TV-FM DX
Encyclopedia
TV DX and FM DX is the active search for distant radio
or television station
s received during unusual atmospheric conditions. The term DX
is an old telegraphic
term meaning "long distance."
VHF
/UHF
television and radio signals are normally limited to a maximum "deep fringe" reception service area of approximately 40–100 mi (64.4–160.9 km) in areas where the broadcast spectrum is congested, and about 50 percent farther in the absence of interference. However, providing favourable atmospheric conditions are present, television and radio signals sometimes can be received hundreds or even thousands of miles outside their intended coverage area. These signals are often received using a large outdoor antenna
system connected to a sensitive TV or FM tuner
and/or receiver
.
While only a limited number of local stations can normally be received at satisfactory signal strengths in any given area, tuning into other channels may reveal weaker signals from adjacent areas. More consistently strong signals, especially those accentuated by unusual atmospheric conditions, can be achieved by improving the antenna system
. The development of interest in TV-FM DX as a hobby
can arise after more distant signals are either intentionally or accidentally discovered, leading to a serious interest in improving the listener's antenna and receiving installation for the purpose of actively seeking long-range television and radio reception. The TV-FM DX hobby is somewhat similar to other radio/electronic related hobbies such as amateur radio
, Medium Wave DX
, or short-wave radio, and organisations such as the Worldwide TV-FM DX Association have developed to coordinate and foster the further study and enjoyment of VHF/UHF television and FM broadcast DX.
, London
405-line
BBC
channel B1 TV service
in 1936, it soon became apparent that television reception was also possible well outside the original intended service area.
For example, in February 1938, engineers at the RCA
Research Station, Riverhead, Long Island, accidentally received a 3,000-mile (4,800 km) transatlantic
F2 reception of the London 45.0 MHz, 405-line channel B1 TV service.
The flickering black-and-white footage, (characteristic of F2 propagation) included Jasmine Bligh
, one of the original BBC announcers, and a brief shot of Elizabeth Cowell
, who also shared announcing duties with Jasmine, an excerpt from an unknown period costume drama and the BBC's station identification logo
transmitted at the beginning and end of the day's programmes.
This reception was recorded
on 16 mm movie
film
, and is now considered to be the only surviving example of pre-war, live British television.
The BBC temporarily ceased transmissions on September 1, 1939 as World War II
began. After the BBC channel B1 television service recommenced in 1946, distant reception reports were received from various parts of the world, including Italy
, South Africa
, India
, the Middle East
, North America
and the Caribbean
.
In May 1940, the Federal Communications Commission
(FCC), a U.S. government agency, formally allocated the 42 – 50 MHz band for FM radio broadcasting. It was soon apparent that distant FM signals from up to 1400 miles (2,253.1 km) distance would often interfere with local stations during the summer months.
Because the 42 – 50 MHz FM signals were originally intended to only cover a relatively confined service area, the sporadic long-distance signal propagation was seen as a nuisance, especially by station management.
In February 1942, the first known published long-distance FM broadcast station reception report was reported by FM magazine. The report provided details of 45.1 MHz W51C Chicago, Illinois, received in Monterrey
, Mexico
: "Zenith Radio Corporation, operating W51C, has received a letter from a listener in Monterey, Mexico, telling of daily reception of this station between 3:00 P.M. and 6:00 P.M. This is the greatest distance, 1,100 miles, from which consistent reception of the 50 [kW] transmitter has been reported."
In June 1945, the FCC decided that FM would have to move from the established 42 – 50 MHz pre-war band to a new band at 88 – 108 MHz. According to 1945 and 1946 FCC documents, the three major factors which the commission considered in its decision to place FM in the 88 – 108 MHz band were sporadic E co-channel interference, F2 layer interference, and extent of coverage.
During the 1950s to early 1960s, long-distance television reports started to circulate via popular U.S. electronics hobbyist periodical
s such as DXing Horizons, Popular Electronics
, Television Horizons, Radio Horizons, and Radio-Electronics
. In January 1960, the TV DX interest was further promoted via Robert B. Cooper's regular DXing Horizons column.
In 1957, the world record for TV DX was extended to 10800 miles (17,380.9 km) with the reception of Britain's BBC channel 1 in various parts of Australia
. Most notably, George Palmer in Melbourne, Victoria, received viewable pictures and audio of a news program from the BBC London channel B1 station. This BBC F2 reception was recorded on movie film.
During the early 1960s, the U.K.
magazine Practical Television
first published a regular TV DX column edited by Charles Rafarel. By 1970, Rafarel's column had attracted considerable interest from TV DXers worldwide. After Rafarel's death in 1971, UK TV DXer Roger Bunney continued the monthly column, which continued to be published by Television Magazine. With the demise of Television Magazine in June 2008, Bunney's column finished after 36 years of publication. In addition to the monthly TV DX column, Bunney has also published several TV DX books, including Long Distance Television Reception (TV-DX) for the Enthusiast 1981 ISBN 0-900162-71-6, and A TV DXer's Handbook 1986 ISBN 0-85934-150-X.
that develop seasonally within the E region of the ionosphere
and reflect TV and FM frequencies, generally up to about 150 MHz. Recently however the first ever two way contacts were made by amateur radio operators on the 220 mHz amateur band via E-Skip. When frequencies reflect off multiple patches, it is referred to as multi-hop skip. E-skip allows radio wave
s to travel a thousand miles or even more beyond their intended area of reception. E-skip is unrelated to tropospheric ducting.
By means of short-wave radio it is possible to transmit signals to distant countries around the world. Such communication is dependent upon a number of reflecting layers in the ionosphere, high above earth's surface known as the E, F1 and F2 layers. The E layer region lies at an approximate distance of 65 miles (104.6 km) above earth's surface. Under normal conditions the E layer reflects short-wave signals (at night, when the D layer dissolves, Mediumwave
signals are reflected as well). Normally, VHF and UHF signals pass through the E and F layers into outer space. At certain times, however, intense patches of ionisation form in the E layer, a phenomenon known as Sporadic E. Incident VHF signals that strike these patches are reflected back to earth. During such conditions television and radio transmissions in band 1 (45 – 88 MHz), band 2 (88 – 108 MHz), and very occasionally band 3 (175 – 220 MHz), are capable of being reflected, allowing reception at considerable distances.
Although Sporadic E can occur at any time of the year, the most active period is during the summer months, from early May to August (Northern Hemisphere
), and early November to February (Southern Hemisphere
). A small peak of activity is also usually noted in mid-winter in the Northern Hemisphere.
The length of a single-hop E-skip path varies between approximately 450 and 1500 mi (724.2 and 2,414 km). At times, double-hop Sporadic E can propagate signals over a 1900 to 2900 mi (3,057.7 to 4,667.1 km) path. During periods of extremely widespread Es ionisation, multi-hop signals up to 60 MHz have been received out to 5000 miles (8,046.7 km).
Television and FM signals received via Sporadic E can be extremely strong and range in strength over a short period from just detectable to overloading. Although polarisation shift can occur, single-hop Sporadic E signals tend to remain in the original transmitted polarisation. Long single-hop (900–1500 mi (1,448.4–2,414 km)) Sporadic E television signals tend to be more stable and relatively free of multipath images. Shorter-skip (400–800 mi (643.7–1,287.5 km)) signals tend to be reflected from more than one part of the Sporadic E layer, resulting in multiple images and ghosting, with phase reversal
at times. Picture degradation and signal-strength attenuation increases with each subsequent Sporadic E hop.
Sporadic E usually affects the lower VHF
band I (TV channels 2 – 6) and band II (88 – 108 MHz FM broadcast band). The typical expected distances are about 600 to 1400 mi (965.6 to 2,253.1 km). However, under exceptional circumstances, a highly ionized Es cloud can propagate band I VHF signals down to approximately 350 miles (563.3 km). When short-skip Es reception occurs, i.e., under 500 miles (804.7 km) in band I, there is a greater possibility that the ionized Es cloud will be capable of reflecting a signal at a much higher frequency – i.e., a VHF band 3 channel – since a sharp reflection angle (short skip) favours low frequencies, a shallower reflection angle from the same ionized cloud will favour a higher frequency.
At polar latitudes, Sporadic E can accompany auroras and associated disturbed magnetic conditions and is called Auroral-E.
