Radioteletype (RTTY) is a
telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
s system consisting originally of two or more
electromechanical
In engineering, electromechanics combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems ...
teleprinter
A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...
s in different locations connected by
radio
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...
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
Chatham () is a town in Barnstable County, Massachusetts, United States. Chatham is located at the southeast tip of Cape Cod and has historically been a fishing community. First settled by the English in 1664, the township was originally called Mo ...
, radio station to the R.M.S. Majestic. Commercial RTTY systems were in active service between
San Francisco
San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...
and
Honolulu
Honolulu (; ) is the capital and largest city of the U.S. state of Hawaii, which is in the Pacific Ocean. It is an unincorporated county seat of the consolidated City and County of Honolulu, situated along the southeast coast of the island ...
as early as April 1932 and between San Francisco and
New York City
New York, often called New York City or NYC, is the List of United States cities by population, most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the L ...
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 computer
A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...
s (PCs) running
software to emulate teleprinters.
The term radioteletype is used to describe both the original radioteletype system, sometimes described as "
Baudot", as well as the entire family of systems connecting two or more teleprinters or PCs using software to emulate teleprinters, over radio, regardless of alphabet, link system or modulation.
In some applications, notably military and government, radioteletype is known by the acronym RATT (Radio Automatic Teletype).
History
![HAL3100](https://upload.wikimedia.org/wikipedia/commons/a/a3/HAL3100.jpg)
Landline teleprinter operations began in 1849 when a circuit was put in service between
Philadelphia
Philadelphia, often called Philly, is the largest city in the Commonwealth of Pennsylvania, the sixth-largest city in the U.S., the second-largest city in both the Northeast megalopolis and Mid-Atlantic regions after New York City. Sinc ...
and New York City.
Émile Baudot
Jean-Maurice-Émile Baudot (; 11 September 1845 – 28 March 1903), French telegraph engineer and inventor of the first means of digital communication Baudot code, was one of the pioneers of telecommunications. He invented a multiplexed printi ...
designed a system using a five unit code in 1874 that is still in use today. Teleprinter system design was gradually improved until, at the beginning of World War II, it represented the principal distribution method used by the news services.
Radioteletype evolved from these earlier landline teleprinter operations. The
US Department of the Navy
The United States Department of the Navy (DoN) is one of the three military departments within the Department of Defense of the United States of America. It was established by an Act of Congress on 30 April 1798, at the urging of Secretary o ...
successfully tested printing telegraphy between an airplane and ground radio station in August 1922. Later that year, the Radio Corporation of America successfully tested printing telegraphy via their Chatham, MA radio station to the
RMS ''Majestic''. An early implementation of the Radioteletype was the Watsongraph, named after
Detroit
Detroit ( , ; , ) is the largest city in the U.S. state of Michigan. It is also the largest U.S. city on the United States–Canada border, and the seat of government of Wayne County. The City of Detroit had a population of 639,111 at th ...
inventor Glenn Watson in March 1931. 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. The Navy called radioteletype ''RATT'' (Radio Automatic Teletype) and the Army Signal Corps called radioteletype ''SCRT'', an abbreviation of Single-Channel Radio Teletype. The military used frequency shift keying technology and this technology proved very reliable even over long distances.
From the 1980s, teleprinters were replaced by computers running teleprinter emulation software.
Technical description
A radioteletype station consists of three distinct parts: the Teletype or
teleprinter
A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...
, the
modem
A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ...
and the
radio
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...
.
The Teletype or teleprinter is an
electromechanical
In engineering, electromechanics combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems ...
or
electronic
Electronic may refer to:
*Electronics, the science of how to control electric energy in semiconductor
* ''Electronics'' (magazine), a defunct American trade journal
*Electronic storage, the storage of data using an electronic device
*Electronic co ...
device. The word ''Teletype'' was a trademark of the Teletype Corporation, so the terms "TTY", "RTTY", "RATT" and "teleprinter" are usually used to describe a generic device without reference to a particular manufacturer.
Electromechanical teleprinters are heavy, complex and noisy, and have largely been replaced with electronic units. The teleprinter includes a keyboard, which is the main means of entering text, and a printer or
visual display unit
A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls.
The d ...
(VDU). An alternative input device is a
perforated tape reader and, more recently, computer
storage media
Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are consi ...
(such as floppy disks). Alternative output devices are tape perforators and computer storage media.
