PACTOR is a radio modulation mode used by

amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency radio spectrum, spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emer ...

operators, marine radio stations, military or government users such as the

United States Department of Homeland Security The United States Department of Homeland Security (DHS) is the U.S. United States federal executive departments, federal executive department responsible for public security, roughly comparable to the Interior minister, interior, Home Secretary ...

, and radio stations in isolated areas to send and receive digital information via radio. PACTOR is an evolution of both AMTOR and

packet radio In digital radio, packet radio is the application of packet switching techniques to digital radio communications. Packet radio uses a packet switching Communication protocol, protocol as opposed to circuit switching or message switching protocols ...

; its name is a

portmanteau In linguistics, a blend—also known as a blend word, lexical blend, or portmanteau—is a word formed by combining the meanings, and parts of the sounds, of two or more words together.

of these two technologies' names. PACTOR uses a combination of simple FSK modulation, and the ARQ protocol for robust error detection and data throughput. Generational improvements to PACTOR include PACTOR II, PACTOR III, and PACTOR IV which are capable of higher speed transmission. PACTOR is most commonly used on frequencies between 1

MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base u ...

and 30

History

PACTOR ''(Latin: The mediator)'' was developed by Special Communications Systems GmbH (SCS) and released to the public in 1991. PACTOR was developed in order to improve the reception of digital data when the received signal was weak or noisy. It combines the

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

efficiency of

with the

error-correction In information theory and coding theory with applications in computer science and telecommunications, error detection and correction (EDAC) or error control are techniques that enable reliable delivery of digital data over unreliable communi ...

(CRC) and automatic repeat request (ARQ) of AMTOR. Amateur radio operators were instrumental in developing and implementing these digital modes.

Current uses

PACTOR radio equipment consists of an HF transceiver, a computer and a

terminal node controller A terminal node controller (TNC) is a device used by amateur radio operators to participate in AX.25 packet radio Computer network, networks. It is similar in function to the Packet Assembler/Disassemblers used on X.25 networks, with the additi ...

. Software running on the computer drives the terminal node controller. The most commonly used amateur program for this purpose is ''Airmail''. PACTOR is used by Amateur

Bulletin board system A bulletin board system (BBS), also called a computer bulletin board service (CBBS), is a computer server running list of BBS software, software that allows users to connect to the system using a terminal program. Once logged in, the user perfor ...

operators to exchange public messages, and open conversations across the world. It is also used by the NTSD (digital) portion of the

ARRL The American Radio Relay League (ARRL) is the largest membership association of amateur radio enthusiasts in the United States. ARRL is a non-profit organization and was co-founded on April 6, 1914, by Hiram Percy Maxim and Clarence D. Tuska of H ...

's National Traffic System (NTS) to pass digital ARRL Radiograms. Newer PACTOR modes are used to transfer large binary data files and Internet e-mail, particularly via the

Winlink Winlink, or formally, Winlink Global Radio Email (registered US Service Mark), also known as the Winlink 2000 Network, is a worldwide radio messaging system that uses amateur-band radio frequencies and government frequencies to provide radio int ...

global e-mail system. The SailMail network transfers e-mail on behalf of marine stations.

Technical characteristics

PACTOR is a set of standardized modes used by radio operators for FSK

radioteletype 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 ...

transfer of digital information over

shortwave Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (app ...

bands. Effective radio-frequency communications over long distances over hostile radio paths require that special attention be paid to the rate at which data is repeated and error correction. To reduce the amount of data sent, on-line data compression is utilized, along with memory ARQ error correction. PACTOR utilizes very rapid

time-division duplex A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow ...

ing, giving PACTOR communications its characteristic cricket-like chirping sound when listened through a single-sideband (SSB) receiver. Depending on the version of PACTOR protocol used and the radio-frequency conditions, PACTOR transmission speeds range from 20 to 5200 bits per second (bit/s; net rate) or 9000 bit/s gross rate utilizing speed 10 (32-QAM). The International Telecommunication Union (ITU) emission designators: * Pactor I is 340HJ2D or 440HJ2D (at a symbol rate up to 200 symbols per second). * Pactor II is 450HJ2D (at a symbol rate of 100 symbols per second). * Pactor III is 2K20J2D (at a symbol rate of 100 symbols per second). * Pactor IV is 2K20J2D or 2K40J2D (at a symbol rate up to 1800 symbols per second).

Availability and monitoring

A robust network of PACTOR stations has been established to transfer data between radio stations and the Internet, extending Internet access to sea-based and other isolated users, led by volunteers involved with

, under the auspicies of ARSFI (a Florida-based non-profit organization). Pactor modes other than level 1 (P1) are not open source, but are publicly documented and can be monitored and decoded easily over the air by third parties using free Raspberry Pi software ("PMON for Raspberry Pi") or PMON utility on the modem itself.

References

External links