No conclusive theory has yet been formulated as to the origin of Sporadic E. Attempts to connect the incidence of Sporadic E with the eleven-year Sunspot cycle have provided tentative correlations. There seems to be a positive correlation between sunspot maximum and Es activity in Europe. Conversely, there seems to be a negative correlation between maximum sunspot activity and Es activity in Australasia
.
ial E-skip is a regular daytime occurrence over the equatorial regions and is common in the temperate latitudes in late spring, early summer and, to a lesser degree, in early winter. For receiving stations located within +/− 10 degrees of the geomagnetic equator, equatorial E-skip can be expected on most days throughout the year, peaking around midday local time.
on frequencies as high as 432 MHz. Reception of lower frequencies in the 30 – 70 MHz range are most common. If sunspot activity is sufficiently high, signals up to 108 MHz are also possible. Reception of TEP signals above 220 MHz is extremely rare. Transmitting and receiving stations should be nearly equidistant from the geomagnetic equator
.
The first large-scale VHF TEP communications occurred around 1957 – 58 during the peak of solar cycle 19. Around 1970, the peak of cycle 20, many TEP contacts were made between Australian and Japanese radio amateurs. With the rise of cycle 21 starting around 1977, amateur contacts were made between Greece
/Italy
and Southern Africa (both South Africa and Rhodesia
/Zimbabwe
), and between Central and South America by TEP.
There are two distinctly different types of TEP: afternoon TEP and evening TEP.
Evening TEP is quenched by moderate to severe geomagnetic disturbances. The occurrence of evening TEP is more heavily dependent on high solar activity than is the afternoon type.
During late September 2001, from 2000 to 2400 local time, VHF television and radio signals from Japan
and Korea up to 220 MHz were received via evening transequatorial propagation near Darwin, Australia.
Since 1953, radio amateurs have been experimenting with lunar communications by reflecting VHF and UHF signals off the moon
. Moonbounce
allows communication on earth between any two points that can observe the moon at a common time.
Since the moon's mean distance from earth is 239000 miles (384,632.3 km), path losses are very high. It follows that a typical 240 dB
total path loss places great demand on high-gain receiving antennas, high-power transmissions, and sensitive receiving systems. Even when all these factors are observed, the resulting signal level is often just above the noise.
Because of the low signal-to-noise ratio
, as with amateur-radio practice, EME signals can generally only be detected using narrow-band receiving systems. This means that the only aspect of the TV signal that could be detected is the field scan modulation (AM vision carrier). FM broadcast signals also feature wide frequency modulation, hence EME reception is generally not possible. There are no published records of VHF/UHF EME amateur radio contacts using FM.
For three nights in December 1978, astronomer
Dr. Woodruff T. Sullivan III
used the 305-metre Arecibo radio telescope
to observe the Moon at a variety of frequencies. This experiment demonstrated that the lunar surface is capable of reflecting terrestrial
band III (175 – 230 MHz) television signals back to earth. While not yet confirmed, FM broadcast EME reception may also be possible using the Arecibo dish antenna.
In 2002, physicist
Dr. Tony Mann demonstrated that a single high-gain UHF yagi antenna
, low noise masthead preamplifier, VHF/UHF synthesised communications receiver, and personal computer with FFT
spectrum analyser
software could be used to successfully detect extremely weak UHF television carriers via EME.
is most likely to occur during periods of high solar activity when there is a high probability of a large solar flare
. When such an eruption occurs, charged particles from the flare may spiral towards earth arriving about a day later. This may or may not cause an aurora: if the interstellar magnetic field has same polarity, the particles do not get coupled to the geomagnetic field efficiently. Besides sunspot-related active solar surface areas, there are other solar phenomena that produce particles causing auroras, such as re-occurring coronal holes spraying out intense solar wind
. These charged particles are affected and captured by the geomagentic field and the various radiation belts
surrounding earth. The aurora-producing relativistic electrons eventually precipitate towards earth's magnetic poles, resulting in an aurora which disrupts short-wave communications (SID) due to ionospheric/magnetic storms in the D, E, and F layers. Various visual effects are also seen in the sky towards the north – aptly called the Northern Lights
. The same effect occurs in the Southern Hemisphere, but the visual effects are towards the south. The auroral event starts by onset of geomagnetic storm, followed by number of sub-storms over the next day or so.
The aurora produces a reflecting sheet (or metric sized columns) which tends to lie in a vertical plane. The result of this vertical ionospheric "curtain" is reflection of signals well into the upper VHF band. The reflection is very aspect sensitive. Since the reflecting sheet lies towards the poles, it follows that reflected signals will arrive from that general direction. An active region or coronal hole may persist for some 27 days resulting in a second aurora when the Sun has rotated. There is a tendency for auroras to occur around the March/April, September/October equinox
periods, when the geomagnetic field is at right angle to Sun for efficient charged particle coupling. Signals propagated by aurora have a characteristic hum effect, which makes video and audio reception difficult. Video carriers, as heard on a communications receiver, no longer can be heard as a pure tone.
A typical radio aurora occurs in the afternoon, which produces strong and distorted signals for few hours. The local midnight sub-storming usually produces weaker signals, but with less distortion by Doppler from gyrating electrons.
Frequencies up to 200 MHz can be affected by auroral propagation.
scatter occurs when a signal bounces off a meteor's ionized trail.
When a meteor strikes earth's atmosphere, a cylindrical region of free electron
s is formed at the height of the E layer. This slender, ionized column is relatively long, and when first formed is sufficiently dense to reflect and scatter television and radio signals, generally observable from 25 MHz upwards through UHF TV, back to earth. Consequently an incident television or radio signal is capable of being reflected up to distances approaching that of conventional Sporadic E propagation, typically about 1500 km. A signal reflected by such meteor ionisation can vary in duration from fractions of a second up to several minutes for intensely ionized trails. The events are classified as overdense and underdense, depending on the electron line-density (related to used frequency) of the trail plasma. The signal from overdense trail has a longer signal decay associated with fading and is a physically a reflection from the ionized cylinder surface, while an underdense trail gives a signals of short duration, which rises fast and decays exponentially and is scatter from individual electrons inside the trail.
Frequencies in the range of 50 to 80 MHz have been found to be optimum for meteor scatter propagation. The 88 – 108 MHz FM broadcast band is also highly suited for meteor scatter experiments. During the major meteor showers, with extremely intense trails, band III 175 – 220 MHz signal reception can occur.
Ionized trails generally reflect lower frequencies for longer periods (and produce stronger signals) compared to higher frequencies. For example, an 8-second burst on 45.25 MHz may only cause a 4-second burst at 90.5 MHz.
The effect of a typical visually seen single meteor (of size 0.5 mm) shows up as a sudden "burst" of signal of short duration at a point not normally reached by the transmitter. The combined effect of several meteors impinging on earth's atmosphere, while perhaps too weak to provide long-term ionisation, is thought to contribute to the existence of the night-time E layer.
The optimum time for receiving RF reflections off sporadic meteors is the early morning period, when the velocity
of earth relative to the velocity of the particles is greatest which also increases the number of meteors occurring on the morning-side of the earth, but some sporadic meteor reflections can received at any time of the day, least in the early evening.
The annual major meteor showers are detailed below:
For observing meteor shower-related radio signals, the shower's radiant must be above the (propagation mid path) horizon. Otherwise no meteor of the shower can hit the atmosphere along the propagation path and no reflections from shower's meteor trails can be observed.
UHF TVRO reception is related in certain aspects. For example, reception of satellite signals requires sensitive receiving systems and large outdoor antenna systems. However, unlike terrestrial TV DX, satellite UHF TV reception is far easier to predict. The geosynchronous satellite at 22375 miles (36,009 km) height is a line of sight reception source. If the satellite is above the horizon, it can be generally received, if it is below the horizon, reception is not possible.
and digital television
can also be received, however there is much greater difficulty with reception of weak signals due to the cliff effect
, particularly with the ATSC
TV standard mandated in the U.S. For DVB-T
, hierarchical modulation
may allow a lower-definition signal to be received even if the details of the full signal cannot be decoded. A unique issue observed on analog TV at the end of the DTV transition in the United States
was that very distant analog stations were viewable in the hours after the permanent shutdown of local analog transmitters in June 2009. This was particularly pronounced because June is one of the strongest months for DX reception on VHF, and most digital stations were assigned to UHF.
