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TV DX and FM DX are two terms, customarily grouped together, that refer to long-distance reception of TV and FM radio stations, respectively. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic See also Frequency modulation, FM band FM broadcasting is a broadcast Technology invented by Edwin Howard Armstrong that Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. The term DX is an old telegraphic term meaning "long distance. 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 " These terms refer to the active search for distant radio or television stations received during unusual tropospheric lower atmospheric weather-related, or E-layer and F2-layer upper atmospheric ionospheric conditions. This article is about radio broadcasting for other uses see Radio (disambiguation. A television station is a type of broadcast station that broadcasts both audio and Video to Television receivers in a particular area The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five The weather is a set of all the phenomena occurring in a given Atmosphere at a given Time. The ionosphere is the uppermost part of the atmosphere, distinguished because it is Ionized by solar radiation

VHF/UHF television and radio signals are normally limited to a maximum "deep fringe" reception service area of approximately 40 – 100 miles (60 – 160 kilometers) in areas where the broadcast spectrum is congested, and about 50 percent farther in the absence of interference. Very high frequency (VHF is the Radio frequency range from 30 MHz to 300 MHz. A mile is a unit of Length, usually used to measure Distance, in a number of different systems including Imperial units United States The kilometre ( American spelling: kilometer) symbol km is a unit of Length in the Metric system, equal to one thousand However, providing favourable atmospheric conditions are present, television and radio signals can sometimes 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. An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into A tuner is an adjustable device which passes one Radio Frequency, or band of frequencies and excludes others by using electrical Resonance. This article is about a radio receiver for other uses see Radio (disambiguation.

While only a limited number of local stations can be normally 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. A hobby is a spare-time Recreational pursuit Etymology A Hobby horse is a wooden or Wickerwork toy made to be 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. Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications MW DX, short for Mediumwave DXing, is the hobby of receiving the reception of distant Mediumwave (known as Shortwave Radio operates between the frequencies of 3000 KHz (3 [1]

Contents

History

After the introduction of the Alexandra Palace, 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. Set in Alexandra Park, Alexandra Palace was built in an area spanning Wood Green and Muswell Hill, North London, England in 1873 as London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. The 405-line Monochrome analogue Television broadcasting system was the first fully electronic television system to be used in regular broadcasting Year 1936 ( MCMXXXVI) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian calendar. 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. Year 1938 ( MCMXXXVIII) was a Common year starting on Saturday (link will display the full calendar of the Gregorian calendar. RCA Corporation, founded as Radio Corporation of America, was an electronics company in existence from 1919 to 1986 Riverhead New York may refer to Riverhead (town New York Riverhead (CDP New York, within the town of Riverhead The kilometre ( American spelling: kilometer) symbol km is a unit of Length in the Metric system, equal to one thousand The ionosphere is the uppermost part of the atmosphere, distinguished because it is Ionized by solar radiation 0 MHz, 405-line channel B1 TV service. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. 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. Jasmine Lydia Bligh ( May 20 1913 &ndash July 21 1991) was one of the first three BBC Television Service presenters in the 1930s Elizabeth Cowell was one of the first three BBC Television Service presenters along with Jasmine Bligh and Leslie Mitchell. A logo ( Greek el λογότυπος = el-Latn logotypos is a graphical element ( Ideogram, Symbol, Emblem, Icon, Sign) Broadcast programming, or scheduling, is the practice of organizing Television or Radio programs in a daily weekly or season-long schedule 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. This article is mainly concerned with Still photography film For Motion picture film please see Film stock. [2]

The BBC temporarily ceased transmissions on September 1, 1939 as World War II began. Events 462 - Possible start of first Byzantine indiction cycle. Year 1939 ( MCMXXXIX) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including 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. Year 1946 ( MCMXLVI) was a Common year starting on Tuesday (link will display full 1946 calendar of the Gregorian calendar. Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest The Republic of South Africa (also known by other official names) is a country located at the southern tip of the continent of Africa India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country The Middle East is a Subcontinent with no clear boundaries often used as a synonym to Near East, in opposition to Far East. The Caribbean (ˌkærəˡbiən kæ'rəbiən Cariben|Caraïben or Caraïben; Caraïbe or more commonly Antilles; Caribe is a Region consisting

