PACTOR (Latin: The mediator) was developed by Special Communications Systems GmbH (SCS) and released to the public in 1991.2
PACTOR was developed in order to improve the reception of digital data when the received signal was weak or noisy.3 It 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 radio equipment consists of an HF transceiver, a computer and a terminal node controller. 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 operators to exchange public messages, and open conversations across the world. It is also used by the NTSD (digital) portion of the ARRL'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 global e-mail system.
The SailMail network transfers e-mail on behalf of marine stations.4
PACTOR is a set of standardized modes used by radio operators for FSK radioteletype transfer of digital information over shortwave bands.5
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.6
To reduce the amount of data sent, on-line data compression is utilized, along with memory ARQ error correction.7
PACTOR utilizes very rapid time-division duplexing, 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).89
The International Telecommunication Union (ITU) emission designators:
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).20
Pactor modes other than level 1 (P1) are not open source,2122 but are publicly documented23 and can be monitored and decoded easily over the air by third parties using free Raspberry Pi software ("PMON for Raspberry Pi")24 or PMON utility on the modem itself.25
Helfert, Hans-Peter (October 1991). "PACTOR—Radioteletype with Memory ARQ and Data Compression". QEX Magazine: 3–6. https://archive.org/details/QEX19812016/QEX%201991/QEX%201991-10/page/n3/mode/2up ↩
"Sail-mail e-mail service for yachts via Iridium, Inmarsat, or SSB". Sail Mail. Retrieved 1 September 2010. http://www.sailmail.com/ ↩
"PACTOR Packet Teleprinting Over Radio" (PDF). Wavecom. WAVECOM ELEKTRONIK AG. Retrieved 29 May 2021. http://www.wavecom.ch/content/pdf/advanced_protocol_pactor.pdf ↩
The PACTOR-2 Protocol (PDF). SCS Spezielle Communications Systeme GmbH. https://www.p4dragon.com/download/PACTOR-2%20Protocol.pdf ↩
PACTOR-2/3/4 Advanced Data Compression (PDF). SCS Spezielle Communications Systeme GmbH. https://www.p4dragon.com/download/PACTOR_Advanced_Data_Compression.pdf ↩
"More on comparisons of digital HF modes". News. PACTOR. Retrieved 1 September 2010. http://www.pactor.com/compare.shtml ↩
"Technical details on the Pactor-IV protocol". p4dragon.com. PACTOR IV. Archived from the original on 23 October 2015. Retrieved 25 November 2022. https://web.archive.org/web/20151023162156/http://www.p4dragon.com/en/PACTOR-4.html ↩
"Summary on SCS Waveforms" (PDF). SCS. Spezielle Communications Systeme GmbH & Co. KG. Retrieved 1 June 2021. https://www.scs-ptc.com/download/SCS_Waveforms_Emission_Designators.pdf ↩
"Characteristics of systems operating in the amateur and amateur-satellite services for use in sharing studies" (PDF). International Telecommunication Union. 2017. ITU-R M.1732-2. https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1732-2-201701-I!!PDF-E.pdf ↩
The PACTOR-3 Protocol (PDF). Spezielle Communications Systeme GmbH. https://www.p4dragon.com/download/PACTOR-3%20Protocol.pdf ↩
"Characteristics of HF radio equipment for the exchange of digital data and electronic mail in the maritime mobile service" (PDF). International Telecommunication Union. 2021. ITU-R M.1798-2. https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1798-2-202102-I!!PDF-E.pdf ↩
The PACTOR-4 Protocol (PDF). Spezielle Communications Systeme GmbH. https://www.p4dragon.com/download/PACTOR-4%20Protocol.pdf ↩
"A brief guide to the elements of Winlink 2000". Winlink 2000. Archived from the original on 12 May 2008. Retrieved 25 November 2022. https://web.archive.org/web/20080512053510/http://www.winlink.org/node/12 ↩
"Original request to FCC for Pactor I in Amateur Radio by ARRL". 1995. https://www.fcc.gov/document/amendment-part-97-digital-codes ↩
"Pactor I open source published in QEX, TAPR, 1994". Archived from the original on 9 November 2015. Retrieved 25 November 2022. https://web.archive.org/web/20151109104848/https://www.tapr.org/kits_an93.html ↩
"Downloads". www.scs-ptc.com. Archived from the original on 25 March 2018. Retrieved 25 November 2022. https://web.archive.org/web/20180325055429/https://www.scs-ptc.com/de/Downloads.html ↩
"PMON". www.scs-ptc.com. Retrieved 28 November 2024. https://www.scs-ptc.com/pmon.html ↩
"Update Info DR7X00 vers. 1.17". p4dragon.com. Archived from the original (PDF) on 14 June 2020. Retrieved 25 November 2022. https://web.archive.org/web/20200614235942/https://www.p4dragon.com/en/PMON.html ↩