Radio station
Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...
or television station
Television station
A television station is a business, organisation or other such as an amateur television operator that transmits content over terrestrial television. A television transmission can be by analog television signals or, more recently, by digital television. Broadcast television systems standards are...
s received during unusual atmospheric conditions. The term DX
DXing
DXing is the hobby of tuning in and identifying distant radio or television signals, or making two way radio contact with distant stations in amateur radio, citizens' band radio or other two way radio communications. Many DXers also attempt to receive written verifications of reception from the...
is an old telegraphic
Telegraphy
Telegraphy is the long-distance transmission of messages via some form of signalling technology. Telegraphy requires messages to be converted to a code which is known to both sender and receiver...
term meaning "long distance."
VHF
Very high frequency
Very high frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency...
/UHF
Ultra high frequency
Ultra-High Frequency designates the ITU Radio frequency range of electromagnetic waves between 300 MHz and 3 GHz , also known as the decimetre band or decimetre wave as the wavelengths range from one to ten decimetres...
television and radio signals are normally limited to a maximum "deep fringe" reception service area of approximately 40–100 mi (64.4–160.9 km) in areas where the broadcast spectrum is congested, and about 50 percent farther in the absence of interference. However, providing favourable atmospheric conditions are present, television and radio signals sometimes can be received hundreds or even thousands of miles outside their intended coverage area. These signals are often received using a large outdoor antenna
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
system connected to a sensitive TV or FM tuner
Tuner (radio)
A radio tuner is a subsystem that receives radio broadcasts and converts them into audio-frequency signals which can be fed into an amplifier driving a loudspeaker. FM tuner, AM tuner, Digital Audio Broadcasting DAB tuner, etc. are types of radio tuner dealing with transmissions using different...
and/or receiver
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
.
While only a limited number of local stations can normally be received at satisfactory signal strengths in any given area, tuning into other channels may reveal weaker signals from adjacent areas. More consistently strong signals, especially those accentuated by unusual atmospheric conditions, can be achieved by improving the antenna system
Television antenna
A television antenna, or TV aerial, is an antenna specifically designed for the reception of over the air broadcast television signals, which are transmitted at frequencies from about 41 to 250 MHz in the VHF band, and 470 to 960 MHz in the UHF band in different countries...
. The development of interest in TV-FM DX as a hobby
Hobby
A hobby is a regular activity or interest that is undertaken for pleasure, typically done during one's leisure time.- Etymology :A hobby horse is a wooden or wickerwork toy made to be ridden just like a real horse...
can arise after more distant signals are either intentionally or accidentally discovered, leading to a serious interest in improving the listener's antenna and receiving installation for the purpose of actively seeking long-range television and radio reception. The TV-FM DX hobby is somewhat similar to other radio/electronic related hobbies such as amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
, Medium Wave DX
MW DX
MW DX, short for mediumwave DXing, is the hobby of receiving the reception of distant mediumwave radio stations. MW DX is similar to TV and FM DX in that broadcast band stations are the reception targets...
, or short-wave radio, and organisations such as the Worldwide TV-FM DX Association have developed to coordinate and foster the further study and enjoyment of VHF/UHF television and FM broadcast DX.
History
After the introduction of the Alexandra PalaceAlexandra Palace
Alexandra Palace is a building in North London, England. It stands in Alexandra Park, in an area between Hornsey, Muswell Hill and Wood Green...
, London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
405-line
405-line
The 405-line monochrome analogue television broadcasting system was the first fully electronic television system to be used in regular broadcasting....
BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
channel B1 TV service
BBC One
BBC One is the flagship television channel of the British Broadcasting Corporation in the United Kingdom. It was launched on 2 November 1936 as the BBC Television Service, and was the world's first regular television service with a high level of image resolution...
in 1936, it soon became apparent that television reception was also possible well outside the original intended service area.
For example, in February 1938, engineers at the RCA
RCA
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
Research Station, Riverhead, Long Island, accidentally received a 3,000-mile (4,800 km) transatlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
F2 reception of the London 45.0 MHz, 405-line channel B1 TV service.
The flickering black-and-white footage, (characteristic of F2 propagation) included Jasmine Bligh
Jasmine Bligh
Jasmine Lydia Bligh was one of the first three BBC Television Service presenters in the 1930s, along with Leslie Mitchell and Elizabeth Cowell, providing continuity announcements and introducing programmes in-vision....
, one of the original BBC announcers, and a brief shot of Elizabeth Cowell
Elizabeth Cowell
Elizabeth Cowell was a British broadcaster.She was one of the first three BBC Television Service presenters, along with Jasmine Bligh and Leslie Mitchell. She began announcing when the Television Service started in 1936, and returned in 1946 after its nearly seven-year hiatus due to the Second...
, who also shared announcing duties with Jasmine, an excerpt from an unknown period costume drama and the BBC's station identification logo
Logo
A logo is a graphic mark or emblem commonly used by commercial enterprises, organizations and even individuals to aid and promote instant public recognition...
transmitted at the beginning and end of the day's programmes.
This reception was recorded
Kinescope
Kinescope , shortened to kine , also known as telerecording in Britain, is a recording of a television program made by filming the picture from a video monitor...
on 16 mm movie
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
film
Photographic film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...
, and is now considered to be the only surviving example of pre-war, live British television.
The BBC temporarily ceased transmissions on September 1, 1939 as World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
began. After the BBC channel B1 television service recommenced in 1946, distant reception reports were received from various parts of the world, including Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
, North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...
.
In May 1940, the Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
(FCC), a U.S. government agency, formally allocated the 42 – 50 MHz band for FM radio broadcasting. It was soon apparent that distant FM signals from up to 1400 miles (2,253.1 km) distance would often interfere with local stations during the summer months.
Because the 42 – 50 MHz FM signals were originally intended to only cover a relatively confined service area, the sporadic long-distance signal propagation was seen as a nuisance, especially by station management.
In February 1942, the first known published long-distance FM broadcast station reception report was reported by FM magazine. The report provided details of 45.1 MHz W51C Chicago, Illinois, received in Monterrey
Monterrey
Monterrey , is the capital city of the northeastern state of Nuevo León in the country of Mexico. The city is anchor to the third-largest metropolitan area in Mexico and is ranked as the ninth-largest city in the nation. Monterrey serves as a commercial center in the north of the country and is the...
, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
: "Zenith Radio Corporation, operating W51C, has received a letter from a listener in Monterey, Mexico, telling of daily reception of this station between 3:00 P.M. and 6:00 P.M. This is the greatest distance, 1,100 miles, from which consistent reception of the 50 [kW] transmitter has been reported."
In June 1945, the FCC decided that FM would have to move from the established 42 – 50 MHz pre-war band to a new band at 88 – 108 MHz. According to 1945 and 1946 FCC documents, the three major factors which the commission considered in its decision to place FM in the 88 – 108 MHz band were sporadic E co-channel interference, F2 layer interference, and extent of coverage.
During the 1950s to early 1960s, long-distance television reports started to circulate via popular U.S. electronics hobbyist periodical
Magazine
Magazines, periodicals, glossies or serials are publications, generally published on a regular schedule, containing a variety of articles. They are generally financed by advertising, by a purchase price, by pre-paid magazine subscriptions, or all three...
s such as DXing Horizons, Popular Electronics
Popular Electronics
Popular Electronics was an American magazine started by Ziff-Davis Publishing in October 1954 for electronics hobbyists and experimenters. It soon became the "World's Largest-Selling Electronics Magazine". The circulation was 240,151 in April 1957 and 400,000 by 1963. Ziff-Davis published Popular...
, Television Horizons, Radio Horizons, and Radio-Electronics
Radio-Electronics
Radio-Electronics was an American electronics magazine that was published under various titles from 1929 to 2003. Hugo Gernsback started it as Radio-Craft in July 1929. The title was changed to Radio-Electronics in October 1948 and again to Electronics Now in July 1992. In January 2000 it was...
. In January 1960, the TV DX interest was further promoted via Robert B. Cooper's regular DXing Horizons column.