In May 1940, the Federal Communications Commission (FCC) U. Year 1940 ( MCMXL) was a Leap year starting on Monday (link will display the full 1940 calendar of the Gregorian calendar. 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 1,400 miles (2,250 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. Year 1942 ( MCMXLII) was a Common year starting on Thursday (the link will display the full 1942 calendar of the Gregorian calendar. 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. Chicago (ʃɪˈkɑːgoʊ is the largest City by population in the state of Illinois and the American Midwest of the United States. This article is about the Mexican city for other uses see Monterrey (disambiguation. 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. "[3]

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. Year 1945 ( MCMXLV) was a Common year starting on Monday (link will display the full calendar 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. [4]

During the 1950s to early 1960s, long-distance television reports started to circulate via popular U. The 1950s Decade refers to the years of 1950 to 1959 inclusive The 1960s decade refers to the years from the beginning of 1960 to the end of 1969 S. electronics hobbyist periodicals such as DXing Horizons, Popular Electronics, Television Horizons, Radio Horizons, and Radio-Electronics. Magazines, periodicals or serials are Publications generally published on a regular schedule containing a variety of articles, generally Popular Electronics was a magazine started by Ziff-Davis Publishing in October 1954 for hobbyist and experimenters in electronics Radio-Electronics magazine was published under various titles from 1929 to 2002 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 10,800 miles (17,400 km) with the reception of England's BBC channel 1 in various parts of Australia. Year 1957 ( MCMLVII) was a Common year starting on Tuesday (link displays the 1957 Gregorian calendar) For a topic outline on this subject see List of basic Australia topics. Most notably, George Palmer in Melbourne, Victoria, received viewable pictures and audio of a news program from the BBC London channel B1 station. Melbourne ( is the second most populous city in Australia, with a Metropolitan area population of approximately 3 This BBC F2 reception was recorded on movie film. [5]

During the early 1960s, the U.K. magazine Practical Television first published a regular TV DX column edited by Charles Rafarel. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Practical Television, later known as Television and subsequently Television & Consumer Electronics, was a UK magazine for the electronics/TV 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. TV DX and FM DX are two terms customarily grouped together that refer to long-distance reception of TV and FM Radio stations respectively With the demise of Television Magazine in December 2006, 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. Year 1981 ( MCMLXXXI) was a Common year starting on Thursday (link displays the 1981 Year 1986 ( MCMLXXXVI) was a Common year starting on Wednesday (link displays 1986 Gregorian calendar)

Tropospheric propagation

Meteorologist William Hepburn's forecast maps often provide early indications of potential tropospheric DX openings.
Meteorologist William Hepburn's forecast maps often provide early indications of potential tropospheric DX openings.

The service area from a TV or FM radio transmitter extends to just beyond the optical horizon, at which point signals start to rapidly reduce in strength. Viewers living in such a "deep fringe" reception area will notice that during certain conditions, weak signals normally masked by noise increase in signal strength to allow quality reception. Such conditions are related to the current state of the troposphere. The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and

Tropospheric propagated signals travel in the part of the atmosphere adjacent to the surface and extending to some 25,000 feet (7,620 meters). Tropospheric scatter (or troposcatter) is the scattering of distant TV and FM radio stations by the Troposphere so that they travel farther than Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International Such signals are thus directly affected by weather conditions extending over some hundreds of miles. The weather is a set of all the phenomena occurring in a given Atmosphere at a given Time. During very settled, warm anticyclonic weather (i. In Meteorology, a cyclone refers to an area of closed circular fluid motion rotating in the same direction as the Earth. e. , high pressure), usually weak signals from distant transmitters improve in strength. Another symptom during such conditions may be interference to the local transmitter resulting in co-channel interference, usually horizontal lines or an extra floating picture. In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern A settled high-pressure system gives the characteristic conditions for enhanced tropospheric propagation, in particular favouring signals which travel along the prevailing isobar pattern (rather than across it). Such weather conditions can occur at any time, but generally the summer and autumn months are the best periods. Summer is one of the four Temperate Seasons Summer marks the warmest time of year with the longest days Autumn (also known as fall in North American English) is one of the four Temperate Seasons Autumn marks the transition from Summer In certain favourable locations, enhanced tropospheric propagation may enable reception of UHF TV signals up to 1,000 miles (1,600 km) or more.