The line output of a teleprinter can be at either
digital logic
A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more Binary number, binary inputs that produces a single binary output. Depending on the context, the term may refer to an id ...
levels (+5 V signifies a logical "1" or ''mark'' and 0 V signifies a logical "0" or ''space'') or
line level
Line level is the specified strength of an audio signal used to transmit analog audio between components such as CD and DVD players, television sets, audio amplifiers, and mixing consoles.
Line level sits between other levels of audio signal ...
s (−80 V signifies a "1" and +80 V a "0"). When no traffic is passed, the line idles at the "mark" state.
When a key of the teleprinter keyboard is pressed, a
5-bit character is generated. The teleprinter converts it to
serial format and transmits a sequence of a ''start bit'' (a logical 0 or space), then one after the other the 5 data bits, finishing with a ''stop bit'' (a logical 1 or mark, lasting 1, 1.5 or 2 bits). When a sequence of start bit, 5 data bits and stop bit arrives at the input of the teleprinter, it is converted to a 5-bit word and passed to the printer or VDU. With electromechanical teleprinters, these functions required complicated electromechanical devices, but they are easily implemented with standard digital electronics using
shift register
A shift register is a type of digital circuit using a cascade of flip-flops where the output of one flip-flop is connected to the input of the next. They share a single clock signal, which causes the data stored in the system to shift from one loc ...
s. Special
integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
s have been developed for this function, for example the
Intersil
Intersil is an American semiconductor company headquartered in Milpitas, California. As of February 24, 2017, Intersil is a subsidiary of Renesas. The previous Intersil was formed in August 1999 through the acquisition of the semiconductor busin ...
6402 and 6403. These are stand-alone
UART
A universal asynchronous receiver-transmitter (UART ) is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. It sends data bits one by one, from the least significan ...
devices, similar to computer serial port peripherals.
The 5 data bits allow for only 32 different codes, which cannot accommodate the 26 letters, 10 figures, space, a few
punctuation
Punctuation (or sometimes interpunction) is the use of spacing, conventional signs (called punctuation marks), and certain typographical devices as aids to the understanding and correct reading of written text, whether read silently or aloud. An ...
marks and the required
control codes, such as carriage return, new line, bell, etc. To overcome this limitation, the teleprinter has two ''states'', the ''unshifted'' or ''letters'' state and the ''shifted'' or ''numbers'' or ''figures'' state. The change from one state to the other takes place when the special control codes ''LETTERS'' and ''FIGURES'' are sent from the keyboard or received from the line. In the ''letters'' state the teleprinter prints the letters and space while in the shifted state it prints the numerals and punctuation marks. Teleprinters for languages using other
alphabet
An alphabet is a standardized set of basic written graphemes (called letters) that represent the phonemes of certain spoken languages. Not all writing systems represent language in this way; in a syllabary, each character represents a syll ...
s also use an additional ''third shift'' state, in which they print letters in the alternative alphabet.
The modem is sometimes called the terminal unit and is an electronic device which is connected between the teleprinter and the radio
transceiver
In radio communication, a transceiver is an electronic device which is a combination of a radio ''trans''mitter and a re''ceiver'', hence the name. It can both transmit and receive radio waves using an antenna, for communication purposes. The ...
. The transmitting part of the modem converts the digital signal transmitted by the teleprinter or tape reader to one or the other of a pair of
audio frequency
An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch.
The generally accepted ...
tones, traditionally 2295/2125 Hz (US) or 2125/1955 Hz (Europe). One of the tones corresponds to the ''mark'' condition and the other to the ''space'' condition. These audio tones, then,
modulate an
SSB transmitter to produce the final audio-frequency shift keying (AFSK) radio frequency signal. Some transmitters are capable of direct
frequency-shift keying
Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier signal. The technology is used for communication systems such as telemetry, weather ball ...
(FSK) as they can directly accept the digital signal and change their transmitting frequency according to the ''mark'' or ''space'' input state. In this case the transmitting part of the modem is bypassed.
On reception, the FSK signal is converted to the original tones by mixing the FSK signal with a local oscillator called the BFO or ''
beat frequency oscillator
In a radio receiver, a beat frequency oscillator or BFO is a dedicated oscillator used to create an audio frequency signal from Morse code radiotelegraphy ( CW) transmissions to make them audible. The signal from the BFO is mixed with the recei ...