In 1957, the world record for TV DX was extended to 10800 miles (17,380.9 km) with the reception of Britain's BBC channel 1 in various parts of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. Most notably, George Palmer in Melbourne, Victoria, received viewable pictures and audio of a news program from the BBC London channel B1 station. This BBC F2 reception was recorded on movie film.
During the early 1960s, the U.K.
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
magazine Practical Television
Practical Television
Practical Television, later known as Television and subsequently Television & Consumer Electronics, was a UK magazine for the electronics/TV servicing trade, enthusiasts, and the general public....
first published a regular TV DX column edited by Charles Rafarel. By 1970, Rafarel's column had attracted considerable interest from TV DXers worldwide. After Rafarel's death in 1971, UK TV DXer Roger Bunney continued the monthly column, which continued to be published by Television Magazine. With the demise of Television Magazine in June 2008, Bunney's column finished after 36 years of publication. In addition to the monthly TV DX column, Bunney has also published several TV DX books, including Long Distance Television Reception (TV-DX) for the Enthusiast 1981 ISBN 0-900162-71-6, and A TV DXer's Handbook 1986 ISBN 0-85934-150-X.
Sporadic E propagation (E-skip)
Sporadic E, also called E-skip, is the phenomenon of irregularly scattered patches of relatively dense ionizationIonization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
that develop seasonally within the E region of the ionosphere
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
and reflect TV and FM frequencies, generally up to about 150 MHz. Recently however the first ever two way contacts were made by amateur radio operators on the 220 mHz amateur band via E-Skip. When frequencies reflect off multiple patches, it is referred to as multi-hop skip. E-skip allows radio wave
Radio Wave
Radio Wave may refer to:*Radio frequency*Radio Wave 96.5, a radio station in Blackpool, UK...
s to travel a thousand miles or even more beyond their intended area of reception. E-skip is unrelated to tropospheric ducting.
By means of short-wave radio it is possible to transmit signals to distant countries around the world. Such communication is dependent upon a number of reflecting layers in the ionosphere, high above earth's surface known as the E, F1 and F2 layers. The E layer region lies at an approximate distance of 65 miles (104.6 km) above earth's surface. Under normal conditions the E layer reflects short-wave signals (at night, when the D layer dissolves, Mediumwave
Mediumwave
Medium wave is the part of the medium frequency radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz...
signals are reflected as well). Normally, VHF and UHF signals pass through the E and F layers into outer space. At certain times, however, intense patches of ionisation form in the E layer, a phenomenon known as Sporadic E. Incident VHF signals that strike these patches are reflected back to earth. During such conditions television and radio transmissions in band 1 (45 – 88 MHz), band 2 (88 – 108 MHz), and very occasionally band 3 (175 – 220 MHz), are capable of being reflected, allowing reception at considerable distances.
Although Sporadic E can occur at any time of the year, the most active period is during the summer months, from early May to August (Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...
), and early November to February (Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
). A small peak of activity is also usually noted in mid-winter in the Northern Hemisphere.
The length of a single-hop E-skip path varies between approximately 450 and 1500 mi (724.2 and 2,414 km). At times, double-hop Sporadic E can propagate signals over a 1900 to 2900 mi (3,057.7 to 4,667.1 km) path. During periods of extremely widespread Es ionisation, multi-hop signals up to 60 MHz have been received out to 5000 miles (8,046.7 km).
Television and FM signals received via Sporadic E can be extremely strong and range in strength over a short period from just detectable to overloading. Although polarisation shift can occur, single-hop Sporadic E signals tend to remain in the original transmitted polarisation. Long single-hop (900–1500 mi (1,448.4–2,414 km)) Sporadic E television signals tend to be more stable and relatively free of multipath images. Shorter-skip (400–800 mi (643.7–1,287.5 km)) signals tend to be reflected from more than one part of the Sporadic E layer, resulting in multiple images and ghosting, with phase reversal
Phase (waves)
Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...
at times. Picture degradation and signal-strength attenuation increases with each subsequent Sporadic E hop.
Sporadic E usually affects the lower VHF
Very high frequency
Very high frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency...
band I (TV channels 2 – 6) and band II (88 – 108 MHz FM broadcast band). The typical expected distances are about 600 to 1400 mi (965.6 to 2,253.1 km). However, under exceptional circumstances, a highly ionized Es cloud can propagate band I VHF signals down to approximately 350 miles (563.3 km). When short-skip Es reception occurs, i.e., under 500 miles (804.7 km) in band I, there is a greater possibility that the ionized Es cloud will be capable of reflecting a signal at a much higher frequency – i.e., a VHF band 3 channel – since a sharp reflection angle (short skip) favours low frequencies, a shallower reflection angle from the same ionized cloud will favour a higher frequency.
At polar latitudes, Sporadic E can accompany auroras and associated disturbed magnetic conditions and is called Auroral-E.
No conclusive theory has yet been formulated as to the origin of Sporadic E. Attempts to connect the incidence of Sporadic E with the eleven-year Sunspot cycle have provided tentative correlations. There seems to be a positive correlation between sunspot maximum and Es activity in Europe. Conversely, there seems to be a negative correlation between maximum sunspot activity and Es activity in Australasia
Australasia
Australasia is a region of Oceania comprising Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes...
.
Equatorial E-skip
EquatorEquator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
ial E-skip is a regular daytime occurrence over the equatorial regions and is common in the temperate latitudes in late spring, early summer and, to a lesser degree, in early winter. For receiving stations located within +/− 10 degrees of the geomagnetic equator, equatorial E-skip can be expected on most days throughout the year, peaking around midday local time.
Notable sporadic E DX receptions
- In 1939, there were some news reports of reception of an early ItalianItalyItaly , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
television service in EnglandEnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
about 900 miles (1,448.4 km) away. - The Medford Mail Tribune in Medford, OregonMedford, OregonMedford is a city in Jackson County, Oregon, United States. As of the 2010 US Census, the city had a total population of 74,907 and a metropolitan area population of 207,010, making the Medford MSA the 4th largest metro area in Oregon...
reported on June 1, 1953, that KGNC-TV, Channel 4 in Amarillo, and KFEL-TVKWGN-TVKWGN-TV, virtual channel 2 , is a television station in Denver, Colorado, owned by the Tribune Company and affiliated with the CW Television Network...
, Channel 2 from Denver had been received on the Trowbridge and Flynn Electric Company’s television set at their Court Street warehouse and, with a pre-amplifier, a New York station’s test pattern was reportedly picked up. - On August 2, 1957, the world record for high-band (channels 7 – 13) sporadic E television DX was extended to approximately 2300 miles (3,701.5 km) with the reception of the YVLV channel 9 relay from Maracaibo, Venezuela, by Bobby Grimes in Little Rock, ArkansasLittle Rock, ArkansasLittle Rock is the capital and the largest city of the U.S. state of Arkansas. The Metropolitan Statistical Area had a population of 699,757 people in the 2010 census...
. Two hours later, Bedford Brown of Hot Springs, ArkansasHot Springs, ArkansasHot Springs is the 10th most populous city in the U.S. state of Arkansas, the county seat of Garland County, and the principal city of the Hot Springs Metropolitan Statistical Area encompassing all of Garland County...
, also received the channel 9 station, along with multi-hop sporadic E reception from VenezuelaVenezuelaVenezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
on channels 2, 4 and 5. BrazilBrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
ian television on channel 2 and ArgentinaArgentinaArgentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
on channel 3 were also received via transequatorial propagation (TEP). - On June 30, 1975, Glenn HauserGlenn HauserGlenn Hauser is an internationally-known DXer and radio host from Enid, Oklahoma, United States. He produces and narrates the weekly 30-minute radio show "World Of Radio", heard on various non-commercial AM and FM radio stations throughout the U.S., plus worldwide on shortwave radio.Glenn Hauser...
of Enid, OklahomaEnid, OklahomaEnid is a city in Garfield County, Oklahoma, United States. In 2010, the population was 49,379, making it the ninth largest city in Oklahoma. It is the county seat of Garfield County. Enid was founded during the opening of the Cherokee Outlet in the Land Run of 1893, and is named after Enid, a...