The observable characteristics of such high-pressure systems are usually clear, cloudless days with little or no wind. A cloud is a visible mass of droplets or frozen crystals floating in the atmosphere above the surface of the Earth or another Planetary body Wind is the flow of Air or other Gases that compose an Atmosphere (including but not limited to the Earth's) At sunset the upper air cools, as does the surface temperature, but at different rates. Sunset, also called sundown in some American English Dialects is the instant when the trailing edge of the Sun 's disk disappears below This produces a boundary or temperature gradient, which allows an inversion level to form – a similar effect occurs at sunrise. In atmospheric sciences ( Meteorology, Climatology and related fields the temperature gradient (typically of air, more generally of any Fluid In meteorology an inversion is a deviation from the normal change of an atmospheric property with altitude Sunrise is the instant at which the upper edge of the Sun appears above the Horizon in the East. The inversion is capable of allowing VHF and UHF signal propagation well beyond the normal radio horizon distance. In Telecommunication, radio horizon is the locus of points at which direct rays from an antenna are tangential to the surface of the Earth

The inversion effectively reduces sky wave radiation from a transmitter – normally VHF and UHF signals travel on into space when they reach the horizon, the refractive index of the ionosphere preventing signal return. Skywave is the propagation of electromagnetic waves bent (refracted back to the Earth's surface by the Ionosphere. Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy The horizon ( Ancient Greek ὁ ὁρίζων, /ho horídzôn/ from ὁρίζειν, "to limit" is the apparent line that separates The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium With temperature inversion, however, the signal is to a large extent refracted over the horizon rather than continuing along a direct path into outer space. Refraction is the change in direction of a Wave due to a change in its Speed. Outer space, often simply called space, comprises the relatively empty regions of the Universe outside the escape velocities of Celestial bodies.

Fog also produces good tropospheric results, again due to inversion effects. Fog is a cloud that is in contact with the ground Stratus clouds are usually the only clouds that touch the ground Fog occurs during high-pressure weather, and if such conditions result in a large belt of fog with clear sky above, there will be heating of the upper fog level and thus an inversion. This situation often arises towards night fall, continues overnight and clears with the sunrise over a period of around 4 – 5 hours.

Tropospheric ducting

This example of 1,340-mile (2,156 km) tropospheric ducting reception shows Auckland, New Zealand 175.25 MHz ch4 TV received by Robert Copeman, Sydney, Australia.
This example of 1,340-mile (2,156 km) tropospheric ducting reception shows Auckland, New Zealand 175. The Auckland metropolitan area or Greater Auckland, in the North Island of New Zealand, is the largest and most populous urban area in the country 25 MHz ch4 TV received by Robert Copeman, Sydney, Australia.

Tropospheric ducting is a type of radio propagation that tends to happen during periods of stable, anticyclonic weather. In this propagation method, when the signal encounters a rise in temperature in the atmosphere instead of the normal decrease (known as a temperature inversion), the higher refractive index of the atmosphere there will cause the signal to be bent. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium Tropospheric ducting affects all frequencies, and signals enhanced this way tend to travel up to 800 miles (1,300 km) (though some people have received "tropo" beyond 1,000 miles / 1,600 km), while with tropospheric-bending, stable signals with good signal strength from 500+ miles (800+ km) away are not uncommon when the refractive index of the atmosphere is fairly high.