''. These tones are fed to the demodulator part of the modem, which processes them through a series of filters and detectors to recreate the original digital signal. The FSK signals are audible on a communications radio receiver equipped with a BFO, and have a distinctive "beedle-eeeedle-eedle-eee" sound, usually starting and ending on one of the two tones ("idle on mark").
The transmission speed is a characteristic of the teleprinter while the shift (the difference between the tones representing mark and space) is a characteristic of the modem. These two parameters are therefore independent, provided they have satisfied the
minimum shift size for a given transmission speed. Electronic teleprinters can readily operate in a variety of speeds, but mechanical teleprinters require the change of gears in order to operate at different speeds.
Today, both functions can be performed with modern computers equipped with digital signal processors or
sound card
A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio i ...
s. The sound card performs the functions of the modem and the
CPU performs the processing of the digital bits. This approach is very common in
amateur radio
Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communic ...
, using specialized computer programs like
fldigi
Fldigi (short for Fast light digital) is a free and open-source program which allows an ordinary computer's sound card to be used as a simple two-way data modem. The software is mostly used by amateur radio operators who connect the microphone ...
, MMTTY or MixW.
Before the computer mass storage era, most RTTY stations stored text on paper tape using paper tape punchers and readers. The operator would type the message on the TTY keyboard and punch the code onto the tape. The tape could then be transmitted at a steady, high rate, without typing errors. A tape could be reused, and in some cases - especially for use with ASCII on NC Machines - might be made of plastic or even very thin metal material in order to be reused many times.
The most common test signal is a series of "
RYRYRY" characters, as these form an alternating tone pattern exercising all bits and are easily recognized.
Pangram
A pangram or holoalphabetic sentence is a sentence using every letter of a given alphabet at least once. Pangrams have been used to display typefaces, test equipment, and develop skills in handwriting, calligraphy, and keyboarding.
Origins
The ...
s are also transmitted on RTTY circuits as test messages, the most common one being "
The quick brown fox jumps over the lazy dog
"The quick brown fox jumps over the lazy dog" is an English-language pangram — a sentence that contains all the letters of the alphabet. The phrase is commonly used for touch-typing practice, testing typewriters and computer keyboards, displ ...
", and in French circuits, "Voyez le brick géant que j'examine près du wharf"
Technical specification
The original (or "Baudot") radioteletype system is based almost invariably on the
Baudot code
The Baudot code is an early character encoding for telegraphy invented by Émile Baudot in the 1870s. It was the predecessor to the International Telegraph Alphabet No. 2 (ITA2), the most common teleprinter code in use until the advent of ASCII. ...
or ITA-2 5 bit alphabet. The link is based on character asynchronous transmission with 1 start bit and 1, 1.5 or 2 stop bits. Transmitter modulation is normally
FSK FSK may refer to:
* FSK (band), a German band
* Federal Counterintelligence Service, (Russian ') of Russia
* Fiskerton railway station, in England
* Forskolin, a diterpene
* Forsvarets Spesialkommando, a Norwegian special forces unit
* Fort Scott M ...
(
F1B). Occasionally, an AFSK signal modulating an RF carrier (A2B, F2B) is used on VHF or UHF frequencies. Standard transmission speeds are 45.45, 50, 75, 100, 150 and 300 baud.
Common carrier shifts are 85 Hz (used on LF and VLF frequencies), 170 Hz, 425 Hz, 450 Hz and 850 Hz, although some stations use non-standard shifts. There are variations of the standard Baudot alphabet to cover languages written in Cyrillic, Arabic, Greek etc., using special techniques.
Some combinations of speed and shift are standardized for specific services using the original radioteletype system:
*
Amateur radio
Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communic ...
transmissions are almost always 45.45 baud – 170 Hz, although 75 baud activity is being promoted by BARTG in the form of 4-hour contests.
* Radio amateurs have experimented with ITA-5 (7-bit ASCII) alphabet transmissions at 110 baud – 170 Hz.
*
NATO
The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two No ...
military services use 75 or 100 baud – 850 Hz.
* A few naval stations still use RTTY without encryption for CARB (channel availability broadcasts).
* Commercial, diplomatic and weather services prefer 50 baud – 425 or 450 Hz.
* Russian (and in the past,
Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
) merchant marine communications use 50 baud – 170 Hz.