, logged WJCT-TV 7, WFLA-TVWFLA-TVWFLA-TV, virtual channel 8, is the NBC-affiliated television station in Tampa/St. Petersburg, Florida. The station is the flagship station of its owner and operator, Media General. Its transmitter is located in Riverview, Hillsborough County, Florida. WFLA is the only station in the market to be...
8, WJHG-TVWJHG-TVWJHG-TV, channel 7 is the NBC affiliate for Panama City, Florida. Owned by Gray Television, its studios are located in Panama City Beach while its transmitter is located in Youngstown.-History:...
7, WFTV-TV 9, & WTVT-TV 13 during intense Sporadic E conditions. The distances were all around 1020–1090 mi (1,641.5–1,754.2 km). Bob Seybold also noted band III Sporadic E, Dunkirk, NY KOAM-TVKOAM-TVKOAM-TV is a television station in Pittsburg, Kansas broadcasting on channel 7 and affiliated with CBS. The station also serves Joplin, Missouri, along with the Four State Area region of Kansas, Oklahoma, Arkansas and Missouri. KOAM-TV transmits from Columbus, Kansas, and is the sister station to...
7 on June 16. - In June 1981, Rijn Muntjewerff (the NetherlandsNetherlandsThe Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
) received 55.25 MHz TV-2 Guaiba, Porto Alegre, Brazil, via a combination of sporadic E and afternoon TEP at a distance of 6320 miles (10,171 km). - On May 30, 2003, Girard Westerberg made the first known reception of digital television by sporadic E when he decoded the PSIPProgram and System Information ProtocolThe Program and System Information Protocol is the protocol used in the ATSC digital television system for carrying metadata about each channel in the broadcast MPEG transport stream of a TV station and for publishing information about television programs so that viewers can select what to watch...
ID of KOTA-DTKOTA-TVKOTA-TV, channel 3, is an ABC television affiliate based in Rapid City, South Dakota, USA. The station is owned by the Duhamel family of Rapid City...
(broadcasting on channel 2 in Rapid City, South DakotaRapid City, South DakotaRapid City is the second-largest city in the U.S. state of South Dakota, and the county seat of Pennington County. Named after Rapid Creek on which the city is established, it is set against the eastern slope of the Black Hills mountain range. The population was 67,956 as of the 2010 Census. Rapid...
) in Lexington, KentuckyLexington, KentuckyLexington is the second-largest city in Kentucky and the 63rd largest in the US. Known as the "Thoroughbred City" and the "Horse Capital of the World", it is located in the heart of Kentucky's Bluegrass region...
, 1062 miles (1,709.1 km) away. - On June 26, 2003, Paul Logan (LisnaskeaLisnaskeaLisnaskea is the second-biggest settlement in County Fermanagh, Northern Ireland. It had a population of 2,739 people in the 2001 Census. The town is built around the long main street, which bends at almost 90 degrees along its course.- History :...
, Northern Ireland) was the first DXer to receive transatlantic Sporadic E at frequencies above 88 MHz. Stations received included 88.5 MHz WHCF Bangor, MaineBangor, MaineBangor is a city in and the county seat of Penobscot County, Maine, United States, and the major commercial and cultural center for eastern and northern Maine...
(2732 miles (4,396.7 km)), and 97.5 MHz WFRY Watertown, New YorkWatertown (city), New YorkWatertown is a city in the state of New York and the county seat of Jefferson County. It is situated approximately south of the Thousand Islands. As of the 2010 census, it had a population of 27,023, an increase of 1.2% since 2000. The U.S...
(3040 miles (4,892.4 km)). David Hamilton from CumnockCumnockCumnock is a town in East Ayrshire, Scotland. The town sits at the confluence of the Glaisnock Water and the Lugar Water...
in AyrshireAyrshireAyrshire is a registration county, and former administrative county in south-west Scotland, United Kingdom, located on the shores of the Firth of Clyde. Its principal towns include Ayr, Kilmarnock and Irvine. The town of Troon on the coast has hosted the British Open Golf Championship twice in the...
, ScotlandScotlandScotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
received CBTB from Baie Verte, Newfoundland and LabradorBaie Verte, Newfoundland and LabradorBaie Verte is a town located on the northeast coast of the island portion of the Canadian province of Newfoundland and Labrador on the Baie Verte Peninsula.-Geography:...
, Canada on 97.1 MHz on this day also. - On June 26, 2003, several IrishIrelandIreland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
and BritishUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
DXers received television signals from across the Atlantic via double-hop Sporadic E (it was also achieved on June 7 - On July 20, 2003, Paul Logan, Lisnaskea, Northern Ireland achieved a second reception of CBAF Moncton, New Brunswick on 88.5 MHz at 02:15 local time.
- On May 12, 2004, Matthew C. Sittel of Bellevue, NebraskaBellevue, NebraskaBellevue is a city in Sarpy County, Nebraska, United States. The population was 50,137 at the 2010 census. Eight miles south of Omaha, Bellevue is part of the Omaha-Council Bluffs metropolitan area. Originally settled in the 1830s, It was the first state capitol. Bellevue was incorporated in...
received WKYC-DTWKYC-TVWKYC, virtual channel 3 , is an NBC-affiliated television station located in Cleveland, Ohio, owned by the Gannett Company. Its studio is located on the shores of Lake Erie, while its transmitter is located in Parma, Ohio....
(channel 2 in Cleveland, OhioCleveland, OhioCleveland is a city in the U.S. state of Ohio and is the county seat of Cuyahoga County, the most populous county in the state. The city is located in northeastern Ohio on the southern shore of Lake Erie, approximately west of the Pennsylvania border...
) via sporadic E at a distance of 740 miles (1,190.9 km). A partially decoded video frame was also obtained. - On May 26, 2004, Girard Westerberg decoded several perfect frames of digital TV video, again from KOTA-DT, along with a few other DXers in his area.
- On July 6, 2004, a spectacular intense high MUF Sporadic-E opening allowed David Pierce to receive KAKE-TVKAKE-TVKAKE, channel 10, is an ABC-affiliated television station based in Wichita, Kansas. The station is owned by Atlanta, Georgia-based Gray Television...
(channel 10, Wichita, KansasWichita, KansasWichita is the largest city in the U.S. state of Kansas.As of the 2010 census, the city population was 382,368. Located in south-central Kansas on the Arkansas River, Wichita is the county seat of Sedgwick County and the principal city of the Wichita metropolitan area...
) in Woodbridge, VirginiaWoodbridge, Virginia-Demographics:As of the census of 2000, there were 31,941 people, 10,687 households, and 7,769 families residing in the CDP. The population density was 3,047.8 people per square mile . There were 11,026 housing units at an average density of 1,052.1/sq mi...
, 1098 miles (1,767.1 km) away, and allowed Mike Bugaj to receive KATVKATVKATV, channel 7, is an ABC affiliated television station serving the Little Rock television market and central Arkansas. The station is owned by Allbritton Communications Company....
(channel 7, Little Rock, ArkansasLittle Rock, ArkansasLittle Rock is the capital and the largest city of the U.S. state of Arkansas. The Metropolitan Statistical Area had a population of 699,757 people in the 2010 census...
) in Enfield, ConnecticutEnfield, ConnecticutEnfield is a town located in Hartford County, Connecticut, United States. The population was 45,212 at the 2000 census. It sits on the border with Longmeadow, Massachusetts and East Longmeadow, Massachusetts to the north, Somers to the east, East Windsor and Ellington to the south, and the...
, 1176 miles (1,892.6 km) away. - On July 10, 2004, Matt Sittel achieved what was then the longest DTV reception, receiving KVBC-DT (channel 2, Las Vegas, NevadaLas Vegas, NevadaLas Vegas is the most populous city in the U.S. state of Nevada and is also the county seat of Clark County, Nevada. Las Vegas is an internationally renowned major resort city for gambling, shopping, and fine dining. The city bills itself as The Entertainment Capital of the World, and is famous...