Tropospheric ducting of UHF television signals is relatively common during the summer and autumn months, and is the result of change in the refractive index of the atmosphere at the boundary between air masses of different temperatures and humidities. Summer is one of the four Temperate Seasons Summer marks the warmest time of year with the longest days Autumn (also known as fall in North American English) is one of the four Temperate Seasons Autumn marks the transition from Summer Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity. Using an analogy, it can be said that the denser air at ground level slows the wave front a little more than does the rare upper air, imparting a downward curve to the wave travel. Analogy is both the cognitive process of transferring Information from a particular subject (the analogue or source to another particular subject (the target and The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different

Ducting can occur on a very large scale when a large mass of cold air is overrun by warm air. This is termed a temperature inversion, and the boundary between the two air masses may extend for 1,000 miles (1,600 km) or more along a stationary weather front. A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena.

Temperature inversions occur most frequently along coastal areas bordering large bodies of water. This is the result of natural onshore movement of cool, humid air shortly after sunset when the ground air cools more quickly than the upper air layers. The same action may take place in the morning when the rising sun warms the upper layers.

Even though tropospheric ducting has been occasionally observed down to 40 MHz, the signal levels are usually very weak. Higher frequencies above 90 MHz are generally more favourably propagated.

High mountainous areas and undulating terrain between the transmitter and receiver can form an effective barrier to tropospheric signals. A mountain is a Landform that extends above the surrounding Terrain in a limited area with a peak Ideally, a relatively flat land path between the transmitter and receiver is ideal for tropospheric ducting. Sea paths also tend to produce superior results.

In certain parts of the world, notably the Mediterranean Sea and the Persian Gulf, tropospheric ducting conditions can become established for many months of the year to the extent that viewers regularly receive quality reception of signals over distances of 1,000 miles (1,600 km). The Persian Gulf, in the Southwest Asian region is an extension of the Such conditions are normally optimum during very hot settled summer weather.

Tropospheric ducting over water, particularly between California and Hawaii, Brazil and Africa, Australia and New Zealand, Australia and Indonesia, and Bahrain and Pakistan, has produced VHF/UHF reception ranging from 1,000 to 3,000 miles (1,600 – 4,800 km). California ( is a US state on the West Coast of the United States, along the Pacific Ocean. The State of Hawaii ( or həˈwaɪʔiː Hawaiian: Mokuāina o Hawaii) is a state in the United States located on an Archipelago in the |utc_offset = -2 to -4 |time_zone_DST = BRST |utc_offset_DST = -2 to -5 |cctld New Zealand is an Island country in the south-western Pacific Ocean comprising two main landmasses (the North Island and the South Island The Republic of Indonesia ( (Republik Indonesia is a Country in Southeast Asia. The Kingdom of Bahrain (in مملكة البحرين,, literally Kingdom of the Two Seas) is an Island country in the Persian Gulf Pakistan () officially the Islamic Republic of Pakistan, is a country located in South Asia, Southwest Asia, Middle East and

Tropospheric signals exhibit a slow cycle of fading and will occasionally produce signals sufficiently strong for noise-free stereo, reception of RDS data, and solid locks of HD Radio streams on FM or noise-free, color TV pictures. Stereophonic sound, commonly called stereo, is the reproduction of Sound, using two or more independent audio channels through a Symmetrical HD Radio is the name used by iBiquity for a system of digital transmission for audio broadcast stations Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic

Virtually all long-distance reception of digital television occurs by tropospheric ducting (due to most, but not all, DTV stations broadcasting in the UHF band). Digital television (DTV is the sending and receiving of moving images and sound by discrete ( digital) signals in contrast to the analog signals used by

Notable tropospheric DX receptions

An elaborate band 3 / UHF TV DX aerial system used by Rijn Muntjewerff (Netherlands).
An elaborate band 3 / UHF TV DX aerial system used by Rijn Muntjewerff (Netherlands).

Sporadic E propagation (E-skip)

This example of 1,400-mile (2,250 km) Sporadic E reception shows Te Aroha, New Zealand 45.24 MHz ch1 TV received by Todd Emslie, Sydney, Australia.
This example of 1,400-mile (2,250 km) Sporadic E reception shows Te Aroha, New Zealand 45. Te Aroha is a rural town in the Thames Valley region of New Zealand with a population of 3768 (2006 census 24 MHz ch1 TV received by Todd Emslie, Sydney, Australia.

