band | K band: Ka band, Ku band | X band | C band | S band | L band EHF | SHF | UHF | VHF | HF | MF | LF | VLF | ULF | SLF | ELF Microwave | Shortwave | Mediumwave | Longwave

## External articles

• Tomislav Stimac, "Definition of frequency bands (VLF, ELF... etc.)". IK1QFK Home Page (vlf.it).

Results from FactBites:

 Very high frequency - Wikipedia, the free encyclopedia (1481 words) Common uses for VHF are FM radio broadcast at 88–108 MHz and television broadcast (together with UHF). VHF range is a function of transmitter power, receiver sensitivity, and the distance to the horizon, since VHF signals propagate under normal conditions as a line-of-sight phenomenon. The VHF TV band in Australia was originally allocated channels 1 to 10 - with the 2, 7 and 9 frequencies assigned for the initial services in Sydney and Melbourne, and later the same frequencies would be assigned in Brisbane, Adelaide and Perth.
More results at FactBites »

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