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| {{Redirect|VHF}}
| | Today, it's known by everyone that the prices of these products are getting on increasing. Here is the big reason on account of which existing standard of many people are suprisingly low. Several times persons feel it challenging to get their favorite things on account of not enough financing.<br><br>But, every dilemma has some answer as well as the same term applies around the difficulty that's being discussed. One of many many outstanding techniques for getting rid of this issue is always to avail discount discount voucher codes. These would be the codes that are the online version of the discount voucher that individuals usually observe within our daily newspapers. By providing these deals to the shopkeepers, you may get good incentives around the solution that you simply wish to have. Once you come to online shopping, the aforesaid discount codes achieve the identical goal. With the aid of the codes you get handsome abatement on the products online websites. Nevertheless, the strategy of applying these codes is indeed different from that of vouchers. Nevertheless, these are very simple to use. You simply must enter the code within the package as possible discover on the holder site of the buying website. Subsequently some total may routinely be noticed from your unique number of the merchandise.<br><br>These may be benefited from a number of websites. There are always a large numbers of websites that are especially made for offering such advantageous coupons. Apart, some retailer and affiliate websites will also be serving the same objective, nonetheless purchase and buy of these products can be done on these sites. If you're ignorant about these sites that are providing the codes subsequently it is quite simple to search them. Search engines like google enable a great deal to get the information regarding such websites. On searching in regards to the voucher codes you will get a long list of websites which present these codes. These codes are often given by the marketers for raising their consumers.<br><br>If you achieve such website which will be offering these codes, you then discover several categories of these vouchers. These categories may include, textbooks, audio, items, flowers etc. When you choose some of these categories, you obtain the deals on the same. You're able to select these according to your needs. Around the other-hand, on a number of the affiliate websites you will get other establishments which improve your knowledge about these codes. These websites facilitate the people so as to add their websites in addition to reviews. Using the support of this, you'll be able to present together with take the steering. If you have the noise information about the vouchers then you can increase your write ups to these sites. On the other-hand, you are able to consider the impartial information by studying the viewpoints of other consumers. Aside, many additional sites supply the posts around the discount codes by which you can consider the detailed info.<br><br>There's little doubt while in the proven fact that these discount voucher codes end up being very helpful for your people in addition to marketers. These deals on a single side enhance the existing standard of the people by reducing the costs of the products, around the other hand they boost the customer foot of the retailers and makers. For more infos visit [http://yoparo.org/content/coupons-and-voucher-codes-employs learn more]. |
| {{MWband
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| | freq = 30 to 300 [[megahertz|MHz]]
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| | wave = 10 to 1 m
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| | bands =
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| }}
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| [[Image:Antenna.jpg|thumb|VHF [[television antenna]]s used for [[broadcast television]] reception. These six antennas are a type known as a [[Yagi-Uda antenna|Yagi antenna]], which is widely used at VHF frequencies]]
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| '''Very high frequency''' ('''VHF''') is the [[International Telecommunications Union|ITU]]-designated range <ref name="ITU Nomenclature">{{cite web|title=Rec. ITU-R V.431-7, Nomenclature of the frequency and wavelength bands used in telecommunications|url=http://www.itu.int/dms_pubrec/itu-r/rec/v/R-REC-V.431-7-200005-I!!PDF-E.pdf|publisher=ITU|accessdate=20 February 2013}}</ref> of [[radio frequency]] [[electromagnetic wave]]s from {{nowrap|30 [[Megahertz|MHz]]}} to {{nowrap|300 [[Megahertz|MHz]]}}, with corresponding wavelengths of one to ten meters.
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| Frequencies immediately below VHF are denoted [[high frequency]] (HF), and the next higher frequencies are known as [[ultra high frequency]] (UHF).
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| 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 modem]]s, [[amateur radio]], and [[marine VHF radio|marine communications]]. [[Air traffic control]] communications and air navigation systems (e.g. [[VHF omnidirectional range|VOR]], [[Distance measuring equipment|DME]] & [[Instrument landing system|ILS]]) work at distances of 100 kilometres or more to aircraft at cruising altitude.
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| ==Propagation characteristics==
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| VHF [[Radio propagation|propagation]] characteristics are ideal for short-distance terrestrial communication, with a range generally somewhat farther than [[line-of-sight propagation|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
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| ==Line-of-sight calculation==
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| 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 propagation|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.