Sporadic E, also called E-skip, is the phenomenon of irregularly scattered patches of relatively dense ionization that develop seasonally within the E region of the ionosphere and reflect TV and FM frequencies, generally up to about 150 MHz. Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons The Kennelly-Heaviside layer, also known as the E region or simply the Heaviside layer, is a layer of ionised Gas occurring at 90&ndash150 km The ionosphere is the uppermost part of the atmosphere, distinguished because it is Ionized by solar radiation When frequencies reflect off multiple patches, it is referred to as multi-hop skip. E-skip allows radio waves to travel a thousand miles or even more beyond their intended area of reception. Radio waves are electromagnetic waves occurring on the Radio frequency portion of the Electromagnetic spectrum. 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. Shortwave Radio operates between the frequencies of 3000 KHz (3 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 (105 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). Medium Wave (MW is a part of the Medium frequency (MF radio band used mainly for AM broadcasting. 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). Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball' Southern Hemisphere is the half of a Planet that is South of the Equator —the word hemisphere literally means 'half ball' A small peak of activity is also usually noted in mid-winter.

The length of a single-hop E-skip path varies between approximately 450 and 1,500 miles (720 – 2,400 km). At times, double-hop Sporadic E can propagate signals over a 1,900 to 2,900-mile (3,100 – 4,700 km) path. During periods of extremely widespread Es ionisation, multi-hop signals up to 60 MHz have been received out to 5,000 miles (8,000 km). Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons

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. Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations Long single-hop (900 – 1,500 miles / 1,450 – 2,400 km) Sporadic E television signals tend to be more stable and relatively free of multipath images. Shorter-skip (400 – 800 miles / 650 – 1,300 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. The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0 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). Sporadic E or Es is an unusual form of Radio propagation utilizing characteristics of the earth's Ionosphere. Very high frequency (VHF is the Radio frequency range from 30 MHz to 300 MHz. The typical expected distances are about 600 to 1,400 miles (970 – 2,250 km). However, under exceptional circumstances, a highly ionized Es cloud can propagate band I VHF signals down to approximately 350 miles (550 km). When short-skip Es reception occurs, i. e. , under 500 miles (800 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 is a Region of Oceania: New Zealand, Australia, Papua New Guinea, and neighbouring Islands in the Pacific

Equatorial E-skip

Equatorial 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. The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the Winter is one of the four Seasons of Temperate zones Calculated astronomically, it begins on the Solstice and ends on the Equinox 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

Roof mounted 40-90 MHz band 1 VHF TV DX aerial system used by Rijn Muntjewerff (Netherlands).
Roof mounted 40-90 MHz band 1 VHF TV DX aerial system used by Rijn Muntjewerff (Netherlands).

On July 20[17] 2003, Paul Logan, Lisnaskea, Northern Ireland achieved a second reception of CBAF Moncton, New Brunswick on 88. Events 363 - Roman Emperor Julian is killed during the retreat from the Sassanid Empire. Year 2003 ( MMIII) was a Common year starting on Wednesday of the Gregorian calendar. Ireland (pronounced /ˈaɾlənd/ Éire) is the third largest island in Europe, and the twentieth-largest island in the world The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Events 1099 - The First Crusade: The Siege of Jerusalem begins Events 1304 - Wars of Scottish Independence: Fall of Stirling Castle - King Edward I of England takes the last rebel stronghold 5 MHz at 02:15 local time.

F2 propagation (F2-skip)

This example of 8,490-mile (13,660 km) F2 reception shows Grünten Germany 48.26 MHz chE2 TV received by Tony Mann, Perth, Western Australia.
This example of 8,490-mile (13,660 km) F2 reception shows Grünten Germany 48. 26 MHz chE2 TV received by Tony Mann, Perth, Western Australia.

The E layer of the ionosphere is not the only layer that can reflect VHF television signals. Less frequently, the higher F2 layer can also propagate VHF signals several thousand miles beyond their intended area of reception.