) at a distance of 1088 miles (1,751 km) (note the NBC logo in the upper right corner of the picture). - On July 7, 2004, several UK TV DXers received channels A2, A3, A4 and A5 from Puerto RicoPuerto RicoPuerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
via multi-hop Sporadic E at distances of some 4,000+ miles (6,400+ km). - On several occasions in May 2005, Danny Oglethorpe of Shreveport, LouisianaShreveport, LouisianaShreveport is the third largest city in Louisiana. It is the principal city of the fourth largest metropolitan area in the state of Louisiana and is the 109th-largest city in the United States....
received PSIP data from KVBC-DT, and on the 29th decoded some frames of video, setting a new distance record in the process (1236 miles (1,989.1 km)). Oglethorpe would later receive frames from WKYC-DT in August (908 miles (1,461.3 km)). - On June 15, 2005, Oglethorpe received a test signal from KBEJ-TV (channel 2, Fredericksburg, TexasFredericksburg, TexasFredericksburg is the seat of Gillespie County, in the U.S. state of Texas. As of the 2010 Census estimate, the city had a population of 10, 530...
) by Sporadic E at a very short distance for this propagation mode: 327 miles (526.3 km). - On May 26, 2006, Westerberg received KBCO-FM's (97.3 MHz, Boulder, ColoradoBoulder, ColoradoBoulder is the county seat and most populous city of Boulder County and the 11th most populous city in the U.S. state of Colorado. Boulder is located at the base of the foothills of the Rocky Mountains at an elevation of...
) HD RadioHD RadioHD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...
stream via E's, the first such reception, at a distance of 1124 miles (1,808.9 km), and just two days later, picked up KAJA's (also 97.3 MHz, San Antonio, TexasSan Antonio, TexasSan Antonio is the seventh-largest city in the United States of America and the second-largest city within the state of Texas, with a population of 1.33 million. Located in the American Southwest and the south–central part of Texas, the city serves as the seat of Bexar County. In 2011,...
, 1004 miles (1,615.8 km) and KZPS's (92.5 MHz, Dallas, TexasDallas, TexasDallas is the third-largest city in Texas and the ninth-largest in the United States. The Dallas-Fort Worth Metroplex is the largest metropolitan area in the South and fourth-largest metropolitan area in the United States...
) HD Radio streams as well. - On June 25, 2007, Paul Farley in Sussex, UK received CJCN, Grand Falls Canada on channel A4 (67.25 MHz) at a distance of 3000 miles (4,828 km) via multi-hop Sporadic E. Signals were clear enough to watch and listen to the evening Newshour programme. The following day he received WUND Edenton, North Carolina at a distance of 3750 miles (6,035 km).
- In the summer of 2008, the recent introduction of the Coupon-eligible converter boxCoupon-eligible converter boxA coupon-eligible converter box was a digital television adapter that met eligibility specifications for subsidy "coupons" from the United States government...
, which was highly affordable, and tolerated multipath interference better than older ATSCATSCATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....
receivers, allowed many DXers in North America to receive and identify ATSC digital TV signals by Sporadic-E, something that had been very difficult to do in previous years. - On July 7, 2008, Daniel Albu from Bucharest Romania received via multi-hop Sporadic E SNRT Cahin(90,4 MHz) El jadida Morocco at a distance of 3216 kilometres (1,998.3 mi).
- On May 25, 2009 Daniel Albu from Bucharest, Romania received 2 radio stations from the United Arab Emirates, Radio Aziziah 88,7 MHz, and Holy Qu'ran Radio 88,2 MHz from Dubai at a distance of 3369 kilometres (2,093.4 mi).
- On June 26, 2009 Paul Logan from Lisnaskea, Northern Ireland, heard several stations from the United States and Canada including 90.7 WVAS Montgomery, AL, 90.7 WFUV New York, 94.1 WYSP Philadelphia, 95.1 WAYV Atlantic City NJ, 95.1 WXTK West Yarmouth MA, 97.3 WENJ Millville NJ, 97.3 WJFD New Bedford MA, 95.9 WOSC Cape Isle Of Wight MD, 95.9 WCRI Block Island RI, 98.1 WOCM Cape Isle Of Wight MD, and 92.1 CJOZ Bonavista ,Newfoundland, Canada. The event lasted for one hour starting at 2200 UTC. The reception of WVAS Montgomery, Alabama, USA at 4011 Miles / 6456 km at that time was a new world record for Sp E reception.
- A new world distance record for FM reception via Sporadic-E of 4302 miles/6924km was achieved by Mike Fallon in Sussex, England on May 31, 2010 when the religious station La Voz de la Luz in Salvaléon de Higüey, Dominican Republic was received and recorded on 88.7 MHz from 12:48 UTC for approximately 20 minutes. The recording was verified by the station to be their output.
- Also on May 31, 2010 at 13:20 UTC Paul Logan, Lisnaskea, Northern Ireland received signals from WRTU 89.7, San Juan, Puerto Rico at a distance of 3946 miles/6350 km. A recording of the programme "Latinorama" was confirmed by the stations programme director.
- On May 31, 2010 Partha Sarathi Goswami from Siliguri, West Bengal, India received radio stations from the Bangkok, Thailand, Balance FM 90 MHz, and DED National Radio 90.5 MHz from Bangkok at a distance of 1,640 kilometres (1,020 mi).
- Israel's IBA 88 FM Kol Israel from Tzefat on 87.6 MHz was received by Mike Fallon in Sussex, England on June 11, 2010 at 04:45 UTC via SpE propagation at a distance of 2173 miles/3497km.
- On June 14, 2010, 736 AM IST (Local Time) or 0206 UTC Partha Sarathi Goswami from Siliguri, West Bengal, India received radio station Thanh Hoá Radio from Thanh Hoá, Vietnam at an air distance of 1,940 kilometres (1,210 mi) with a Redsun 2100RP receiver and built in telescopic whip.
- On August 2, 2010, Paul Logan, Lisnaskea, Northern Ireland, received signals from 87.6 RCV-Rádio de Cabo Verde, Monte Verde, Cape Verde Islands at a distance of 4420 km/2746 miles.
Transequatorial propagation (TEP)
Discovered in 1947, transequatorial spread-F (TE) propagation makes it possible for reception of television and radio stations between 3000–5000 mi (4,828–8,046.7 km) across the equatorEquator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
on frequencies as high as 432 MHz. Reception of lower frequencies in the 30 – 70 MHz range are most common. If sunspot activity is sufficiently high, signals up to 108 MHz are also possible. Reception of TEP signals above 220 MHz is extremely rare. Transmitting and receiving stations should be nearly equidistant from the geomagnetic equator
L-shell
The L-shell, L-value, or McIlwain L-parameter is a parameter describing a particular set of planetary magnetic field lines. Colloquially, L-value often describes the set of magnetic field lines which cross the Earth's magnetic equator at a number of Earth-radii equal to the L-value...
.
The first large-scale VHF TEP communications occurred around 1957 – 58 during the peak of solar cycle 19. Around 1970, the peak of cycle 20, many TEP contacts were made between Australian and Japanese radio amateurs. With the rise of cycle 21 starting around 1977, amateur contacts were made between Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
/Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
and Southern Africa (both South Africa and Rhodesia
Rhodesia
Rhodesia , officially the Republic of Rhodesia from 1970, was an unrecognised state located in southern Africa that existed between 1965 and 1979 following its Unilateral Declaration of Independence from the United Kingdom on 11 November 1965...
/Zimbabwe
Zimbabwe
Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...
), and between Central and South America by TEP.
There are two distinctly different types of TEP: afternoon TEP and evening TEP.
Afternoon TEP
Afternoon TEP peaks during the mid-afternoon and early evening hours and is generally limited to distances of 4000–5000 mi (6,437.4–8,046.7 km). Signals propagated by this mode are limited to approximately 60 MHz. Afternoon TEP signals tend to have high signal strength and suffer moderate distortion due to multipath reflections.Evening TEP
The second type of TEP peaks in the evening around 1900 to 2300 hours local time. Signals are possible up to 220 MHz, and even very rarely on 432 MHz.Evening TEP is quenched by moderate to severe geomagnetic disturbances. The occurrence of evening TEP is more heavily dependent on high solar activity than is the afternoon type.
During late September 2001, from 2000 to 2400 local time, VHF television and radio signals from Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and Korea up to 220 MHz were received via evening transequatorial propagation near Darwin, Australia.
Earth – Moon – Earth (EME) propagation (Moonbounce)
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
. Moonbounce
EME (communications)
Earth-Moon-Earth, also known as moon bounce, is a radio communications technique which relies on the propagation of radio waves from an Earth-based transmitter directed via reflection from the surface of the Moon back to an Earth-based receiver....
allows communication on earth between any two points that can observe the moon at a common time.
