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					Amateur Radio
• Amateur radio, often called ham radio, is both a hobby
  and a service in which participants, called "hams," use
  various types of radio communications equipment to
  communicate with other radio amateurs for public
  service, recreation and self-training.
• Amateur radio operators enjoy personal (and often
  worldwide) wireless communications with each other and
  are able to support their communities with emergency
  and disaster communications if necessary, while
  increasing their personal knowledge of electronics and
  radio theory. An estimated six million people throughout
  the world are regularly involved with amateur radio
• The term "amateur" is not a reflection on the skills of the
  participants, which are often quite advanced; rather,
  "amateur" indicates that amateur communications are
  not allowed to be made for commercial or money-making
  purposes
                  History
• Though its origins can be traced to at least
  the late 1800s, amateur radio, as practiced
  today, did not begin until the early 1900s.
  The first listing of amateur radio stations is
  contained in the First Annual Official
  Wireless Blue Book of the Wireless
  Association of America in 1909
      Activities and Practices
• Amateur Radio operators use various
  modes of transmission to communicate.
  Voice transmissions are most
  common, with some, such as frequency
  modulation (FM) offering high quality
  audio, and others, such as single sideband
  (SSB) offering more reliable
  communications when signals are
  marginal and bandwidth is restricted, at
  the sacrifice of audio quality
              Side Bands
• In radio communications, a sideband is a
  band of frequencies higher than or lower
  than the carrier frequency, containing
  power as a result of the modulation
  process. The sidebands consist of all the
  Fourier components of the modulated
  signal except the carrier. All forms of
  modulation produce sidebands
                    SSB
• Single-sideband modulation (SSB) is a
  refinement of amplitude modulation that
  more efficiently uses electrical power and
  bandwidth. It is closely related to vestigial
  sideband modulation (VSB)
      Vestigial sideband (VSB)
• A vestigial sideband (in radio communication)
  is a sideband that has been only partly cut off or
  suppressed. Television broadcasts (in analog
  video formats) use this method if the video is
  transmitted in AM, due to the large bandwidth
  used. It may also be used in digital transmission,
  such as the ATSC standardized 8-VSB. The
  Milgo 4400/48 modem (circa 1967) used
  vestigial sideband and phase-shift keying to
  provide 4800-bit/s transmission over a 1600 Hz
  channel
              Morse Code
• Morse code is a type of character
  encoding that transmits telegraphic
  information using rhythm. Morse code
  uses a standardized sequence of short
  and long elements to represent the
  letters, numerals, punctuation and special
  characters of a given message.
             Contd activities
• Radiotelegraphy using Morse code is an activity
  dating to the earliest days of radio. Even though
  having been largely replaced in commercial and
  military applications by computer-based modes
  and no longer part of most national licensing
  exams for amateur radio, many amateur radio
  operators still enjoy using the CW mode,
  particularly on the shortwave bands and for
  experimental work such as earth-moon-earth
  communication, with its inherent signal-to-noise
  ratio advantages.
            Continuous wave

• A continuous wave or continuous waveform
  (CW) is an electromagnetic wave of constant
  amplitude and frequency; and in mathematical
  analysis, of infinite duration. Continuous wave is
  also the name given to an early method of radio
  transmission, in which a carrier wave is switched
  on and off. Information is carried in the varying
  duration of the on and off periods of the signal.
  In radio transmission, CW waves are also known
  as "undamped waves", to distinguish this
  method from damped wave transmission.
               Radioteletype

• Radioteletype (RTTY) is a telecommunications
  system consisting of two or more teleprinters
  using radio as the transmission medium.
• The term radioteletype is used to describe:
• either the entire family of systems connecting
  two or more teleprinters over radio, regardless of
  alphabet, link system or modulation,
• or specifically the original radioteletype
  system, sometime described as "Baudot".
             Baudot code

• The Baudot code, invented by Émile
  Baudot[1], is a character set predating
  EBCDIC and ASCII. It was the
  predecessor to the International Telegraph
  Alphabet No 2 (ITA2), the teleprinter code
  in use until the advent of ASCII. Each
  character in the alphabet is represented by
  a series of bits, sent over a communication
  channel such as a telegraph wire or a
  radio signal.
                 RY (test signal)

• RYRYRYRY... is a character string that was widely used
  to test a five-level teleprinter or RTTY channel. The
  characters R and Y are "01010" and "10101" in 5-bit
  ITA2 code, also known as Baudot. Thus they are
  Boolean complements of each other. Switching between
  the two characters is a stressful test for
  electromechanical teleprinters. Repeated over and over,
  RYRYRYRY... outputs a carrier wave that regularly and
  rapidly shifts back and forth in frequency. It also provided
  a test for signal polarity; if polarity was reversed, the test
  signal would print as "SG".
• The corresponding string of complementary characters
  in 7-bit ASCII is U*U*U*U*...
                 Damped wave