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| An approximation to calculate the line-of-sight horizon distance (on Earth) is:
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| *distance in nautical miles = <math>\sqrt{1.5 \times A_f}</math> where <math>A_f</math> is the height of the antenna in feet {{fact|date=June 2012}}
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| *distance in kilometres = <math>\sqrt{12.746 \times A_m}</math> where <math>A_m</math> is the height of the antenna in metres. {{fact|date=June 2012}}
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| 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.
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| In engineered communications systems, more complex calculations are required to assess the probable coverage area of a proposed transmitter station.{{Citation needed|date=June 2009}}
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| The accuracy of these calculations for [[digital television|digital TV]] signals is being debated.<ref name=grotticelli>{{cite news|url=http://broadcastengineering.com/news/dtv-transition-not-smooth-markets-0622/ |title=DTV Transition Not So Smooth in Some Markets |last=Grotticelli |first=Michael |date=2009-06-22|work=Broadcast Engineering |accessdate=2009-06-24}}</ref>
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| ==Antennas==
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| 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 [[transceiver]]s and [[walkie talkie]]s. Fixed station antennas are usually based on the [[dipole antenna|dipole]], while portable radios usually use [[whip antenna|whips]] or [[rubber ducky antenna]]s. The [[Yagi-Uda antenna|Yagi antenna]] is the most widely used as a high gain or "beam" antenna. [[Helical antenna|Helical]] and [[turnstile antenna]]s are used for [[satellite communication]] since they employ [[circular polarization]]. For even higher gain, multiple Yagis or helicals can be mounted together as an [[reflective array antenna|array antennas]]. Television and FM broadcasting stations use collinear arrays of specialized dipole antennas such as [[batwing antenna]]s.
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| ==Universal use==
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| Certain subparts of the VHF band have the same use around the world. Some national uses are detailed below.
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| *108–118 MHz: Air navigation beacons [[VHF omnidirectional range|VOR]] and [[Instrument Landing System]] localiser.
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| *118–137 MHz: [[Airband]] for [[air traffic control]], [[Amplitude modulation|AM]], 121.5 MHz is emergency frequency
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| *144–146 MHz: [[Amateur radio]]. In some countries 144–148 MHz.
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| ==By country==
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| [[File:VHF Usage.svg|thumb|500px|center|A plan showing VHF use in [[terrestrial television|television]], [[FM radio]], [[amateur radio]], [[marine radio]] and [[airband|aviation]].]]
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| {{clear}}
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| ===Australia===
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| 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.
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| 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.
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| 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 Television|NBN-3]] [[Newcastle, New South Wales|Newcastle]], [[WIN (TV station)|WIN-4]] [[Wollongong, New South Wales|Wollongong]] and [[Australian Broadcasting Corporation|ABC]] [[Newcastle, New South Wales|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 [[Ultra high frequency|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.
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| Two new VHF frequencies, 9A and 12, have since been made available and are being used primarily for digital services (e.g. [[Australian Broadcasting Corporation|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 Australia|digital radio]] in those cities are broadcast on DAB frequencies blocks 9A, 9B and 9C.
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| Refer to [[Australasian television frequencies]] for more information.
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| ===New Zealand===
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| *44–51, 54–68 MHz: [[Band I]] Television (channels 1–3)
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| *87.5–108 MHz: [[Band II]] Radio
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| *174–230 MHz: [[Band III]] Television (channels 4–11)
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| 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 [[Ultra high frequency|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 (New Zealand)|TV3]] and [[FOUR (New Zealand TV channel)|FOUR]]), is unavailable in some smaller towns.
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| However, by the end of 2013, there will be no television channels broadcasting on the VHF bands.<ref>{{cite web|first=Ministry for Culture and Heritage|title=Going Digital - When is my area going digital?|url=http://www.goingdigital.co.nz/making-the-switch/coverage-areas-2/coverage-areas.html|work=goingdigital.co.nz|publisher=Ministry for Culture and Heritage|accessdate=20 October 2011}}</ref>
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| Refer to [[Australasian television frequencies]] for more information.
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| ===United Kingdom===
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| 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).
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| British colour television was broadcast on [[Ultra high frequency|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 [[BBC Two|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.
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| Unusually, the UK has an [[amateur radio]] allocation at [[4 metres]], 70-70.5 MHz.
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| ===United States and Canada===
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| 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]].
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| The general services in the VHF band are:
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| *7-1001 MHz: [[North American television frequencies|Cable TV]]
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| *30–46 MHz: Licensed 2-way land mobile communication.<ref>The 42 MHz Segment is still currently used by the [[California Highway Patrol]], [[New Jersey State Police]], Tennessee Highway Patrol and other state law enforcement agencies.</ref>
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| *30–88 MHz: Military VHF-[[frequency modulation|FM]], including [[SINCGARS]]
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| *43–50 MHz: [[Cordless telephone]]s, 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.