Solar activity has a cycle of approximately 11 years. The solar cycle, or the solar magnetic activity cycle, is the main source of periodic variation of all solar phenomena driving variations in Space weather. During this period, sunspot activity rises to a peak and gradually falls again to a low level. When sunspot activity increases, the reflecting capabilities of the F1 layer surrounding earth enable high frequency short-wave communications. A sunspot is a region on the Sun 's surface ( Photosphere) that is marked by intense magnetic activity which inhibits Convection, forming The highest-reflecting layer, the F2 layer, which is approximately 200 miles (320 km) above earth, receives ultraviolet radiation from the sun, causing ionisation of the gases within this layer. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays The Sun (Sol is the Star at the center of the Solar System. Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons During the daytime when sunspot activity is at a maximum, the F2 layer can become intensely ionized due to radiation from the sun. The Sun (Sol is the Star at the center of the Solar System. When solar activity is sufficiently high, the MUF (Maximum Usable Frequency) rises, hence the ionisation density is sufficient to reflect signals well into the 30 – 50 MHz VHF spectrum. Since the MUF progressively increases, F2 reception on lower frequencies can indicate potential low band 45-55 MHz VHF TV paths. A rising MUF will initially affect the 27 MHz CB band, and the amateur 28 MHz 10 meters band before reaching 45-55 MHz TV. Citizens' Band radio ( CB) is in many countries a system of short-distance simplex radio communications between individuals on a selection of 40 channels within The F2 MUF generally increases at a slower rate compared to the Es MUF.

Since the height of the F2 layer is some 200 miles (320 km), it follows that single-hop F2 signals will be received at thousands rather than hundreds of miles. A single-hop F2 signal will usually be around 2,000 miles (3,200 km) minimum. A maximum F2 single-hop can reach up to approximately 3,000 miles (4,800 km). Multi-hop F2 propagation has enabled low-band VHF reception to over 11,000 miles (17,700 km).


Since F2 reception is directly related to radiation from the Sun on both a daily basis and in relation to the sunspot cycle, it follows that for optimum reception the centre of the signal path will be roughly at midday.

The F2 layer tends to predominantly propagate signals below 40 MHz, which includes the 27 MHz CB band, and 28 MHz 10-metre Amateur radio band. Citizens' Band radio ( CB) is in many countries a system of short-distance simplex radio communications between individuals on a selection of 40 channels within Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications Less frequently, television signals in the 45 – 55 MHz VHF band are also propagated over considerable distances. In North America, F2 is most likely to only affect VHF channel 2.

Television pictures propagated via F2 tend to suffer from characteristic ghosting and smearing. Picture degradation and signal strength attenuation increases with each subsequent F2 hop.

Notable F2 DX receptions

Transequatorial propagation (TEP)



Discovered in 1947, transequatorial spread-F (TE) propagation makes it possible for reception of television and radio stations between 3,000 – 5,000 miles (4,800 – 8,000 km) across the equator on frequencies as high as 432 MHz. The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the 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. Earth 's magnetic field (and the surface magnetic field) is approximately a Magnetic dipole, with one pole near the North pole (see The L-shell, L-value, or McIlwain L-parameter (after Carl McIlwain) is a parameter describing a particular set of planetary magnetic field lines

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. Greece (Ελλάδα transliterated: Elláda, historically, Ellás,) officially the Hellenic Republic (Ελληνική Δημοκρατία Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest Rhodesia was the name adopted when the formerly British colony of Southern Rhodesia declared itself independent ( Unilateral Declaration of Independence See also Great Zimbabwe National Monument. For information about the March and June 2008 presidential elections see Zimbabwean presidential election

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 4,000 – 5,000 miles (6,400 – 8,000 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 and Korea up to 220 MHz were received via evening transequatorial propagation near Darwin, Australia. For a topic outline on this subject see List of basic Japan topics. [27]

Earth – Moon – Earth (EME) propagation (Moonbounce)

Image:Arecibo Overview.jpg
The Arecibo Radio Telescope spherical reflector antenna has been used for detecting terrestrial television signals reflected off the lunar surface.

