Amateur radio license

An amateur radio license is a legal document or permit giving official permission to the license holder to operate an amateur radio station. The license typically permits the bearer to transmit a signal on designated radio frequencies in order to conduct two-way communications with other licensed stations. In some countries, an amateur radio license is necessary in order to purchase or possess amateur radio equipment. Amateur radio licenses are issued by governmental authorities, in the USA it’s the Federal Communications Commission FCC. An amateur radio license is only valid in the country in which it is issued, or in another country that has a reciprocal licensing agreement with the issuing country.

Both the requirements for and privileges granted to a licensee vary from country to country, but generally follow the international regulations and standards established by the International Telecommunications Union and World Radio Conferences. Most governments issue several different classes of license, usually structured to grant additional privileges to those who demonstrate additional knowledge and proficiency.

An individual granted an amateur radio license is referred to as an amateur radio operator. In most countries, an individual will be assigned a call sign with their license. In some countries, a separate "station license" is required for any station used by an amateur radio operator. Amateur radio licenses may also be granted to organizations or clubs.

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Amateur radio operator

An amateur radio operator is an individual who has been assigned an amateur radio license by a Federal Communications Commission FCC. An amateur radio operator uses the equipment at an amateur radio station to engage in two-way personal communications with other similarly licensed individuals using radio frequencies assigned to the Amateur Radio Service. As a condition of their license, most amateur radio operators are assigned a call sign that they use to identify themselves during communication. There are about three million amateur radio operators worldwide.

Amateur radio operators are also known as radio amateurs or hams. The origin of the term "ham", as a synonym for an amateur radio operator, was a taunt by professional operators. An amateur radio operator who has died is referred to by other amateur radio operators as a "silent key".

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Amateur radio station
 
An amateur radio station is a facility equipped with the apparatus necessary for carrying on radio communications in the Amateur Radio Service. There are several types of amateur radio stations: an amateur radio station may be located in a building, installed in a vehicle, located in space, or established in a temporary field location. Each station is operated by an amateur radio operator and is identified by a call sign issued by the authorized regulatory authority of the country in which it is located.

A slang term for the location of radio equipment is the "shack" after the small enclosures added to the upper works of ships to hold the first radio equipment and their batteries.

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Amateur radio

Amateur radio, often called Ham radio, is a hobby enjoyed by about six million people throughout the world. An amateur radio operator, also known as a ham or radio amateur, uses advanced radio equipment to communicate with other radio amateurs for public service, recreation and self-training.

Amateur radio operators have personal wireless communications with friends, family members, and even complete strangers, and often support their communities with emergency and disaster communications while increasing their personal knowledge of electronics and radio theory.

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Antenna

An antenna or aerial is a transducer designed to transmit or receive radio waves which are a class of electromagnetic waves. In other words, antennas convert radio frequency electrical currents into electromagnetic waves and vice versa. Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless lan, radar, and space exploration. Antennas usually work in air or outer space, but can also be operated under water or even through soil and rock at certain frequencies for short distances.

Physically, an antenna is an arrangement of conductors that generate a radiating electromagnetic field in response to an applied alternating voltage and the associated alternating electric current, or can be placed in an electromagnetic field so that the field will induce an alternating current in the antenna and a voltage between its terminals. Some antenna devices (parabola, horn antenna) just adapt the free space to another type of antenna.

Antennas were used in 1888 by Heinrich Hertz (1857-1894) to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. He even placed the emitter dipole in the focal point of a parabolic reflector.

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Call sign
 
In broadcasting and radio communications, a call sign (also known as a callsign or call letters, or abbreviated as a call) is a unique designation for a transmitting station. In some countries they are used as names for broadcasting stations, but in many other countries they are not. A call sign can be formally assigned by a government agency, informally adopted by individuals or organizations, or even cryptographically encoded to disguise a station's identity.

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Ham Origin

Ham is an informal term for an amateur radio operator, and, by extension, "ham radio" refers to amateur radio in general. This use of the word first appeared in the United States during the opening decade of the twentieth century — for example, Robert A. Morton in "Wireless Interference", from the April, 1909 Electrician and Mechanic, reported overhearing an amateur radio transmission which included the comment: "Say, do you know the fellow who is putting up a new station out your way? I think he is a ham." However, the term did not gain widespread usage in the United States until around 1920, after which it slowly spread to other English-speaking countries.

In spite of — or perhaps because of — its relatively straight-forward origin, many interesting and colorful folk etymologies about the supposed origin of "ham" have been developed over the years. Below are some of the competing later explanations that are often charming, but also wrong.

Ham-Fisted - One alternate explanation is that "ham" is a shortened version of "ham-fisted", meaning clumsy. This is a reasonable conjecture, given that all early amateur radio stations used hand-operated telegraph keys to transmit Morse code, and sending style is referred to as an operator's "fist", so someone who sends badly could be called ham-fisted. But the earliest references to "ham" use only the single word, and there is no evidence that it evolved as a truncation of a longer phrase.