* RTTY transmissions on
LF and
VLF
Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30 kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave a ...
frequencies use a narrow shift of 85 Hz, due to the limited bandwidth of the antennas.
Early amateur radioteletype history
After World War II,
amateur radio operator
An amateur radio operator is someone who uses equipment at an amateur radio station to engage in two-way personal communications with other amateur operators on radio frequencies assigned to the amateur radio service. Amateur radio operators hav ...
s in the US started to receive obsolete but usable Teletype Model 26 equipment from commercial operators with the understanding that this equipment would not be used for or returned to commercial service. "The Amateur Radioteletype and VHF Society" was founded in 1946 in Woodside, NY. This organization soon changed its name to "The VHF Teletype Society" and started US Amateur Radio operations on 2 meters using audio frequency shift keying (AFSK). The first two-way amateur radioteletype
QSO of record took place in May 1946 between Dave Winters, W2AUF, Brooklyn, NY and W2BFD, John Evans Williams, Woodside Long Island, NY. On the west coast, amateur RTTY also started on 2 meters. Operation on 80 meters, 40 meters and the other High Frequency (HF) amateur radio bands was initially accomplished using make and break keying since frequency shift keying (FSK) was not yet authorized. In early 1949, the first American transcontinental two-way RTTY QSO was accomplished on 11 meters using AFSK between Tom McMullen (W1QVF) operating at
W1AW
W1AW is both the amateur radio call sign and the primary operating station of the American Radio Relay League (ARRL). This station, which is commonly called the Hiram Percy Maxim Memorial Station, is located on the grounds of ARRL Headquarters in ...
and Johnny Agalsoff, W6PSW. The stations effected partial contact on January 30, 1949, and repeated more successfully on January 31. On February 1, 1949, the stations exchanged solid print congratulatory message traffic and rag-chewed. Earlier, on January 23, 1949, William T. Knott, W2QGH, Larchmont, NY, had been able to make rough copy of W6PSW's test transmissions. While QSOs could be accomplished, it was quickly realized that FSK was technically superior to make and break keying. Due to the efforts of Merrill Swan, W6AEE, of "The RTTY Society of Southern California" publisher of ''RTTY'' and Wayne Green, W2NSD, of ''CQ Magazine'', Amateur Radio operators successfully petitioned the U.S.
Federal Communications Commission
The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdiction ...
(FCC) to amend Part 12 of the Regulations, which was effective on February 20, 1953. The amended Regulations permitted FSK in the non-voice parts of the 80, 40 and 20 meter bands and also specified the use of single channel 60 words-per-minute five unit code corresponding to
ITA2
The Baudot code is an early character encoding for telegraphy invented by Émile Baudot in the 1870s. It was the predecessor to the International Telegraph Alphabet No. 2 (ITA2), the most common teleprinter code in use until the advent of ASCII ...
. A shift of 850 hertz plus or minus 50 hertz was specified. Amateur Radio operators also had to identify their station callsign at the beginning and the end of each transmission and at ten-minute intervals using International
Morse code
Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one of ...
. Use of this wide shift proved to be a problem for Amateur Radio operations. Commercial operators had already discovered that narrow shift worked best on the HF bands. After investigation and a petition to the FCC, Part 12 was amended, in March 1956, to allow Amateur Radio Operators to use any shift that was less than 900 hertz.
The FCC Notice of Proposed Rule Making (NPRM) that resulted in the authorization of Frequency Shift Keying (FSK) in the amateur high frequency (HF) bands responded to petitions by the American Radio Relay League (ARRL), the National Amateur Radio Council and Mr. Robert Weinstein. The NPRM specifically states this, and this information may be found in its entirety in the December 1951 Issue of QST. While the New RTTY Handbook gives ARRL no credit, it was published by CQ Magazine and its author was a CQ columnist (CQ generally opposed ARRL at that time).
The first RTTY Contest was held by the RTTY Society of Southern California from October 31 to November 1, 1953. Named the RTTY Sweepstakes Contest, twenty nine participants exchanged messages that contained a serial number, originating station call, check or RST report of two or three numbers, ARRL section of originator, local time (0000-2400 preferred) and date. Example: NR 23 W0BP CK MINN 1325 FEB 15. By the late 1950s, the contest exchange was expanded to include band used. Example: NR 23 W0BP CK MINN 1325 FEB 15 FORTY METERS. The contest was scored as follows: one point for each message sent and received entirely by RTTY and one point for each message received and acknowledged by RTTY. The final score was computed by multiplying the total number of message points by the number of ARRL sections worked. Two stations could exchange messages again on a different band for added points, but the section multiplier did not increase when the same section was reworked on a different band. Each DXCC entity was counted as an additional ARRL section for RTTY multiplier credit.
