- PACTOR
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PACTOR is a radio modulation mode used by amateur radio operators, marine radio stations, and radio stations in isolated areas to send and receive digital information via radio. A robust network of PACTOR stations has been established to relay data between radio stations and the Internet, extending Internet access to sea based and other isolated users [1]. PACTOR utilizes an almost ideal combination of simple FSK modulation, and the ARQ protocol for robust error detection and data throughput. Generational improvements to PACTOR include PACTOR II and PACTOR III, which are capable of higher speed transmission.
Contents
History
PACTOR (Latin: The mediator) was developed by Special Communications Systems GmbH (SCS) and released to the public in 1991. It was developed in order to improve the reception of digital data when the received signal was weak or noisy. PACTOR is an evolution of both AMTOR and packet radio; its name is a portmanteau of these two technologies. PACTOR combines the bandwidth efficiency of packet radio with the error-correction (CRC) and automatic repeat request (ARQ) of AMTOR. Amateur radio operators were instrumental in developing and implementing these digital modes. PACTOR is most commonly used on frequencies between 1 MHz and 30 MHz.
Current uses
PACTOR is an established standard for FSK radioteletype on shortwave amateur and marine radio. Newer versions are used by amateur radio operators to transfer large binary data files and to accomplish Internet E-mail access over shortwave radio. Winlink is a global communications system which uses PACTOR. PACTOR is also used by the sailmail network for e-mail transfer over U.S. Federal Communications Commission assigned Marine radio frequencies.[2]
Amateur radio operators and Marine operators use similar equipment to send and receive data using the PACTOR digital mode. The equipment consists of an HF transceiver, a computer and a terminal node controller. Software running on the computer controls the terminal node controller. The most commonly used program for this purpose is Airmail.
PACTOR is also used by the ARRL's National Traffic System (NTS) for digital transmission of NTS Traffic, referred to as NTSD. Pactor is also used by Amateur Bulletin Board operators to exchange public messages and open conversations across the world.
Technical characteristics
HF data transmission by radio amateurs uses medium power (100 watts) over long distances (100 to 4000 km). Effective radio-frequency communications over such 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. By combining these open technologies, PACTOR achieves a power efficiency much greater than that of older protocols such as packet, AMTOR, or RTTY. PACTOR has a very narrow waveform and occupies the same band space as analog 300 baud packet.
PACTOR utilizes very rapid Time-Division Duplexing, giving PACTOR communications its characteristic cricket-like chirping sound when listened through a single-sideband receiver.
Depending on the version of PACTOR protocol used and the radio-frequency conditions, PACTOR transmission speeds range from 20 to 200 characters per second [3].
Criticism
Cost is an important consideration when choosing PACTOR equipment. PACTOR I is open technology and modems can be purchased in the $50–$150 price range and are in ample supply. The two enhanced modes, PACTOR II and PACTOR III, are much faster but have been kept proprietary by the German company, SCS, that developed them. As a result, SCS is the only source for modems capable of these modes. The price of these modems—in some cases as much as a HF radio—discourage many potential users [4].
Like all digital radio modulation modes, PACTOR transmissions have the potential to disrupt other modes of communication on the same or nearby frequencies. Radio operators using PACTOR are encouraged to follow "good operating practices" to ensure that they do not interfere with other stations. In certain configurations, Pactor II and III utilize a proprietary data compression technology. As the data is compressed, and the decompression algorithm is not publicly known, the contents of PACTOR transmissions are unreadable to anyone without a PACTOR capable terminal node controller.
See also
References
- ^ "A Brief Guide to the Elements of Winlink 2000". Winlink 2000. http://www.winlink.org/node/12. Retrieved 1 September 2010.
- ^ "SailMail". SailMail Email Service for Yachts via Iridium, Inmarsat, or SSB. http://www.sailmail.com/. Retrieved 1 September 2010.
- ^ "PACTOR News". More on comparisons of digital HF modes. http://www.pactor.com/compare.shtml. Retrieved 1 September 2010.
- ^ "Linux.com". Concerned hams question amateur radio choice of closed code and controller. http://www.linux.com/archive/feature/36570. Retrieved 1 September 2010.
External links
Amateur radio digital modes Frequency-shift keying (FSK) RTTY · AMTOR · PACTOR · CLOVER2000 · Packet radio (Bell 103 · Bell 202)
Multiple frequency-shift keying (MFSK) Olivia MFSK · JT65 · FSK441 · JT6M · WSPR
Phase-shift keying (PSK) Non-traditional digital modes Categories:- Quantized radio modulation modes
- Packet radio
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