Radioteletype (RTTY) is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations connected by radio rather than a wired link. Radioteletype evolved from earlier landline teleprinter operations that began in the mid-1800s. The US Navy Department successfully tested printing telegraphy between an airplane and ground radio station in 1922. Later that year, the Radio Corporation of America successfully tested printing telegraphy via their Chatham, Massachusetts, radio station to the R.M.S. Majestic. Commercial RTTY systems were in active service between San Francisco and Honolulu as early as April 1932 and between San Francisco and New York City by 1934. The US military used radioteletype in the 1930s and expanded this usage during World War II. From the 1980s, teleprinters were replaced by personal computers (PCs) running software to emulate teleprinters.
Wireless telegraphy or radiotelegraphy is transmission of text messages by radio waves, analogous to electrical telegraphy using cables. Before about 1910, the term wireless telegraphy was also used for other experimental technologies for transmitting telegraph signals without wires. In radiotelegraphy, information is transmitted by pulses of radio waves of two different lengths called "dots" and "dashes", which spell out text messages, usually in Morse code. In a manual system, the sending operator taps on a switch called a telegraph key which turns the transmitter on and off, producing the pulses of radio waves. At the receiver the pulses are audible in the receiver's speaker as beeps, which are translated back to text by an operator who knows Morse code.
The Q-code is a standardised collection of three-letter codes that each start with the letter "Q". It is an operating signal initially developed for commercial radiotelegraph communication and later adopted by other radio services, especially amateur radio. To distinguish the use of a Q-code transmitted as a question from the same Q-code transmitted as a statement, operators either prefixed it with the military network question marker "INT" or suffixed it with the standard Morse question mark UD.
SOS is a Morse code distress signal, used internationally, originally established for maritime use. In formal notation SOS is written with an overscore line, to indicate that the Morse code equivalents for the individual letters of "SOS" are transmitted as an unbroken sequence of three dots / three dashes / three dots, with no spaces between the letters. In International Morse Code three dots form the letter "S" and three dashes make the letter "O", so "S O S" became a common way to remember the order of the dots and dashes. IWB, VZE, 3B, and V7 form equivalent sequences, but traditionally SOS is the easiest to remember.
CQD is one of the first distress signals adopted for radio use. On 7 January 1904 the Marconi International Marine Communication Company issued "Circular 57", which specified that, for the company's installations, beginning 1 February 1904 "the call to be given by ships in distress or in any way requiring assistance shall be 'C Q D' ".
Marine VHF radio is a worldwide system of two way radio transceivers on ships and watercraft used for bidirectional voice communication from ship-to-ship, ship-to-shore, and in certain circumstances ship-to-aircraft. It uses FM channels in the very high frequency (VHF) radio band in the frequency range between 156 and 174 MHz, inclusive, designated by the International Telecommunication Union as the VHF maritime mobile band. In some countries additional channels are used, such as the L and F channels for leisure and fishing vessels in the Nordic countries. Transmitter power is limited to 25 watts, giving them a range of about 100 kilometres.
A coastradio station is an on-shore maritime radio station which monitor radio distress frequencies and relays ship-to-ship and ship-to-land communications.
CQ is a station code used by wireless operators derived from long established telegraphic practice on undersea cables and landlines, particularly used by those communicating in Morse code,, but also by voice operators, to make a general call. Transmitting the letters CQ on a particular radio frequency means that the transmission is a broadcast or "General Call" to anyone listening, and when the operator sends "K" or says "Go Ahead" it is an invitation for any licensed radio station listening on that frequency to respond. Its use on radio matched the existing use on Morse landline telegraphy and dates from the earliest wireless stations. It was widely used in point-to-point diplomatic and press services, maritime, aviation, and police services until those services eliminated Morse radiotelegraphy. It is still widely used in amateur radio which still has active use of Morse radiotelegraphy.
From early in the 20th century, the radio frequency of 500 kilohertz (500 kHz) was an international calling and distress frequency for Morse code maritime communication. For much of its early history, this frequency was referred to by its equivalent wavelength, 600 meters, or, using the earlier frequency unit name, 500 kilocycles or 500 kc.
In broadcasting and radio communications, a call sign is a unique identifier for a transmitter station. 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.
ACP-131 is the controlling publication for the listing of Q codes and Z codes. It is published and revised from time to time by the Combined Communications Electronics Board (CCEB) countries: Australia, New Zealand, Canada, United Kingdom, and United States. When the meanings of the codes contained in ACP-131 are translated into various languages, the codes provide a means of communicating between ships of various nations, such as during a NATO exercise, where there is no common language.
WCC was the busiest coast station in the public ship-to-shore radio service for most of the 20th century.
Arthur Moore was a Welsh wireless pioneer who heard the distress signal from RMS Titanic on his home-made equipment before news of the disaster reached Britain. He subsequently worked for the Marconi Company, helping to develop radio and sonar.
Portishead Radio was a radio station in England that provided worldwide maritime communications and long-range aeronautical communications from 1928 until 2000. It was the world's largest and busiest long-distance HF maritime radio station. In 1974, the station employed 154 radio operators who handled over 20 million words per year. It was originally operated by the General Post Office (GPO), then the Post Office (1969–1981) and subsequently by British Telecom, which was privatised in 1984.
The Massie Wireless Station (PJ) was built in Point Judith, Rhode Island, in 1907 and may be the oldest surviving working wireless station in the world. It is named for inventor Walter Wentworth Massie, president of the Massie Wireless Telegraph Company. The structure was moved to the New England Wireless and Steam Museum in 1983 where it is preserved as a technology museum and historic site.
The Marconi–RCA Wireless Receiving Station is a historic district at the junction of Old Comers Rd. and Orleans Rd. in Chatham, Massachusetts. It and its companion transmitter station at Marion were used for WCC, the busiest ship to shore radio station for most of the 20th century. The district includes eight red brick buildings constructed by Marconi in 1914 to house the station's operations; it was listed on the National Register of Historic Places in 1994, and is now home to the Chatham Marconi Maritime Center museum.
Although they often faced obstacles and policy limitations, beginning in the early 1900s a few women were able to participate in the pioneering development of radio communication.
APRS Calling is a manual procedure for calling stations on the Automatic Packet Reporting System (APRS) to initiate communications on another frequency, or possibly by other means. It is inspired by Digital Selective Calling, a part of the Global Maritime Distress Safety System. It also builds on existing digital procedures inherited from morse code and radioteletype operation. ITU Q codes are used in conjunction with APRS text messages to implement APRS calling. APRS calling is intended to complement monitoring voice calling frequencies.