''RTTY'', later named ''RTTY Journal'', also published the first listing of stations, mostly located in the continental US, that were interested in RTTY in 1956. Amateur Radio operators used this callbook information to contact other operators both inside and outside the United States. For example, the first recorded USA to New Zealand two-way RTTY QSO took place in 1956 between W0BP and ZL1WB.
By the late 1950s, new organizations focused on amateur radioteletype started to appear. The "British Amateur Radio Teletype Group", BARTG, now known as the "British Amateur Radio Teledata Group" was formed in June 1959. The Florida RTTY Society was formed in September 1959. Amateur Radio operators outside of Canada and the United States began to acquire surplus teleprinter and receive permission to get on the air. The first recorded RTTY QSO in the UK occurred in September 1959 between G2UK and G3CQE. A few weeks later, G3CQE had the first G/VE RTTY QSO with VE7KX. This was quickly followed up by G3CQE QSOs with VK3KF and ZL3HJ. Information on how to acquire surplus teleprinter equipment continued to spread and before long it was possible to work all continents on RTTY.
Amateur Radio operators used various equipment designs to get on the air using RTTY in the 1950s and 1960s. Amateurs used their existing receivers for RTTY operation but needed to add a terminal unit, sometimes called a demodulator, to convert the received audio signals to DC signals for the teleprinter.
Most of the terminal unit equipment used for receiving RTTY signals was homebuilt, using designs published in amateur radio publications. These original designs can be divided into two classes of terminal units: audio-type and intermediate frequency converters. The audio-type converters proved to be more popular with amateur radio operators. The Twin City, W2JAV and W2PAT designs were examples of typical terminal units that were used into the middle 1960s. The late 1960s and early 1970s saw the emergence of terminal units designed by W6FFC, such as the TT/L, ST-3, ST-5, and ST-6. These designs were first published in ''RTTY Journal'' starting in September 1967 and ending in 1970.
An adaptation of the W6FFC TT/L terminal unit was developed by Keith Petersen, W8SDZ, and it was first published in the RTTY Journal in September 1967. The drafting of the schematic in the article was done by Ralph Leland, W8DLT.
Amateur Radio operators needed to modify their transmitters to allow for HF RTTY operation. This was accomplished by adding a frequency shift keyer that used a diode to switch a capacitor in and out of the circuit, shifting the transmitter’s frequency in synchronism with the teleprinter signal changing from mark to space to mark. A very stable transmitter was required for RTTY. The typical frequency multiplication type transmitter that was popular in the 1950s and 1960s would be relatively stable on 80 meters but become progressively less stable on 40 meters, 20 meters and 15 meters. By the middle 1960s, transmitter designs were updated, mixing a crystal-controlled high frequency oscillator with a variable low frequency oscillator, resulting in better frequency stability across all Amateur Radio HF bands.
During the early days of Amateur RTTY, the
Worked All Continents
An amateur radio operating award is earned by an amateur radio operator for establishing two-way communication (or "working") with other amateur radio stations. Awards are sponsored by national amateur radio societies, radio enthusiast magazi ...
– RTTY Award was conceived by the RTTY Society of Southern California and issued by RTTY Journal. The first Amateur Radio station to achieve this WAC – RTTY Award was VE7KX. The first stations recognized as having achieved single band WAC RTTY were W1MX (3.5 MHz); DL0TD (7.0 MHz); K3SWZ (14.0 MHz); W0MT (21.0 MHz) and FG7XT (28.0 MHz). The ARRL began issuing WAC RTTY certificates in 1969.
By the early 1970s, Amateur Radio RTTY had spread around the world and it was finally possible to work more than 100 countries via RTTY. FG7XT was the first Amateur Radio station to claim to achieve this honor. However, Jean did not submit his QSL cards for independent review. ON4BX, in 1971, was the first Amateur Radio station to submit his cards to the DX Editor of RTTY Journal and to achieve this honor. The ARRL began issuing
DXCC
An amateur radio operating award is earned by an amateur radio operator for establishing two-way communication (or "working") with other amateur radio stations. Awards are sponsored by national amateur radio societies, radio enthusiast magazine ...
