AMTOR
Encyclopedia
AMTOR is a type of telecommunications system that consists of two or more electromechanical teleprinters in different locations that send and receive messages to one another. AMTOR is a specialized form of RTTY
protocol
. The term is an acronym for Amateur Teleprinting Over Radio and is derived from ITU-R recommendation 476-1 and is known commercially as SITOR (Simplex Telex Over radio) developed primarily for maritime use in the 1970s. AMTOR was developed in 1978 by Peter Martinez, G3PLX with the first contact taking place in September 1978 with G3YYD on the 2m Amateur band. It was developed on home made Motorola 6800 based microcomputers in assembler code. It was used extensively by amateur radio
operators in the 80s and 90s but has now fallen out of use as improved PC based data modes are now used.
AMTOR improves on RTTY by incorporating error detection or error correction techniques. The protocol remains relatively uncomplicated and AMTOR performs well even in poor and noisy HF conditions. AMTOR operates in one of two modes: an error detection mode and an automatic repeat request (ARQ
) mode.
The AMTOR protocol utilizes a 7-bit
code for each character, with each code-word having four mark and three space bits. If the received code does not match a four-to-three (4:3) ratio, the receiver assumes an error has occurred. In error detection mode, the code word will be dropped; in error correction mode, the receiver requests that the original data be resent. AMTOR also supports FEC
in which simple bit-errors can be corrected.
AMTOR utilizes FSK, with a frequency shift of 170 Hz, and a symbol rate of 100 Baud
.
AMTOR is rarely used today, as other protocols such as PSK31
are becoming favoured by amateur operators for real-time text communications. The ARRL has announced that as of August 17, 2009, it will be dropping AMTOR bulletin service in favor of the more popular MFSK16 and PSK31 modes.
Radioteletype
Radioteletype is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations, later superseded by personal computers running software to emulate teleprinters, connected by radio rather than a wired link.The term radioteletype is used to...
protocol
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
. The term is an acronym for Amateur Teleprinting Over Radio and is derived from ITU-R recommendation 476-1 and is known commercially as SITOR (Simplex Telex Over radio) developed primarily for maritime use in the 1970s. AMTOR was developed in 1978 by Peter Martinez, G3PLX with the first contact taking place in September 1978 with G3YYD on the 2m Amateur band. It was developed on home made Motorola 6800 based microcomputers in assembler code. It was used extensively by amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
operators in the 80s and 90s but has now fallen out of use as improved PC based data modes are now used.
AMTOR improves on RTTY by incorporating error detection or error correction techniques. The protocol remains relatively uncomplicated and AMTOR performs well even in poor and noisy HF conditions. AMTOR operates in one of two modes: an error detection mode and an automatic repeat request (ARQ
ARQ
Automatic Repeat reQuest , also known as Automatic Repeat Query, is an error-control method for data transmission that uses acknowledgements and timeouts to achieve reliable data...
) mode.
The AMTOR protocol utilizes a 7-bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
code for each character, with each code-word having four mark and three space bits. If the received code does not match a four-to-three (4:3) ratio, the receiver assumes an error has occurred. In error detection mode, the code word will be dropped; in error correction mode, the receiver requests that the original data be resent. AMTOR also supports FEC
Forward error correction
In telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....
in which simple bit-errors can be corrected.
AMTOR utilizes FSK, with a frequency shift of 170 Hz, and a symbol rate of 100 Baud
Baud
In telecommunications and electronics, baud is synonymous to symbols per second or pulses per second. It is the unit of symbol rate, also known as baud rate or modulation rate; the number of distinct symbol changes made to the transmission medium per second in a digitally modulated signal or a...
.
AMTOR is rarely used today, as other protocols such as PSK31
PSK31
PSK31 or "Phase Shift Keying, 31 Baud" is a digital radio modulation mode, used primarily in the amateur radio field to conduct real-time keyboard-to-keyboard informal text chat between amateur radio operators.- History :...
are becoming favoured by amateur operators for real-time text communications. The ARRL has announced that as of August 17, 2009, it will be dropping AMTOR bulletin service in favor of the more popular MFSK16 and PSK31 modes.