VHF in the context of "Broadcast television"

Terrestrial television, or over-the-air television (OTA) is a type of television broadcasting in which the content is transmitted via radio waves from the terrestrial (Earth-based) transmitter of a TV station to a TV receiver having an antenna. The term terrestrial is more common in Europe and Latin America, while in Canada and the United States it is called over-the-air or simply broadcast. This type of TV broadcast is distinguished from newer technologies, such as satellite television (direct broadcast satellite or DBS television), in which the signal is transmitted to the receiver from an overhead satellite; cable television, in which the signal is carried to the receiver through a cable; and Internet Protocol television, in which the signal is received over an Internet stream or on a network utilizing the Internet Protocol. Terrestrial television stations broadcast on television channels with frequencies between about 52 and 600 MHz in the VHF and UHF bands. Since radio waves in these bands travel by line of sight, reception is generally limited by the visual horizon to distances of 64–97 kilometres (40–60 miles), although under better conditions and with tropospheric ducting, signals can sometimes be received hundreds of kilometers distant.

Terrestrial television was the first technology used for television broadcasting. The BBC began broadcasting in 1929 and by 1930 many radio stations had a regular schedule of experimental television programmes. However, these early experimental systems had insufficient picture quality to attract the public, due to their mechanical scan technology, and television did not become widespread until after World War II with the advent of electronic scan television technology. The television broadcasting business followed the model of radio networks, with local television stations in cities and towns affiliated with television networks, either commercial (in the US) or government-controlled (in Europe), which provided content. Television broadcasts were in greyscale (called black and white) until the transition to color television in the 1960s.

An antenna farm, satellite dish farm or dish farm is an area dedicated to television or radio telecommunications transmitting or receiving antenna equipment, such as C, K_u or K_a band satellite dish antennas, UHF/VHF/AM/FM transmitter towers or mobile cell towers. The history of the term "antenna farm" is uncertain, but it dates to at least the 1950s.

In telecom circles, any area with more than three antennas could be referred to as an antenna farm. In the case of an AM broadcasting station (mediumwave and longwave, occasionally shortwave), the multiple mast radiators may all be part of an antenna system for a single station, while for VHF and UHF the site may be under joint management. Alternatively, a single tower with many separate antennas is often called a "candelabra tower".

In radio communication, skywave or skip refers to the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere. Since it is not limited by the curvature of the Earth, skywave propagation can be used to communicate beyond the horizon, at intercontinental distances. It is mostly used in the shortwave frequency bands.

As a result of skywave propagation, a signal from a distant AM broadcasting station, a shortwave station, or – during sporadic E propagation conditions (principally during the summer months in both hemispheres) – a distant VHF FM or TV station can sometimes be received as clearly as local stations. Most long-distance shortwave (high frequency) radio communication – between 3 and 30 MHz – is a result of skywave propagation. Since the early 1920s amateur radio operators (or "hams"), limited to lower transmitter power than broadcast stations, have taken advantage of skywave for long-distance (or "DX") communication.

Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from specific magnetic properties of certain atomic nuclei. High-resolution nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics and crystals as well as non-crystalline materials. NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging (MRI). The original application of NMR to condensed matter physics is nowadays mostly devoted to strongly correlated electron systems. It reveals large many-body couplings by fast broadband detection and should not be confused with solid state NMR, which aims at removing the effect of the same couplings by Magic Angle Spinning techniques.

The most commonly used nuclei are
H and
C, although isotopes of many other elements, such as
F,
P, and
Si, can be studied by high-field NMR spectroscopy as well. In order to interact with the magnetic field in the spectrometer, the nucleus must have an intrinsic angular momentum and nuclear magnetic dipole moment. This occurs when an isotope has a nonzero nuclear spin, meaning an odd number of protons and/or neutrons (see Isotope). Nuclides with even numbers of both have a total spin of zero and are therefore not NMR-active.

TRANSRADIO SenderSysteme Berlin AG was a German radio communication systems producer, specialised in research into and development and design of AM, VHF/FM and DRM as well as military and commercial broadcast systems. For a time, it was a subsidiary of AMPEGON AG, a Swiss company and later an affiliate company of CESTRON International GmbH named Elsyscom GmbH.

In times of crisis and natural disasters, amateur radio is often used as a means of emergency communication when wireline, cell phones and other conventional means of communications fail.

Unlike commercial systems, amateur radio is usually independent of terrestrial facilities that can fail. It is dispersed throughout a community without "choke points" such as cellular telephone sites that can be overloaded.

The Croydon transmitting station is a broadcasting and telecommunications facility on Beaulieu Heights in Upper Norwood, London, England (grid reference TQ332696), in the London Borough of Croydon, owned by Arqiva. It was established in 1955 and initially used a small lattice tower. The present tower is 152 metres (499 ft) high and was built in 1962.

It was originally used to broadcast the London ITV signal on VHF Band III. When UHF broadcasting began, the nearby Crystal Palace transmitting station was used. VHF television was discontinued in 1985, and the Croydon transmitter was not used for regular TV broadcasting until 1997, when a new directional UHF antenna, designed to avoid interference with continental transmitters, was installed to carry the newly launched Channel 5 in the London area. It carried Channel 5's analogue signal, and the digital terrestrial signal is transmitted from Crystal Palace. Croydon also had reserve transmitters for BBC1, BBC2, ITV and Channel 4, but these were used only in the event of engineering works or a failure at Crystal Palace. Since the digital switchover in April 2012 no television has been broadcast from Croydon, but it is still used as a backup for Crystal Palace for the BBC A & B, Digital 3&4 and COM 4, 5 and 6 multiplexes.

Radio modems are modems that transfer data wirelessly across a range of up to tens of kilometres.Using radio modems is a modern way to create Private Radio Networks (PRN). Private radio networks are used in critical industrial applications, when real-time data communication is needed. Radio modems enable users to be independent of telecommunication or satellite network operators. In most cases users use licensed frequencies either in the UHF or VHF bands. In certain areas licensed frequencies may be reserved for a given user, thus ensuring that there is less likelihood of radio interference from other radio frequency transmitters. Also licence free frequencies are available in most countries, enabling easy implementation, but at the same time other users may use the same frequency, thus making it possible that a given frequency is blocked.Typical users for radio modems are: land survey differential GPS, fleet management applications, SCADA applications (utility distribution networks), automated meter reading (AMR), telemetry applications and many more. Since applications usually require high reliability of data transfer and very high uptime, radio performance plays a key role. Factors influencing radio performance are: antenna height and type, the sensitivity of the radio, the output power of the radio and the complete system design.

A vessel traffic service is a marine traffic monitoring system established by harbour or port authorities, similar to air traffic control for aircraft. The International Maritime Organization defines vessel traffic service as "a service implemented by a competent authority designed to improve the safety and efficiency of vessel traffic and protect the environment. The service shall have the capability to interact with the traffic and respond to traffic situations developing in the vessel traffic service area". Typical vessel traffic service systems use radar, closed-circuit television, VHF radiotelephony and automatic identification system to keep track of vessel movements and provide navigational safety in a limited geographical area.

In the United States, vessel traffic services are established and operated by the Coast Guard Navigation Center. Some services operate as partnerships between the Coast Guard and private agencies.