RTTY Awards on November 1, 1976. Prior to that date, an award for working 100 countries on RTTY was only available via RTTY Journal.
In the 1950s through the 1970s, "
RTTY art" was a popular on-air activity. This consisted of (sometimes very elaborate and artistic) pictures sent over rtty through the use of lengthy punched tape transmissions and then printed by the receiving station on paper.
On January 7, 1972, the FCC amended Part 97 to allow faster RTTY speeds. Four standard RTTY speeds were authorized, namely, 60 (45 baud), 67 (50 baud), 75 (56.25 baud) and 100 (75 baud)
words per minute
Words per minute, commonly abbreviated wpm (sometimes uppercased WPM), is a measure of words processed in a minute, often used as a measurement of the speed of typing, reading or Morse code sending and receiving.
Alphanumeric entry
Since word ...
. Many Amateur Radio operators had equipment that was capable of being upgraded to 75 and 100 words per minute by changing teleprinter gears. While there was an initial interest in 100 words per minute operation, many Amateur Radio operators moved back to 60 words per minute. Some of the reasons for the failure of 100 words per minute HF RTTY included poor operation of improperly maintained mechanical teleprinters, narrow bandwidth terminal units, continued use of 170 Hz shift at 100 words per minute and excessive error rates due to multipath distortion and the nature of ionospheric propagation.
The FCC approved the use of
ASCII
ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...
by Amateur Radio stations on March 17, 1980 with speeds up to 300 baud from 3.5 to 21.25 MHz and 1200 baud between 28 and 225 MHz. Speeds up to 19.2 kilobaud was authorized on Amateur frequencies above 420 MHz.
These symbol rates were later modified:
::12m band and below -- 300 bauds symbol rate -- 47 CFR § 97.307 (f)(3)
::10m band -- 1200 bauds symbol rate -- 47 CFR § 97.307 (f)(4)
::6m and 2m bands -- 19.6 kilobauds symbol rate -- 47 CFR § 97.307 (f)(5)
::1.25m and 70cm bands -- 56 kilobauds symbol rate -- 47 CFR § 97.307 (f)(6)
::33 cm band and above -- symbol rate not specified -- 47 CFR § 97.307 (f)(7)
The requirement for Amateur Radio operators in the United States to identify their station callsign at the beginning and the end of each digital transmission and at ten-minute intervals using International Morse code was finally lifted by the FCC on June 15, 1983.
Comparison with other modes
RTTY has a typical
baud rate
In telecommunication and electronics, baud (; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel.
It is the unit for symbol rate or modul ...
for Amateur operation of 45.45 baud (approximately 60 words per minute). It remains popular as a "keyboard to keyboard" mode in Amateur Radio.
[American Radio Relay League, The ARRL Handbook for Radio Communications, 87th ed., 2010, Chapter 16] RTTY has declined in commercial popularity as faster, more reliable alternative data modes have become available, using satellite or other connections.
For its transmission speed, RTTY has low
spectral efficiency
Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system. It is a measure of how efficiently a limited frequency spectrum is ut ...
. The typical RTTY signal with 170 Hz shift at 45.45 baud requires around 250 Hz receiver bandwidth, more than double that required by
PSK31
PSK31 or " Phase Shift Keying, 31 Baud", also BPSK31 and QPSK31, is a popular computer-sound card-generated radioteletype mode, used primarily by amateur radio operators to conduct real-time keyboard-to-keyboard chat, most often using frequenci ...
. In theory, at this baud rate, the shift size can be decreased to 22.725 Hz, reducing the overall band footprint substantially. Because RTTY, using either
AFSK
Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier signal. The technology is used for communication systems such as telemetry, weather ball ...
or
FSK FSK may refer to:
* FSK (band), a German band
* Federal Counterintelligence Service, (Russian ') of Russia
* Fiskerton railway station, in England
* Forskolin, a diterpene
* Forsvarets Spesialkommando, a Norwegian special forces unit
* Fort Scott M ...
modulation, produces a waveform with constant power, a transmitter does not need to use a
linear amplifier
A linear amplifier is an electronic circuit whose output is proportional to its input, but capable of delivering more power into a load. The term usually refers to a type of radio-frequency (RF) power amplifier, some of which have output power m ...