"A little station called HAM" - This widely circulated but fanciful tale claims that, circa 1911, an impassioned speech made by Harvard University student Albert Hyman to the United States Congress, in support of amateur radio operators, turned the tide and helped defeat a bill that would have ended amateur radio activity entirely, by assigning the entire radio spectrum over to the military. An amateur station that Hyman supposedly shared with two others (Bob Almy and Peggie Murray), which was said to be using the self-assigned call sign "HAM" (short for Hyman-Almy-Murray), thus came to represent all of amateur radio. However, this story apparently first surfaced in 1948, and virtually none of the "facts" in the account actually check out, including whether "a little station called HAM" ever really existed.

"Home Amateur Mechanic" magazine - In this version, supposedly HAM was derived from the initials of a "very popular" magazine which covered radio extensively. But there is no evidence that there ever was a magazine by this name.

Hertz-Armstrong-Marconi - It is sometimes claimed that HAM came from the first letter from the last names of three radio pioneers: Heinrich Rudolf Hertz, Edwin Armstrong, and Guglielmo Marconi. However, this cannot be the source of the term as Armstrong was an unknown college student when the term first appeared.

Hammarlund legend - Likely an example of corporate wishful thinking, Hammarlund products were supposedly so pre-eminent in the pioneering era of radio that they became a part of the language of radio. As the story goes, early radio enthusiasts affectionately referred to Hammarlund products as "Ham" products, and called themselves "Ham" operators. In truth, Hammarlund was a minor and barely known company at the time "ham" started to be used.

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Morse code

Morse code is a method for transmitting telegraphic information, using standardized sequences of short and long elements to represent the letters, numerals, punctuation and special characters of a message. The short and long elements can be formed by sounds, marks or pulses, and are commonly known as "dots" and "dashes" or "dits" and "dahs".

International Morse code is composed of six elements:

short mark, dot or 'dit' (·)
longer mark, dash or 'dah' (-)
intra-character gap (between the dots and dashes within a character)
short gap (between letters)
medium gap (between words)
long gap (between sentences — about seven units of time)

These six elements serve as the basis for International Morse code and therefore can be applied to the use of Morse code world-wide.

Morse code can be transmitted in a number of ways: originally as electrical pulses along a telegraph wire, but also as an audio tone, as a radio signal with short and long pulses or tones, or as a mechanical or visual signal (e.g. a flashing light) using devices like an Aldis lamp or a heliograph. Morse code is transmitted using just two states — on and off — so it was an early form of a digital code. However, it is technically not binary, as the pause lengths are required to decode the information.

Originally created for Samuel F. B. Morse's electric telegraph in the early 1840s, Morse code was also extensively used for early radio communication beginning in the 1890s. For the first half of the twentieth century, the majority of high-speed international communication was conducted in Morse code, using telegraph lines, undersea cables, and radio circuits. However, the variable length of the Morse characters made it hard to adapt to automated circuits, so for most electronic communication it has been replaced by more machinable formats, such as Baudot code and ASCII.

The most popular current use of Morse code is by amateur radio operators, although no longer a requirement for Amateur licensing in most countries, it also continues to be used for specialized purposes, including identification of navigational radio beacon and land mobile transmitters, plus some military communication, including flashing-light semaphore communications between ships in some naval services. Morse code is the only digital modulation mode designed to be easily read by humans without a computer, making it appropriate for sending automated digital data in voice channels, as well as making it ideal for emergency signaling, such as by way of improvised energy sources that can be easily "keyed" such as by supplying and removing electric power (e.g. by switching a breaker on and off).

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Radio propagation

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 to another.

In free space, all electromagnetic waves (radio, light, X-rays, etc) obey the inverse-square law which states that the power density of an electromagnetic wave is proportional to the inverse of the square of "r" (where "r" is the distance [range] from the source) or:

Power Density = 1 / {r^2}.
Doubling the distance from a transmitter means that the power density of the radiated wave at that new location is reduced to one-quarter of its previous value.

The far-field magnitudes of the electric and magnetic field components of electromagnetic radiation are equal, and their field strengths are inversely proportional to distance. Doubling the propagation path distance from the transmitter reduces their received field strengths by one-half. The reduction of each of these fields by one-half is the result of the power density reduction to one-quarter over that doubled path length.

Electromagnetic wave propagation is also affected by several other factors determined by its path from point to point. This path can be a direct line of sight path or an over-the-horizon path aided by refraction in the ionosphere.

Lower frequencies (between 30 and 3,000 kHz) have the property of following the curvature of the earth via groundwave propagation in the majority of occurrences. The interaction of radio waves with the ionized regions of the atmosphere makes radio propagation more complex to predict and analyze than in free space. Ionospheric radio propagation has a strong connection to space weather.