Since the moon's mean distance from earth is 239000 miles (384,632.3 km), path losses are very high. It follows that a typical 240 dB
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
total path loss places great demand on high-gain receiving antennas, high-power transmissions, and sensitive receiving systems. Even when all these factors are observed, the resulting signal level is often just above the noise.
Because of the low signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
, as with amateur-radio practice, EME signals can generally only be detected using narrow-band receiving systems. This means that the only aspect of the TV signal that could be detected is the field scan modulation (AM vision carrier). FM broadcast signals also feature wide frequency modulation, hence EME reception is generally not possible. There are no published records of VHF/UHF EME amateur radio contacts using FM.
Notable Earth-Moon-Earth (EME) DX receptions
EME CH 68 (System-M)- During the mid 1970s, John Yurek, K3PGP, using a home-constructed, 24-foot (7.3 m), 0.6-focal-diameter parabolicParabolic reflectorA parabolic reflector is a reflective device used to collect or project energy such as light, sound, or radio waves. Its shape is that of a circular paraboloid, that is, the surface generated by a parabola revolving around its axis...
dish and UHF TV dipole feed-point tuned to channel 68, received KVST-68 Los AngelesLos ÁngelesLos Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
(1200 kW ERP) and WBTB-68 Newark, New JerseyNewark, New JerseyNewark is the largest city in the American state of New Jersey, and the seat of Essex County. As of the 2010 United States Census, Newark had a population of 277,140, maintaining its status as the largest municipality in New Jersey. It is the 68th largest city in the U.S...
via moonbounce. - At the time of the experiment there were only two known transmitters operating in the United States on UHF television channel 68, the main reason why this channel was selected for EME experiments.
For three nights in December 1978, astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
Dr. Woodruff T. Sullivan III
Woodruff T. Sullivan III
Woodruff T. Sullivan III is a U.S. physicist and astronomer, known primarily for his work in astrobiology, galactic astronomy, as well as for his role in the search for extraterrestrial intelligence ....
used the 305-metre Arecibo radio telescope
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
to observe the Moon at a variety of frequencies. This experiment demonstrated that the lunar surface is capable of reflecting terrestrial
Terrestrial television
Terrestrial television is a mode of television broadcasting which does not involve satellite transmission or cables — typically using radio waves through transmitting and receiving antennas or television antenna aerials...
band III (175 – 230 MHz) television signals back to earth. While not yet confirmed, FM broadcast EME reception may also be possible using the Arecibo dish antenna.
In 2002, physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
Dr. Tony Mann demonstrated that a single high-gain UHF yagi antenna
Yagi antenna
A Yagi-Uda array, commonly known simply as a Yagi antenna, is a directional antenna consisting of a driven element and additional parasitic elements...
, low noise masthead preamplifier, VHF/UHF synthesised communications receiver, and personal computer with FFT
Fast Fourier transform
A fast Fourier transform is an efficient algorithm to compute the discrete Fourier transform and its inverse. "The FFT has been called the most important numerical algorithm of our lifetime ." There are many distinct FFT algorithms involving a wide range of mathematics, from simple...
spectrum analyser
Spectrum analyzer
A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument. The primary use is to measure the power of the spectrum of known and unknown signals...
software could be used to successfully detect extremely weak UHF television carriers via EME.
Auroral propagation
An auroraAurora (astronomy)
An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...
is most likely to occur during periods of high solar activity when there is a high probability of a large solar flare
Solar flare
A solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy . The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day...
. When such an eruption occurs, charged particles from the flare may spiral towards earth arriving about a day later. This may or may not cause an aurora: if the interstellar magnetic field has same polarity, the particles do not get coupled to the geomagnetic field efficiently. Besides sunspot-related active solar surface areas, there are other solar phenomena that produce particles causing auroras, such as re-occurring coronal holes spraying out intense solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
. These charged particles are affected and captured by the geomagentic field and the various radiation belts
Van Allen radiation belt
The Van Allen radiation belt is a torus of energetic charged particles around Earth, which is held in place by Earth's magnetic field. It is believed that most of the particles that form the belts come from solar wind, and other particles by cosmic rays. It is named after its discoverer, James...
surrounding earth. The aurora-producing relativistic electrons eventually precipitate towards earth's magnetic poles, resulting in an aurora which disrupts short-wave communications (SID) due to ionospheric/magnetic storms in the D, E, and F layers. Various visual effects are also seen in the sky towards the north – aptly called the Northern Lights
Aurora (astronomy)
An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...
. The same effect occurs in the Southern Hemisphere, but the visual effects are towards the south. The auroral event starts by onset of geomagnetic storm, followed by number of sub-storms over the next day or so.
The aurora produces a reflecting sheet (or metric sized columns) which tends to lie in a vertical plane. The result of this vertical ionospheric "curtain" is reflection of signals well into the upper VHF band. The reflection is very aspect sensitive. Since the reflecting sheet lies towards the poles, it follows that reflected signals will arrive from that general direction. An active region or coronal hole may persist for some 27 days resulting in a second aurora when the Sun has rotated. There is a tendency for auroras to occur around the March/April, September/October equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...
periods, when the geomagnetic field is at right angle to Sun for efficient charged particle coupling. Signals propagated by aurora have a characteristic hum effect, which makes video and audio reception difficult. Video carriers, as heard on a communications receiver, no longer can be heard as a pure tone.
A typical radio aurora occurs in the afternoon, which produces strong and distorted signals for few hours. The local midnight sub-storming usually produces weaker signals, but with less distortion by Doppler from gyrating electrons.
Frequencies up to 200 MHz can be affected by auroral propagation.
Meteor scatter propagation
MeteorMETEOR
METEOR is a metric for the evaluation of machine translation output. The metric is based on the harmonic mean of unigram precision and recall, with recall weighted higher than precision...
scatter occurs when a signal bounces off a meteor's ionized trail.
When a meteor strikes earth's atmosphere, a cylindrical region of free electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s is formed at the height of the E layer. This slender, ionized column is relatively long, and when first formed is sufficiently dense to reflect and scatter television and radio signals, generally observable from 25 MHz upwards through UHF TV, back to earth. Consequently an incident television or radio signal is capable of being reflected up to distances approaching that of conventional Sporadic E propagation, typically about 1500 km. A signal reflected by such meteor ionisation can vary in duration from fractions of a second up to several minutes for intensely ionized trails. The events are classified as overdense and underdense, depending on the electron line-density (related to used frequency) of the trail plasma. The signal from overdense trail has a longer signal decay associated with fading and is a physically a reflection from the ionized cylinder surface, while an underdense trail gives a signals of short duration, which rises fast and decays exponentially and is scatter from individual electrons inside the trail.
Frequencies in the range of 50 to 80 MHz have been found to be optimum for meteor scatter propagation. The 88 – 108 MHz FM broadcast band is also highly suited for meteor scatter experiments. During the major meteor showers, with extremely intense trails, band III 175 – 220 MHz signal reception can occur.
Ionized trails generally reflect lower frequencies for longer periods (and produce stronger signals) compared to higher frequencies. For example, an 8-second burst on 45.25 MHz may only cause a 4-second burst at 90.5 MHz.
The effect of a typical visually seen single meteor (of size 0.5 mm) shows up as a sudden "burst" of signal of short duration at a point not normally reached by the transmitter. The combined effect of several meteors impinging on earth's atmosphere, while perhaps too weak to provide long-term ionisation, is thought to contribute to the existence of the night-time E layer.
The optimum time for receiving RF reflections off sporadic meteors is the early morning period, when the velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
of earth relative to the velocity of the particles is greatest which also increases the number of meteors occurring on the morning-side of the earth, but some sporadic meteor reflections can received at any time of the day, least in the early evening.
The annual major meteor showers are detailed below:
- January 3 – 4: QuadrantidsQuadrantidsThe Quadrantids are an easily visible January meteor shower.The radiant of this shower is an area inside the constellation Boötes. The name comes from Quadrans Muralis, an obsolete constellation that is now part of Boötes...