, which is required for many digital transmission modes. A more efficient
Class C amplifier
In electronics, power amplifier classes are letter symbols applied to different power amplifier types. The class gives a broad indication of an amplifier's characteristics and performance. The classes are related to the time period that the active ...
may be used.
RTTY, using either AFSK or FSK modulation, is moderately resistant to vagaries of HF propagation and interference, however modern digital modes, such as
MFSK
Multiple frequency-shift keying (MFSK) is a variation of frequency-shift keying (FSK) that uses more than two frequencies. MFSK is a form of M-ary orthogonal modulation, where each symbol consists of one element from an alphabet of orthogonal wave ...
, use
Forward Error Correction
In computing, telecommunication, information theory, and coding theory, an error correction code, sometimes error correcting code, (ECC) is used for controlling errors in data over unreliable or noisy communication channels. The central idea is ...
to provide much better data reliability.
Primary users
Principally, the primary users are those who need robust shortwave communications. Examples are:
* All military departments, all over the world (using cryptography)
* Diplomatic services all over the world (using cryptography)
* Weather reports are transmitted by the US Coast Guard nearly continuously
* RTTY systems are also fielded by
amateur radio operator
An amateur radio operator is someone who uses equipment at an amateur radio station to engage in two-way personal communications with other amateur operators on radio frequencies assigned to the amateur radio service. Amateur radio operators hav ...
s, and are popular for long-distance contacts
One regular service transmitting RTTY meteorological information is the
German Meteorological Service
The () or DWD for short, is the German Meteorological Service, based in Offenbach am Main, Germany, which monitors weather and meteorological conditions over Germany and provides weather services for the general public and for nautical, avia ...
(Deutscher Wetterdienst or DWD). The DWD regularly transmit two programs on various frequencies on
LF and
HF in standard RTTY (ITA-2 alphabet). The list of callsigns, frequencies,
baud
In telecommunication and electronics, baud (; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel.
It is the unit for symbol rate or modulatio ...
rates and shifts are as follows:
The DWD signals can be easily received in Europe, North Africa and parts of North America.
Pronunciation
RTTY (in English) may be spoken as "radioteletype", by its letters: R-T-T-Y, or simply as /ˈɹɪti/ or /ˈɹəti/
Media
See also
Related technical references
*
Asynchronous serial communication
Asynchronous serial communication is a form of serial communication in which the communicating endpoints' interfaces are not continuously synchronized by a common clock signal. Instead of a common synchronization signal, the data stream contai ...
*
Modem
A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ...
*
Teleprinter
A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...
*
Telex
The telex network is a station-to-station switched network of teleprinters similar to a Public switched telephone network, telephone network, using telegraph-grade connecting circuits for two-way text-based messages. Telex was a major method of ...
*
Types of radio emissions
The International Telecommunication Union uses an internationally agreed system for classifying radio frequency signals. Each type of radio emission is classified according to its bandwidth, method of modulation, nature of the modulating signal, ...
*
UART
A universal asynchronous receiver-transmitter (UART ) is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. It sends data bits one by one, from the least significan ...
Digital HF radio communications systems
*
ACARS
In aviation, ACARS (; an acronym for Aircraft Communications Addressing and Reporting System) is a digital datalink system for transmission of short messages between aircraft and ground stations via airband radio or satellite. The protocol was des ...
, used by commercial aviation – packet based
*
CLOVER2000 CLOVER is the name of a series or class of modem modulation techniques (“waveforms”) specifically designed for use over high frequency (HF) radio systems.
* CLOVER-II was the first CLOVER waveform sold commercially, developed by Ray Petit, W7G ...
developed by HAL company, USA, for Radio Amateur application
*
Hellschreiber
The Hellschreiber, Feldhellschreiber or Typenbildfeldfernschreiber (also Hell-Schreiber named after its inventor Rudolf Hell) is a facsimile-based teleprinter invented by Rudolf Hell. Compared to contemporary teleprinters that were based on ty ...
, a FAX-RTTY hybrid, very old system from the 1930s
*
MFSK
Multiple frequency-shift keying (MFSK) is a variation of frequency-shift keying (FSK) that uses more than two frequencies. MFSK is a form of M-ary orthogonal modulation, where each symbol consists of one element from an alphabet of orthogonal wave ...
including COQUELET, PICCOLO and
Olivia MFSK
Olivia MFSK is an amateur radioteletype protocol, using multiple frequency-shift keying (MFSK) and designed to work in difficult (low signal-to-noise ratio plus multipath propagation) conditions on shortwave bands. The signal can be accurately re ...
