F2 propagation
Encyclopedia
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
Solar cycle
The solar cycle, or the solar magnetic activity cycle, is a periodic change in the amount of irradiation from the Sun that is experienced on Earth. It has a period of about 11 years, and is one component of solar variation, the other being aperiodic fluctuations. Solar variation causes changes in...
of approximately 11 years. During this period, sunspot activity rises to a peak and gradually falls again to a low level. When sunspot
Sunspot
Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature....
activity increases, the reflecting capabilities of the F1 layer surrounding earth enable high frequency short-wave communications. The highest-reflecting layer, the F2 layer, which is approximately 200 miles (320 km) above earth, receives ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiation from the sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, causing ionisation of the gases within this layer. During the daytime when sunspot activity is at a maximum, the F2 layer can become intensely ionized due to radiation from the sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. 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 as well as VHF amateur radio paths. A rising MUF will initially affect the 27 MHz CB
Citizens' band radio
Citizens' Band radio is, in many countries, a system of short-distance radio communications between individuals on a selection of 40 channels within the 27-MHz band. Citizens' Band is distinct from the FRS, GMRS, MURS and amateur radio...
band, and the amateur 28 MHz 10 meters
10 meters
The 10-metre band is a portion of the shortwave radio spectrum internationally allocated to amateur radio and amateur satellite use on a primary basis. The band consists of frequencies stretching from 28000 to 29700 kHz.-History:...
band before reaching 45-55 MHz TV and the 6 Meter amateur band. 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
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...
band. Less frequently, television and amateur 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 TV 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
- In 1958, the FM broadcast radio DX record was set by DXer Gordon Simkin in southern CaliforniaSouthern CaliforniaSouthern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...
when he logged a 45 MHz commercial FM station from KoreaKoreaKorea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
via trans-Pacific F2 propagation at a distance of 5,000 miles (8,000 km). - In October 1979, Anthony Mann (Perth, Western AustraliaPerth, Western AustraliaPerth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....
) received 48.25 MHz audio and 51.75 MHz video from the Holme MossHolme MossHolme Moss is a moor in the south Pennines of England, on the border between the High Peak District of Derbyshire and the West Yorkshire district of Kirklees. It is just inside the boundary of the Peak District National Park....
BBC channel B2 television transmitter. This F2 reception is a world record for reception from a BBC 405-line channel B2 transmitter. - During October to December 1979, United Kingdom DXers Roger Bunney (Hampshire, UK), Hugh Cocks (Sussex, UK), Mike Allmark (Leeds, UK), and Ray Davies (Norwich, UK) all received viewable television pictures from Australian channel TVQ 0TVQ-10TVQ is the Brisbane television station of Network Ten in Australia.The channel was allocated channel 0 on the VHF band and was launched on 1 July 1965 as TVQ-0...
BrisbaneBrisbaneBrisbane is the capital and most populous city in the Australian state of Queensland and the third most populous city in Australia. Brisbane's metropolitan area has a population of over 2 million, and the South East Queensland urban conurbation, centred around Brisbane, encompasses a population of...
(46.26 MHz) via multi-hop F2 propagation. - On January 31, 1981, Todd Emslie, Sydney, Australia, received 41.5 MHz channel B1 television audio transmitted from Crystal Palace TransmitterCrystal Palace TransmitterThe Crystal Palace transmitting station is a broadcasting and telecommunications site in the Crystal Palace area of the London Borough of Bromley, England .Its tower is the third-tallest structure in London...
by the BBCBBCThe 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...
's televisionTelevisionTelevision is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
service, 10,560 miles (16,990 km) away. This BBC B1 reception was also recorded on to audio tape.
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...
- clear-channel station
External links
- TV/FM Antenna Locator
- Worldwide TV/FM DX Association
- Worldwide TV/FM DX Association Forums
- Band 1 TVDX from Europe, North African and Middle East FMDX database
- British FM & TV Circle, 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
- fmdxITALY Home of FM & TV DX in Italy
- 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