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. 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 [28]

Since the moon's mean distance from earth is 239,000 miles (384,000 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. The decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to 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. Signal-to-noise ratio (often abbreviated SNR or S/N) is an Electrical engineering concept also used in other fields (such as scientific Measurements 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.

While not yet confirmed, the 1000 ft (305-metre) Arecibo radio telescope may be capable of receiving weak EME television signals. The Arecibo Observatory is a very sensitive Radio telescope located approximately south-southwest from the town of Arecibo in Puerto Rico. Based on mathematical calculations assuming 60 dB antenna gain, FM broadcast EME reception may also be possible using the Arecibo dish antenna. Mathematics is the body of Knowledge and Academic discipline that studies such concepts as Quantity, Structure, Space and

Notable Earth-Moon-Earth (EME) DX receptions

For three nights in December 1978, astronomer Dr. Historically Astronomy was more concerned with the classification and description of phenomena in the sky while Astrophysics attempted to explain these phenomena Woodruff T. Sullivan III used the 305-metre Arecibo radio telescope to observe the Moon at a variety of frequencies. Woodruff T Sullivan III ( "Woody" Sullivan) (born 1944) is a U The Arecibo Observatory is a very sensitive Radio telescope located approximately south-southwest from the town of Arecibo in Puerto Rico. This experiment demonstrated that the lunar surface is capable of reflecting terrestrial band III (175 – 230 MHz) television signals back to earth. Terrestrial television is a term which refers to modes of television broadcasting which do not involve satellite transmission [30]

In 2002, physicist Dr. A physicist is a Scientist who studies or practices Physics. Physicists study a wide range of physical phenomena in many branches of physics spanning 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. A Yagi-Uda Antenna, commonly known simply as a Yagi antenna or Yagi, is a Directional antenna system consisting of an array of a dipole A spectrum analyzer or spectral analyzer is a device used to examine the spectral composition of some electrical, acoustic, or optical [31]

Auroral propagation



An aurora is most likely to occur during periods of high solar activity when there is a high probability of a large solar flare. A solar flare is a violent explosion in a star's (like the Sun 's atmosphere releasing as much Energy as 6 × 1025 Joules Solar flares 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 Aurora: if the interstellar magnetic field has same polarity, the particles do not get coupled to geomagentic field efficiently. Besides sunspot-related active solar surface areas, there are other solar pheomena that produce particles causing Auroras, such as re-occurring coronal holes spraying out intense solar wind. These charged particles are affected and captured by geomagentic field and the various radiation belts surrounding earth. The Van Allen radiation belt is a Torus of energetic Charged particles ( plasma) around Earth, held in place by Earth's Magnetic 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 even 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. An equinox is the event of the Sun passing over the Earth's equator in its annual cycle 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

Meteor scatter occurs when a signal bounces off a meteor's ionized trail.

When a meteor strikes earth's atmosphere, a cylindrical region of free electrons is formed at the height of the E layer. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J 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. In Physics, velocity is defined as the rate of change of Position.

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. The Quadrantids are a strong January Meteor shower. The radiant of this shower is an area inside the Constellation Boötes. Lyra (ˈlaɪrə Lyre) is one of the 48 Constellations listed by Ptolemy, and is one of the 88 modern constellations recognized by the International Table of meteor showers Note This list of meteor streams and peak activity times is based on data from the International Meteor Organization while most of the parent The Perseids (ˈpɝsiːɨdz pûr'sē-ĭdz is a prolific Meteor shower associated with the Comet Swift-Tuttle. Table of meteor showers Note This list of meteor streams and peak activity times is based on data from the International Meteor Organization while most of the parent Table of meteor showers Note This list of meteor streams and peak activity times is based on data from the International Meteor Organization while most of the parent For a list of famous people named Leonid please see Leonid (a disambiguation page The Geminids are a Meteor shower caused by an object named 3200 Phaethon, which is thought to be an extinct Comet. The Ursids meteor activity begins annually around December 17th and runs for a week plus until the 25th or 26th. Otherwise no meteor of the shower can hit the atmoshere along the propagation path and no reflections from shower's meteor trails can be observed.