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| *50–54 MHz: [[Amateur radio]] [[6-meter band|6 meters]] band
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| *54-72 and 76-88 MHz [[television|TV]] channels 2 through 6 (VHF-Lo), known as "Band I" internationally; some DTV stations will appear here. See [[North American broadcast television frequencies]]
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| *72–76 MHz: Radio controlled models, industrial remote control, and other devices. [[Radio-controlled aircraft|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.
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| *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)
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| *108–118 MHz: Air navigation beacons [[VHF omnidirectional range|VOR]]
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| *118–137 MHz: [[Airband]] for [[air traffic control]], [[Amplitude modulation|AM]], 121.5 MHz is an emergency frequency
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| *137-138 Space research, space operations, meteorological satellite <ref>Industry Canada, ''Canadian Table of Frequency Allocations 9 kHz - 275 GHz, 2005 Edition (revised February 2007)'' pg. 29</ref>
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| *138–144 MHz: Land mobile, auxiliary civil services, satellite, space research, and other miscellaneous services
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| *144–148 MHz: [[Amateur radio]] [[2-meter band|2 Meters]] band
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| *148-150 MHz: Land mobile, fixed, satellite
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| *150–156 MHz: "VHF [[business band]]," public safety, the unlicensed [[Multi-Use Radio Service]] (MURS), and other 2-way land mobile, FM
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| *156–158 MHz [[Marine VHF radio|VHF Marine Radio]]; narrow band FM, 156.8 MHz (Channel 16) is the maritime emergency and contact frequency.
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| * 159.81-161.565 MHz Railways <ref>The 160 and 161 areas are [[Association of American Railroads|AAR]] 99 channel [[railroad]] radios issued to the railroad (Sample, AAR 21 is 160.425 and that is issued to [[Tennessee Valley Railroad Museum|TVRM]] and other railroads that want AAR 21).</ref> 159.81-160.2 are railroads in Canada only and is used by trucking companies in the U.S.
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| *160.6-162 Wireless microphones and TV/FM broadcast remote pickup
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| *162.40–162.55: [[Weather radio|NOAA Weather Stations]], narrowband FM
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| *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.
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| *174–216 MHz: professional wireless microphones (low power, certain exact frequencies only)
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| *216–222 MHz: land mobile, fixed, maritime mobile,<ref>Canadian table pg. 30</ref>
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| *222–225 MHz: [[1.25-meter band|1.25 meters]] (US) (Canada 219-220, 222-225 MHz) [[amateur radio]]
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| *225 MHz and above: Military aircraft radio, 243 MHz is an emergency frequency (225–400 MHz) AM, including [[HAVE QUICK]], dGPS RTCM-104
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| ====VHF television====
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| The U.S. [[Federal Communications Commission|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.<ref>William Boddy, ''Fifties Television: The Industry and Its Critics'', University of Illinois Press, 1992, ISBN 978-0-252-06299-5</ref>
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| 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 ''[[Digital television#Effect on existing analog technology|Effect on existing analog technology]] for dates in other countries.
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| ====87.5-87.9 MHz====
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| '''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 [[Very High Frequency|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.
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| 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]].
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| ==Unlicensed operation==
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| 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 [[Compact Disk|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.<ref>{{cite web|url=http://media.ofcom.org.uk/2006/11/23/change-to-the-law-to-allow-the-use-of-low-power-fm-transmitters-for-mp3-players/ |title=Ofcom | Change to the law to allow the use of low power FM transmitters for MP3 players |publisher=Media.ofcom.org.uk |date= |accessdate=2012-10-02}}</ref>
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| ==See also==
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| *[[Marine VHF radio]]
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| *[[List of oldest radio stations]]
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| *[[Apex (radio band)]]
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| *[[FM broadcast band]]
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| *[[Moving image formats]]
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| *[[Polar mesosphere summer echoes]]
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| *[[Television channel frequencies]]
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| *[[Knife-edge effect]]
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| *[[Instrument Landing System]]
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| *[[VHF omnidirectional range]]
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| ==References==
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| {{Reflist}}
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| {{TVRband}}
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| {{Radio_spectrum}}
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| {{EMSpectrum}}
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| {{Telecommunications}}
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| {{Analogue TV transmitter topics}}
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| {{Audio broadcasting}}
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| {{DEFAULTSORT:Very High Frequency}}
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| [[Category:Radio spectrum]]
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| [[Category:Television terminology]]
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