Since radio propagation is somewhat unpredictable, such services as emergency locator transmitters, in-flight communication with ocean-crossing aircraft, and some television broadcasting have been moved to satellite transmitters. A satellite link, though expensive, can offer highly predictable and stable line of sight coverage of a given area (see Goggle Maps for a "real-world" application").

A sudden ionospheric disturbance is often the result of large solar flares directed at Earth. These solar flares can disrupt HF radio propagation and affect GPS accuracy.

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Radio

Radio is the wireless transmission of signals, by modulation of electromagnetic waves with frequencies below those of visible light.

Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. It does not require a medium of transport. Information is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude or their frequency. When radio waves pass an electrical conductor, the oscillating fields induce an alternating current in the conductor. This can be detected and transformed into sound or other signals that carry information.

The word 'radio' is used to describe this phenomenon, and radio transmissions are classed as radio frequency emissions.

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Receiver

In radio terminology, a receiver is an electronic circuit that receives a radio signal from an antenna and converts the signal into sound, pictures, navigational-position information, etc. Radio and radio receiver are often used specifically for receivers whose output consists only of sound, although other types of receivers, such as television receivers, are technically radio receivers as well.

As an audio appliance, "receiver" refers to a tuner, a preamplifier, and a power amplifier all on the same chassis. Audiophiles will refer to such a device as an integrated receiver, while a single chassis that implements only one of the three component functions is called a discrete component. Some audio purists still prefer three discreet units - tuner, preamplifier and power amplifier - but the integrated receiver has, for some years, been the mainstream choice for listening.

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Silent key

Silent key refers to an amateur radio operator who is deceased. The term is frequently abbreviated SK. The key in the term refers to a telegraph key, the instrument that all early amateur radio operators, as well as many contemporary amateur radio operators, have used to send Morse code. The term SK is used to refer to any amateur radio operator who is deceased, regardless of whether or not they were known to have actively used a telegraph key or Morse code in their two-way personal communications.

When transmitted as two Morse code characters without separating audio delay, SK is a Morse code prosign meaning "end of communications", from the phrase "Stop Keying".

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Telegraphy

Telegraphy (from the Greek words tele = far and graphein = write) is the long-distance transmission of written messages without physical transport of letters, originally by changing something that could be observed from a distance (optical telegraphy). Radiotelegraphy or wireless telegraphy transmits messages using radio. Telegraphy includes recent forms of data transmission such as fax, email, and computer networks in general. (A telegraph is a machine for transmitting and receiving messages over long distances, i.e. for telegraphy. The word telegraph alone generally refers to an electrical telegraph). Wireless telegraphy is also known as CW, for continuous wave (a carrier modulated by on-off keying, as opposed to the earlier radio technique using a spark gap).

Telegraphy messages sent by the telegraph operators using Morse code were known as telegrams or cablegrams, often shortened to a cable or a wire message. Later, telegrams sent by the Telex network, a switched network of teleprinters similar to the telephone network, were known as telex messages. Before long distance telephone services were readily available or affordable, telegram services were very popular. Telegrams were often used to confirm business dealings and, unlike e-mail, telegrams were commonly used to create binding legal documents for business dealings.

Wire picture or wire photo was a newspaper picture that was sent from a remote location by a facsimile telegraph.

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Transceiver

A transceiver is a device that has both a transmitter and a receiver which are combined and share common circuitry or a single housing. If no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s. Technically, transceivers must combine a significant amount of the transmitter and receiver handling circuitry. Similar devices include transponders, transverters, and repeaters.

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Transmission

In telecommunications, transmission is the act of transmitting electrical messages (and the associated phenomena of radiant energy that passes through media). Messages can be a series of data units, such as binary digits, or groups of those, variously called frames, blocks.

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Transmitter
 
A transmitter (sometimes abbreviated XMTR) is an electronic device which with the aid of an antenna propagates an electromagnetic signal such as radio, television, or other telecommunications.

A transmitter usually has a power supply, an oscillator, a modulator, and amplifiers for audio frequency (AF) and radio frequency (RF). The modulator is the device which piggybacks (or modulates) the signal information onto the carrier frequency, which is then broadcast. Sometimes a device (for example, a cell phone) contains both a transmitter and a radio receiver, with the combined unit referred to as a transceiver.

More generally and in communications and information processing, a "transmitter" is any object (source) which sends information to an observer (receiver). When used in this more general sense, vocal cords may also be considered an example of a "transmitter".

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Tuner

A tuner is an adjustable device which passes one radio frequency, or band of frequencies, and excludes others, by using electrical resonance. The simplest tuner consists of an inductor and capacitor. Combined with a detector, also known as a demodulator, it becomes the simplest radio receiver, often called a crystal set.

Tuners can be either stereo or mono, and are available for TV, FM, and AM signals.

Typically, AM and FM tuners are sold with built-in amplifiers and/or loudspeakers, and this device is referred to as a receiver.

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