• A damped wave is an electromagnetic wave whose
  amplitude of oscillation decreases with time, eventually
  going to zero. This term also refers to an early method of
  radio transmission from spark gap transmitters, or other
  types of transmitters having characteristic decrement
  similar to spark transmitters, in which a carrier wave is
  switched on and off. This is generally referred to as
  "Class B" emission. Information is carried in the rhythm
  and spacing with which the signal is sent. Damped
  waves were used for a form of on-off keying (OOK).
  However, such transmitters were noisy and generated a
  wide emission bandwidth.
• There is currently an international prohibition against the
  use of Class B, damped wave emission.
• Hams led the development of packet radio, which has
  employed protocols such as TCP/IP since the 1970s.
  Specialized digital modes such as PSK31 allow real-
  time, low-power communications on the shortwave
  bands. Echolink using Voice over IP technology has
  enabled amateurs to communicate through local
  Internet-connected repeaters and radio nodes[12], while
  IRLP has allowed the linking of repeaters to provide
  greater coverage area. Automatic link establishment
  (ALE) has enabled continuous amateur radio networks to
  operate on the high frequency bands with global
  coverage.
• Fast scan amateur television has gained popularity as
  hobbyists adapt inexpensive consumer video electronics
  like camcorders and video cards in home computers.
  Because of the wide bandwidth and stable signals
  required, amateur television is typically found in the
  70 cm (420 MHz–450 MHz) frequency range, though
  there is also limited use on 33 cm (902 MHz–928 MHz),
  23 cm (1240 MHz–1300 MHz) and higher. These
  requirements also effectively limit the signal range to
  between 20 and 60 miles (30 km–100 km), however, the
  use of linked repeater systems can allow transmissions
  across hundreds of miles.
• These repeaters, or automated relay stations, are used
  on VHF and higher frequencies to increase signal range.
  Repeaters are usually located on top of a mountain, hill
  or tall building, and allow operators to communicate over
  hundreds of square miles using a low power hand-held
  transceiver. Repeaters can also be linked together by
  use of other amateur radio bands, landline or the Internet
• Amateur radio operators use their amateur radio
  station to make contacts with individual hams as
  well as participating in round table discussion
  groups or "rag chew sessions" on the air. Some
  join in regularly scheduled on-air meetings with
  other amateur radio operators, called "Nets" (as
  in "networks") which are moderated by a station
  referred to as "Net Control". Nets can allow
  operators to learn procedures for emergencies,
  be an informal round table or be topical,
  covering specific interests shared by a group.
                    Licensing
• In all countries, amateur radio operators are required to
  pass a licensing exam displaying knowledge and
  understanding of key concept. In response, hams are
  granted operating privileges in larger segments of the
  radio frequency spectrum using a wide variety of
  communication techniques with higher power levels
  permitted. This practice is in contrast to unlicensed
  personal radio services such as CB radio, Multi-Use
  Radio Service, or Family Radio Service/PMR446 that
  require type-approved equipment restricted in frequency
  range and power.
• In many countries, amateur licensing is a routine
  civil administrative matter. Amateurs are
  required to pass an examination to demonstrate
  technical knowledge, operating competence and
  awareness of legal and regulatory requirements
  in order to avoid interference with other
  amateurs and other radio services. There are
  often a series of exams available, each
  progressively more challenging and granting
  more privileges in terms of frequency availability,
  power output, permitted experimentation, and in
  some countries, distinctive callsigns.
• Amateur radio licensing in the United States
  serves as an example of the way some countries
  award different levels of amateur radio licenses
  based on technical knowledge.
• Three sequential levels of licensing exams
  (Technician Class, General Class and Amateur
  Extra Class) are currently offered, which allow
  operators who pass them access to larger
  portions of the Amateur Radio spectrum and
  more desirable callsigns.
              Newcomers

Join this by
• by finding a local club
• often study independently by purchasing
  books or other materials
• sometimes with the help of a mentor,
  teacher or friend
• Established amateurs who help
  newcomers are often referred to as
  "Elmers" within the ham community
                    Callsign

• In broadcasting and radio communications, a
  call sign (also known as a callsign, callname
  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
                  Callsigns
• Upon licensing, a radio amateur's national
  government issues a unique callsign to the radio
  amateur. The holder of a callsign uses it on the
  air to legally identify the operator or station
  during any and all radio communication
• In certain jurisdictions, an operator may also
  select a "vanity" callsign although these must
  also conform to the issuing government's
  allocation and structure used for Amateur Radio
  callsigns
• Sometime fee is to be paid as in US to obtain
  callsigns
              Callsign structure
•  Callsign structure as prescribed by the ITU, consists of
  three parts which break down as follows, using the
  callsign ZS1NAT as an example:
• ZS – Shows the country from which the callsign
  originates and may also indicate the license class. (This
  callsign is licensed in South Africa, and is CEPT Class
  1).
• 1 – Gives the subdivision of the country or territory
  indicated in the first part (this one refers to the Western
  Cape).
• NAT – The final part is specific to the holder of the
  license, identifying that person specifically.
• Many countries do not follow the ITU
  convention for the numeral. In the United
  Kingdom the calls G2xxx, G3xxx, and
  G6xx may be issued to stations that are
  geographically right next to each other
                  Privileges

• Unlike other RF spectrum users, radio amateurs
  may build or modify transmitting equipment for
  their own use within the amateur spectrum
  without the need to obtain government
  certification of the equipment
• Licensed amateurs can also use any frequency
  in their bands (rather than being allocated fixed
  frequencies or channels) and can operate
  medium to high-powered equipment on a wide
  range of frequencies
• Although allowable power levels are moderate by
  commercial standards, they are sufficient to enable
  global communication. Power limits vary from country to
  country and between license classes within a country.
  For example, the power limits for the highest available
  license classes in a few selected countries are: 2.25 kW
  in Canada, was 2 kW in the former Yugoslavia, 1.5 kW in
  the United States, 1 kW in Belgium and Switzerland, 750
  W in Germany, 500 W in Italy, 400 W in Australia, India
  and the United Kingdom, and 150 W in Oman.
• When traveling abroad, visiting amateur operators must
  follow the rules of the country in which they wish to
  operate
    Band plans and frequency
           allocations
• In Trinidad and Tobago, hams are allowed
  to use a repeater which is located on
  148.800 MHz.
• In Australia and New Zealand ham
  operators are authorized to use one of the
  UHF TV channels
• Alaska statewide emergency frequency of
  5167.5 kHz.

				
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