Satellite TVRO UHF TV DX

Although not by strict definition terrestrial TV DX, satellite UHF TVRO reception is related in certain aspects. This article is about artificial satellites For natural satellites also known as moons see Natural satellite. Television receive-only, or TVRO is a term used in North America to refer to the reception of Satellite television from FSS -type satellites 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 22,375 miles (36,000 km) height is a line of sight reception source. A geosynchronous orbit is an Orbit around the Earth with an Orbital period matching the Earth's sidereal rotation period If the satellite is above the horizon, it can be generally received, if it is below the horizon, reception is not possible.

Notable Satellite TVRO UHF TV DX receptions

See also

References

  1. ^ Official WTFDA Club Website - Home
  2. ^ First Live BBC Recording. Federal Standard 1037C, entitled Telecommunications Glossary of Telecommunication Terms is a United States Federal Standard issued by the General Services Administration MW DX, short for Mediumwave DXing, is the hobby of receiving the reception of distant Mediumwave (known as Skywave is the propagation of electromagnetic waves bent (refracted back to the Earth's surface by the Ionosphere. Radio propagation is a term used to explain how Radio waves behave when they are Transmitted, or are propagated from one point on the Earth Alexandra Palace Television Society. Retrieved on April 26, 2005.
  3. ^ FM Broadcasting Chronology. History of American Broadcasting. Retrieved on May 22, 2005.
  4. ^ FM Radio Finds its Niche. R. J. Reiman. Retrieved on May 22, 2005.
  5. ^ George Palmer - Australian TV DX Pioneer. Todd Emslie's TV DX Page. Retrieved on April 26, 2005.
  6. ^ a b Rijn Muntjewerff's 1961-2005 TV DX. Todd Emslie's TV DX Page. Retrieved on August 29, 2005.
  7. ^ http://home.twcny.rr.com/nordquistsyr/FMRECDIS.htm
  8. ^ http://home.twcny.rr.com/nordquistsyr/tvrecdis.htm
  9. ^ Jeff Kruszka's Record-Breaking DTV Tropo
  10. ^ Site no longer available
  11. ^ http://www.etedeschi.ndirect.co.uk/database/it.tv.htm
  12. ^ http://www.wsmb.org/history_of_broadcasting/tv-endnotes.html
  13. ^ Welcome to DX FM
  14. ^ Trans-Atlantic FM 26 June 2003
  15. ^ [1]
  16. ^ [2]
  17. ^ tafm2
  18. ^ Welcome to mcsittel.com
  19. ^ http://www.mcsittel.com/assets/images/wkycdt02.jpg
  20. ^ High Band E Skip. Mike's TV and FM DX Page. Retrieved on April 26, 2005.
  21. ^ http://www.mcsittel.com/assets/images/kvbcdt02.jpg
  22. ^ KVBC-DT-2 and WKYC-DT-2 via Es/My DTV DX
  23. ^ KBEJ-2 via Es
  24. ^ Short Eskip
  25. ^ Anthony (Tony) Mann's TVDX page. The University of Western Australia School of Physics. Retrieved on April 26, 2005.
  26. ^ Todd Emslie's TV FM DX Site
  27. ^ Darwin, Australia VHF DXpedition. Todd Emslie's TV DX Page. Retrieved on April 26, 2005.
  28. ^ Space&Beyond: Moonbounce Advances the State of the Radio Art. ARRL, the national association for Amateur Radio. Retrieved on May 5, 2005.
  29. ^ K3PGP - Experimenters Corner - K3PGP UHF TV reception via EME (1970)
  30. ^ Eavesdropping Mode and Radio Leakage from Earth. NASA CP-2156 Life In The Universe. Retrieved on April 26, 2005.
  31. ^ UHF TV carrier detection by moonbounce (EME)
  32. ^ RWT and the History of TVRO. Real-World Technology Ltd. Retrieved on April 26, 2005.
  33. ^ Amateur radio page of Ian Roberts, ZS6BTE. QSL. net. Retrieved on April 26, 2005.

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