- April 22 – 23: LyridsLyridsThe Lyrids are a strong meteor shower lasting from April 16 to April 26 each year. The radiant of the meteor shower is located in the constellation Lyra, peaking at April 22—hence they are also called the Alpha Lyrids or April Lyrids. The source of the meteor shower is the periodic Comet...
- May 5 – 6: Eta Aquariids
- June 9 – 10: ArietidsArietidsThe Arietids are a strong meteor shower that lasts from May 22 to July 2 each year, and peaks on June 7. The Arietids, along with the Zeta Perseids, are the most intense daylight meteor showers of the year...
& zeta-Perseids - August 12 – 13: PerseidsPerseidsThe Perseids are a prolific meteor shower associated with the comet Swift-Tuttle. The Perseids are so-called because the point from which they appear to come, called the radiant, lies in the constellation Perseus. The name derives in part from the word Perseides , a term found in Greek mythology...
- October 21 – 22: OrionidsOrionidsThe Orionid meteor shower, usually shortened to the Orionids, is the most prolific meteor shower associated with Halley's Comet. The Orionids are so-called because the point they appear to come from, called the radiant, lies in the constellation Orion. Orionids are an annual meteor shower which...
- November 3 – 5: TauridsTauridsThe Taurids are an annual meteor shower associated with the comet Encke. They are named after their radiant point in the constellation Taurus, where they are seen to come from in the sky...
- November 16 – 18: LeonidsLeonidsThe Leonids is a prolific meteor shower associated with the comet Tempel-Tuttle. The Leonids get their name from the location of their radiant in the constellation Leo: the meteors appear to radiate from that point in the sky. They tend to peak in November.Earth moves through the meteoroid...
(Note: activity varies, outburst only at about 33 year interval) - December 13 – 14: GeminidsGeminidsThe Geminids are a meteor shower caused by the object 3200 Phaethon, which is thought to be a Palladian asteroid. This would make the Geminids, together with the Quadrantids, the only major meteor showers not originating from a comet...
- December 22 – 23: UrsidsUrsidsThe Ursids meteor activity begins annually around December 17th and runs for a week plus, until the 25th or 26th. This meteor shower is named for its radiant point which is located near the star Beta Ursae Minoris in the constellation Ursa Minor....
For observing meteor shower-related radio signals, the shower's radiant must be above the (propagation mid path) horizon. Otherwise no meteor of the shower can hit the atmosphere along the propagation path and no reflections from shower's meteor trails can be observed.
Satellite UHF TVRO DX
Although not by strict definition terrestrial TV DX, satelliteSatellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
UHF TVRO reception is related in certain aspects. For example, reception of satellite signals requires sensitive receiving systems and large outdoor antenna systems. However, unlike terrestrial TV DX, satellite UHF TV reception is far easier to predict. The geosynchronous satellite at 22375 miles (36,009 km) height is a line of sight reception source. If the satellite is above the horizon, it can be generally received, if it is below the horizon, reception is not possible.
Notable Satellite UHF TVRO DX receptions
- In December 1975, Stephen Birkill, Sheffield, England, was the first DXer to receive viewable pictures from the 860 MHz Indian ATS-6 satelliteSatelliteIn the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
, which was in synchronous orbitSynchronous orbitA synchronous orbit is an orbit in which an orbiting body has a period equal to the average rotational period of the body being orbited , and in the same direction of rotation as that body.-Properties:...
over Central AfricaCentral AfricaCentral Africa is a core region of the African continent which includes Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, and Rwanda....
, for the purpose of providing educationEducationEducation in its broadest, general sense is the means through which the aims and habits of a group of people lives on from one generation to the next. Generally, it occurs through any experience that has a formative effect on the way one thinks, feels, or acts...
al television programTelevision programA television program , also called television show, is a segment of content which is intended to be broadcast on television. It may be a one-time production or part of a periodically recurring series...
s to the Indian subcontinentIndian subcontinentThe Indian subcontinent, also Indian Subcontinent, Indo-Pak Subcontinent or South Asian Subcontinent is a region of the Asian continent on the Indian tectonic plate from the Hindu Kush or Hindu Koh, Himalayas and including the Kuen Lun and Karakoram ranges, forming a land mass which extends...
. - In 1978, Ian Roberts, South Africa, received 714 MHz television pictures from the SovietSoviet UnionThe Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
UHF Ekran-class Statsionar-T satellite.
Digital modes
Digital radioDigital radio
Digital radio has several meanings:1. Today the most common meaning is digital radio broadcasting technologies, such as the digital audio broadcasting system, also known as Eureka 147. In these systems, the analog audio signal is digitized into zeros and ones, compressed using formats such as...
and digital television
Digital television
Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...
can also be received, however there is much greater difficulty with reception of weak signals due to the cliff effect
Cliff effect
In telecommunications, the cliff effect or brickwall effect describes the sudden loss of digital signal reception. Unlike analog signals, which gradually fade when signal strength decreases or electromagnetic interference or multipath increases, a digital signal provides data which is either...
, particularly with the ATSC
ATSC
ATSC standards are a set of standards developed by the Advanced Television Systems Committee for digital television transmission over terrestrial, cable, and satellite networks....
TV standard mandated in the U.S. For DVB-T
DVB-T
DVB-T is an abbreviation for Digital Video Broadcasting — Terrestrial; it is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in the UK in 1998...
, hierarchical modulation
Hierarchical modulation
Hierarchical modulation, also called layered modulation, is one of the signal processing techniques for multiplexing and modulating multiple data streams into one single symbol stream, where base-layer symbols and enhancement-layer symbols are synchronously overplayed before...
may allow a lower-definition signal to be received even if the details of the full signal cannot be decoded. A unique issue observed on analog TV at the end of the DTV transition in the United States
DTV transition in the United States
The DTV transition in the United States was the switchover from analog to exclusively digital broadcasting of free over-the-air television programming...
was that very distant analog stations were viewable in the hours after the permanent shutdown of local analog transmitters in June 2009. This was particularly pronounced because June is one of the strongest months for DX reception on VHF, and most digital stations were assigned to UHF.
See also
- Federal Standard 1037CFederal Standard 1037CFederal Standard 1037C, titled Telecommunications: Glossary of Telecommunication Terms is a United States Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended....
- MW DXMW DXMW DX, short for mediumwave DXing, is the hobby of receiving the reception of distant mediumwave radio stations. MW DX is similar to TV and FM DX in that broadcast band stations are the reception targets...
- SkywaveSkywaveSkywave is the propagation of electromagnetic waves bent back to the Earth's surface by the ionosphere. As a result of skywave propagation, a broadcast signal from a distant AM broadcasting station at night, or from a shortwave radio station can sometimes be heard as clearly as local...
- Radio propagationRadio propagationRadio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
- Thermal fadeThermal fadeA thermal fade is a phenomenon of wireless signal degradation caused by temperature and relative humidity factors. As the prevailing environmental conditions change, for example, from hot to cool, humid to arid or day to night, the electromagnetic waves refract differently thus altering the power...
- Clear-channel station
External links
- TV/FM Antenna Locator
- Worldwide TV/FM DX Association
- Worldwide TV/FM DX Association Forums
- Skywaves DX Groups, Home of FM & TV DX in the UK
- Girard Westerberg's page, including a live DX webcam
- Mike's TV and FM DX Page since 1999
- Todd Emslie's TV FM DX Page
- Jeff Kadet's TV DX Page
- Matt Sittel's DX Page
- FM DX Italy The official FM & TV DX website in Italy
- Siciliamedia Home of FM & TV DX in Sicily
- FMLIST is a non-commercial worldwide database of FM stations, including a bandscan and logbook tool (FMINFO/myFM)
- Mixture.fr AM/FM/DAB database for France
- MeteorComm Meteor Burst Technology used for Data Communication
- FMSCAN reception prediction of FM, TV, MW, SW stations (also use the expert options for better results)
- Herman Wijnants' FMDX pages
- TV/FM Skip Log
- qth.net Mailing Lists for Radio, Television, Amateur and other related information for Enthusiasts.
- North American TV Logo Gallery
- VHF DXing - From Fort Walton Beach, Florida
- Radio-info.com DX and Reception
- FM DX RDS LogBook Software
- VHF-DX network in South America and The Caribbean