, also referred to generically as Polytone
*
MT63
MT63 is a digital radio modulation mode for transmission in high-noise situations developed by Pawel Jalocha SP9VRC. MT63 is designed for keyboard-to-keyboard conversation modes, on HF amateur radio bands.
Description
MT63 distributes the en ...
, developed and used by Radio Amateurs and some government agencies
*
Navtex
NAVTEX (NAVigational TEleX), sometimes styled Navtex or NavTex, is an international automated medium frequency direct-printing service for delivery of navigational and meteorological warnings and forecasts, as well as urgent maritime safety inf ...
, used for maritime weather reports, with FEC error control code using the
SITOR SITOR ( SImplex Teletype Over Radio) is a system for transmitting text messages. It was developed in the 1960s by Koninklijke TNT Post as an improvement over radioteletype (RTTY). Although it uses the same frequency-shift keying (FSK) modulation us ...
-B system
*
PSK31
PSK31 or " Phase Shift Keying, 31 Baud", also BPSK31 and QPSK31, is a popular computer-sound card-generated radioteletype mode, used primarily by amateur radio operators to conduct real-time keyboard-to-keyboard chat, most often using frequenci ...
and
PSK63
PSK63 (meaning Phase Shift Keying at a rate of 63 baud) is a Digital data, digital :Radio modulation modes, radio modulation mode used primarily in the amateur radio field to conduct real-time keyboard-to-keyboard informal text Synchronous conferen ...
developed and used by Radio Amateurs
*
PACTOR
PACTOR is a :Radio modulation modes, radio modulation mode used by amateur radio operators, Marine and mobile radio telephony, marine radio stations, military or government users such as the US Department of Homeland Security, and radio stations in ...
, a packet SITOR variant, developed by Radio Amateurs in Germany
*
AX.25
AX.25 (Amateur X.25) is a data link layer protocol originally derived from layer 2 of the X.25 protocol suite and designed for use by amateur radio operators. It is used extensively on amateur packet radio networks.
AX.25 v2.0 and later occupies t ...
, the original digital PacketRadio standard developed by Amateurs
*
Automatic Packet Reporting System
Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time digital communications of information of immediate value in the local area. Data can include object Global Positioning System (GPS) coordinates, weather st ...
, built on top of AX.25, used by Amateurs and Emergency services and which includes GPS Positioning
*
Q15X25 Q15X25 is a communications protocol for sending data over a radio link. It was designed by amateur radio operator Pawel Jalocha, SP9VRC, to be an open communications standard. Like all amateur radio communications modes, this protocol uses open tran ...
, a Radio Amateur created packet format (AX25), similar to the commercial X25 standard
*
Fast Simple QSO or FSQ, an HF mode developed by Radio Amateurs for us in NVIS and sunrise/sunset conditions.
*
SITOR SITOR ( SImplex Teletype Over Radio) is a system for transmitting text messages. It was developed in the 1960s by Koninklijke TNT Post as an improvement over radioteletype (RTTY). Although it uses the same frequency-shift keying (FSK) modulation us ...
, (SImplex Teleprinting Over Radio) a commercial RTTY variant with error control (the Radio Amateur version is called
AMTOR
The Amtor or Venus series is a science fantasy series consisting of four novels and one novelette written by American author Edgar Rice Burroughs. Most of the stories were first serialized in '' Argosy'', an American pulp magazine. It is someti ...
)
*
Sailmail SailMail is radio based e-mail system designed for boat owners operating beyond line-of-sight radio links to the internet. Much of its underlying technology is built upon the Winlink software originally developed by amateur radio enthusiasts.
Oper ...
, a commercial HF mail system
*
WSJT, a computer program used for weak-signal radio communication between amateur radio operators
References
Further reading
*
*
*
*
Getting Started on RTTY Getting started on RTTY using MMTTY
*
RTTY.COM a repository of Amateur RTTY information
British Amateur Radio Teledata Group (BARTG)by Kok Chen, W7AY. A technology review for the early period until ca 1965.
{{Authority control
Quantized radio modulation modes
Military radio systems
Amateur radio
Wireless communication systems