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{{Short description|Digital radio modulation mode}}
{{More citations needed|date=April 2019}}
'''PACTOR''' is a [[:Category: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 [[United States Department of Homeland Security]], and radio stations in isolated areas to send and receive digital information via radio.{{citation needed|date=May 2021}}

PACTOR is an evolution of both [[AMTOR]] and [[packet radio]];<ref name="QEX1991">{{cite journal |last1=Helfert |first1=Hans-Peter |title=PACTOR—Radioteletype with Memory ARQ and Data Compression |journal=QEX Magazine |date=October 1991 |pages=3–6 |url=https://archive.org/details/QEX19812016/QEX%201991/QEX%201991-10/page/n3/mode/2up}}</ref> its name is a [[portmanteau]] of these two technologies' names.
PACTOR uses a combination of simple [[Frequency-shift keying|FSK]] modulation{{citation needed|date=May 2021}}, and the [[Automatic repeat request|ARQ]] protocol for robust error detection and data throughput.{{citation needed|date=May 2021}} Generational improvements to PACTOR include PACTOR&nbsp;II, PACTOR&nbsp;III, and PACTOR&nbsp;IV which are capable of higher speed transmission. PACTOR is most commonly used on frequencies between 1&nbsp;[[MHz]] and 30&nbsp;[[MHz]].{{citation needed|date=May 2021}}

== History ==
{{More citations needed section|date=May 2021}}
PACTOR ''(Latin: The mediator)'' was developed by Special Communications Systems GmbH (SCS) and released to the public in 1991.<ref name="QEX1991" />

PACTOR was developed in order to improve the reception of digital data when the received signal was weak or noisy.<ref name="QEX1991" /> It combines the [[Bandwidth (signal processing)|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.{{citation needed|date=May 2021}}

==Current uses==
{{More citations needed section|date=April 2019}}
PACTOR radio equipment consists of an HF transceiver, a computer and a [[terminal node controller]].{{citation needed|date=May 2021}} Software running on the computer drives the terminal node controller.{{citation needed|date=May 2021}} The most commonly used amateur program for this purpose is ''Airmail''.{{citation needed|date=May 2021}}

PACTOR is used by Amateur [[Bulletin board system]] operators to exchange public messages, and open conversations across the world.{{citation needed|date=May 2021}} It is also used by the NTSD (digital) portion of the [[ARRL]]'s [[National Traffic System| National Traffic System (NTS)]] to pass digital [[ARRL Radiogram]]s.{{citation needed|date=May 2021}} Newer PACTOR modes are used to transfer large binary data files and Internet e-mail, particularly via the [[Winlink]] global e-mail system.{{citation needed|date=May 2021}}

The [[Sailmail|SailMail]] network transfers e-mail on behalf of marine stations.<ref>{{cite web |website=Sail Mail |url=http://www.sailmail.com/ |title=Sail-mail e-mail service for yachts via Iridium, Inmarsat, or SSB |access-date=1 September 2010}}</ref>

== Technical characteristics ==
{{More citations needed section|date=April 2019|talk=Better references needed}}
PACTOR is a set of standardized modes used by radio operators for FSK [[radioteletype]] transfer of digital information over [[shortwave radio|shortwave]] bands.<ref name="WavecomPactor">{{cite web |title=PACTOR Packet Teleprinting Over Radio |url=http://www.wavecom.ch/content/pdf/advanced_protocol_pactor.pdf |website=Wavecom |publisher=WAVECOM ELEKTRONIK AG |access-date=29 May 2021}}</ref>

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.<ref name="SCSP2Proto">{{cite book |title=The PACTOR-2 Protocol |publisher=SCS Spezielle Communications Systeme GmbH |url=https://www.p4dragon.com/download/PACTOR-2%20Protocol.pdf |ref=SCSP2Proto}}</ref>

To reduce the amount of data sent, on-line data compression is utilized, along with memory ARQ error correction.<ref name="SCSADC">{{cite book |title=PACTOR-2/3/4 Advanced Data Compression |publisher=SCS Spezielle Communications Systeme GmbH |url=https://www.p4dragon.com/download/PACTOR_Advanced_Data_Compression.pdf}}</ref>

PACTOR utilizes very rapid [[time-division duplex]]ing, giving PACTOR communications its characteristic cricket-like chirping sound when listened through a [[Single-sideband modulation|single-sideband (SSB)]] receiver.{{clarify|reason=PACTOR has many different submodes and sounds|date=April 2019}}

Depending on the version of PACTOR protocol used and the radio-frequency conditions, PACTOR transmission speeds range from 20 to 5200&nbsp;bits per second (bit/s; net rate) or 9000&nbsp;bit/s gross rate utilizing speed&nbsp;10 (32-QAM).<ref>{{cite news |department=News |website=PACTOR |url=http://www.pactor.com/compare.shtml |title=More on comparisons of digital HF modes |access-date=1 September 2010}}</ref><ref name="PACTOR IV">{{cite web |series=PACTOR&nbsp;IV |url=http://www.p4dragon.com/en/PACTOR-4.html |website=p4dragon.com |title=Technical details on the Pactor-IV protocol |access-date=25 November 2022 |url-status=dead |archive-url=https://web.archive.org/web/20151023162156/http://www.p4dragon.com/en/PACTOR-4.html |archive-date=23 October 2015}}</ref>

The [[International Telecommunication Union|International Telecommunication Union (ITU)]] emission [[Types of radio emissions|designators]]:
* Pactor I is 340HJ2D or 440HJ2D (at a symbol rate up to 200&nbsp;symbols per second).<ref name="SCSWaveformSummary">{{cite web |title=Summary on SCS Waveforms |url=https://www.scs-ptc.com/download/SCS_Waveforms_Emission_Designators.pdf |website=SCS |publisher=Spezielle Communications Systeme GmbH & Co. KG |access-date=1 June 2021}}</ref>
* Pactor II is 450HJ2D (at a symbol rate of 100&nbsp;symbols per second).<ref name="SCSWaveformSummary" /><ref name="SCSP2Proto"/><ref name="ITU-R M.1732-2">{{cite web |id=ITU-R M.1732-2 |url=https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1732-2-201701-I!!PDF-E.pdf |title=Characteristics of systems operating in the amateur and amateur-satellite services for use in sharing studies |year=2017 |publisher=International Telecommunication Union}}</ref>
* Pactor III is 2K20J2D (at a symbol rate of 100&nbsp;symbols per second).<ref name="SCSWaveformSummary" /><ref name="SCSP3Proto">{{cite book |title=The PACTOR-3 Protocol |publisher=Spezielle Communications Systeme GmbH |url=https://www.p4dragon.com/download/PACTOR-3%20Protocol.pdf}}</ref><ref name="ITU-R M.1798-2">{{cite web |id=ITU-R M.1798-2 |url=https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1798-2-202102-I!!PDF-E.pdf |title=Characteristics of HF radio equipment for the exchange of digital data and electronic mail in the maritime mobile service |year=2021 |publisher=International Telecommunication Union}}</ref>
* Pactor IV is 2K20J2D or 2K40J2D (at a symbol rate up to 1800&nbsp;symbols per second).<ref name="SCSWaveformSummary" /><ref name="SCSP4Proto">{{cite book |title=The PACTOR-4 Protocol |publisher=Spezielle Communications Systeme GmbH |url=https://www.p4dragon.com/download/PACTOR-4%20Protocol.pdf}}</ref><ref name="PACTOR IV"/>

== 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 [[Winlink]], under the auspicies of ARSFI (a Florida-based non-profit organization).<ref name="winlink">{{cite web |title=A brief guide to the elements of Winlink&nbsp;2000 |url=http://www.winlink.org/node/12 |work=Winlink 2000 |access-date=25 November 2022 |url-status=dead |archive-url=https://web.archive.org/web/20080512053510/http://www.winlink.org/node/12 |archive-date=12 May 2008}}</ref>

Pactor modes other than level&nbsp;1 (P1) are not open source,<ref>{{cite web |title=Original request to FCC for Pactor&nbsp;I in Amateur Radio by ARRL |year=1995 |url=https://www.fcc.gov/document/amendment-part-97-digital-codes}}</ref><ref>{{cite web |title=Pactor&nbsp;I open source published in QEX, TAPR, 1994 |url=https://www.tapr.org/kits_an93.html |access-date=25 November 2022 |url-status=dead |archive-url=https://web.archive.org/web/20151109104848/https://www.tapr.org/kits_an93.html |archive-date=9 November 2015}}</ref> but are publicly documented<ref>{{cite web |url=https://www.scs-ptc.com/de/Downloads.html |title=Downloads |website=www.scs-ptc.com |access-date=2022-11-25 |df=dmy-all |url-status=dead |archive-url=https://web.archive.org/web/20180325055429/https://www.scs-ptc.com/de/Downloads.html |archive-date=2018-03-25}}</ref> and can be monitored and decoded easily over the air by third parties using free Raspberry Pi software ("PMON for Raspberry Pi")<ref>{{cite web |url=https://www.scs-ptc.com/pmon.html |title=PMON |website=www.scs-ptc.com |access-date=2024-11-28 |df=dmy-all}}</ref> or PMON utility on the modem itself.<ref>{{cite web |url=https://www.p4dragon.com/download/Update_Info_DR7X00_Version_1_17_English.pdf |title=Update Info DR7X00 vers.&nbsp;1.17 |language=en |website=p4dragon.com |access-date=25 November 2022 |url-status=dead |archive-url=https://web.archive.org/web/20200614235942/https://www.p4dragon.com/en/PMON.html |archive-date=14 June 2020}}</ref>

==See also==
* [[Shortwave]]
* [[Radioteletype]]
* [[Winmor]]

==References==
{{Reflist|25em}}

{{refbegin}}
* {{cite book |title=ARRL's HF digital handbook |author=Steve Ford, WB8IMY |publisher=The [[American Radio Relay League]] |year=2001 |location=Newington, CT |chapter=Chapter 5 - PACTOR |isbn=0-87259-823-3}}
{{Refend}}

==External links==
* {{cite web |url=http://www.scs-ptc.com/pactor/pactor |archive-url=https://web.archive.org/web/20090816151648/http://www.scs-ptc.com/pactor/pactor |archive-date=2009-08-16 |df=dmy-all |title=pactor |website=scs-ptc.com}}
* {{cite web |url=http://www.p4dragon.com/en/PACTOR-4.html |title=PACTOR-4 |website=p4dragon.com |url-status=dead |archive-url=https://web.archive.org/web/20151023162156/http://www.p4dragon.com/en/PACTOR-4.html |archive-date=23 October 2015}}
* {{cite web |url=http://www.winlink.org/ |title=winlink.org}}
* {{cite web |url=http://www.airmail2000.com/ |title=airmail2000.com}}
* {{cite web |url=https://www.qsl.net/kd6pag/usenet/PACTOR.txt |title=Pactor-1 Specification}}

{{Digital modes}}

{{Amateur radio topics}}
{{Two-way radio}}
{{Telecommunications}}

[[Category:Digital amateur radio]]
[[Category:History of radio]]
[[Category:Radio technology]]
[[Category:Quantized radio modulation modes]]
[[Category:Packet radio]]