Physics:PACTOR

From HandWiki

PACTOR is a radio modulation mode used by amateur radio operators,[1] marine radio stations,[2] military or government users such as the United States Department of Homeland Security & its cybersecurity agency CISA,[3][4] and radio stations in isolated areas to send and receive digital information via radio.[5]

PACTOR is an evolution of both AMTOR and packet radio;[6] its name is a portmanteau of these two technologies' names. PACTOR uses a combination of simple FSK modulation, and the ARQ protocol for error detection and data throughput.[7] Generational improvements to PACTOR include PACTOR II, PACTOR III, and PACTOR IV which are capable of higher speed transmission. As PACTOR was designed to operate as a shortwave HF band radio, it commonly operates at frequencies between 3 MHz and 30 MHz.[8]

History

PACTOR (Latin: The mediator) was developed by Special Communications Systems GmbH (SCS) and released to the public in 1991.[6]

PACTOR was developed in order to improve the reception of digital data when the received signal was weak or noisy.[6] It combines the bandwidth efficiency of packet radio with the error-correction (CRC) and automatic repeat request (ARQ) of AMTOR.[7] Amateur radio operators were instrumental in developing and implementing these digital modes.[9]

Current uses

PACTOR radio equipment consists of an HF transceiver, a computer and a terminal node controller.[2] Software running on the computer drives the terminal node controller.[2][10] The most commonly used amateur program for this purpose is Airmail.[2][8]

PACTOR is used by Amateur Bulletin board system operators to exchange public messages, and open conversations across the world.[2] It is also used by the NTSD (digital) portion of the ARRL's National Traffic System (NTS) to pass digital ARRL Radiograms.[11] Newer PACTOR modes are used to transfer large binary data files and Internet e-mail, particularly via the Winlink global e-mail system.[2][8]

The SailMail network transfers e-mail on behalf of marine stations.[12]

Technical characteristics

PACTOR is a set of standardized modes used by radio operators for FSK radioteletype transfer of digital information over shortwave bands.[13][7]

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.[14]

To reduce the amount of data sent, on-line data compression is utilized, along with memory ARQ error correction.[15]

PACTOR utilizes time-division duplexing for bidirectional, half-duplex communication. To do this, it utilizes a single frequency to send and receive data by alternating transmission time, usually with 1.25 to 1.4-second cycles; this is opposed to using separate frequencies for sending and receiving data (Frequency-division duplexing).[7][16]

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).[17][18]

The International Telecommunication Union (ITU) emission designators:

  • Pactor I is 340HJ2D or 440HJ2D (at a symbol rate up to 200 symbols per second).[19]
  • Pactor II is 450HJ2D (at a symbol rate of 100 symbols per second).[19][14][20]
  • Pactor III is 2K20J2D (at a symbol rate of 100 symbols per second).[19][21][22]
  • Pactor IV is 2K20J2D or 2K40J2D (at a symbol rate up to 1800 symbols per second).[19][23][18]

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).[24]

Pactor modes other than level 1 (P1) are not open source,[25][26] but are publicly documented[27] and can be monitored and decoded easily over the air by third parties using free Raspberry Pi software ("PMON for Raspberry Pi")[28] or PMON utility on the modem itself.[29]

See also

References

  1. ↑ Bateman, Richard; Loveridge, Ben (21 April 2025). "3" (in English). HamStudy Technician License HamBook (2022-2026 ed.). HamStudy. p. 3.6. ISBN 978-1967466009. https://hambook.org/tech2022/pt1/chpt3/section-36-digital-and-video-modes/. Retrieved 11 April 2026. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Corenman, Jim (6 April 2020). "PACTOR/SSB Installation". https://sailmail.com/category/installation/. 
  3. ↑ "SHAred RESources (SHARES) High Frequency (HF) Radio Program". United States Department of Homeland Security. https://www.cisa.gov/resources-tools/programs/shared-resources-shares-high-frequency-hf-radio-program/shares-faqs. 
  4. ↑ Wood, Gary; Chua, Ken. "SCS Pactor Modems Homeland Security and Emergency Services Organizations Discount Policy". Farallon Electronics. http://www.felge.us/scsdiscount.pdf. 
  5. ↑ "SCS DR-9400 Review: PACTOR Modem for Reliable Off-Grid & Maritime Communication" (Video & Text). Ham Radio Therapy (Ham radio articles). 7 January 2026. https://hamradiotherapy.com/articles/scs-dr-9400-review/. 
  6. ↑ 6.0 6.1 6.2 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. 
  7. ↑ 7.0 7.1 7.2 7.3 "PACTOR". The National Association for Amateur Radio. https://www.arrl.org/pactor. 
  8. ↑ 8.0 8.1 8.2 "PACTOR: WHEN COMMUNICATION MATTERS, RELIABILITY IS THE ONLY THING THAT COUNTS". WiMo Antennen und Elektronik GmbH, Inc.. https://www.wimo.com/en/pactor. 
  9. ↑ Anderson, Eric (28 February 2023). "Amateur Radio Contributions Advance Radio Technology". Morse Nexus (PreppComm). https://preppcomm.com/blogs/news/amateur-radio-contributions-advancing-radio-technology?srsltid=AfmBOoqTUItbKNjyPwInz7VJ01cn0a3OcJk2-B8-mSsKZ4lKlBVAGPJA. 
  10. ↑ "PTC Plus - The PACTOR Controller" (PDF). 95 SCS GmbH. 1994. pp. 2-3, 5. https://www.p4dragon.com/download/SCS_Manual_PTCplus.pdf. 
  11. ↑ "What is the National Traffic System (NTS)?" (PDF). American Radio Relay League (ARRL®). https://www.qsl.net/mcarv/What%20is%20the%20National%20Traffic%20System.pdf. 
  12. ↑ "Sail-mail e-mail service for yachts via Iridium, Inmarsat, or SSB". http://www.sailmail.com/. 
  13. ↑ "PACTOR Packet Teleprinting Over Radio". WAVECOM ELEKTRONIK AG. http://www.wavecom.ch/content/pdf/advanced_protocol_pactor.pdf. 
  14. ↑ 14.0 14.1 The PACTOR-2 Protocol. SCS Spezielle Communications Systeme GmbH. https://www.p4dragon.com/download/PACTOR-2%20Protocol.pdf. 
  15. ↑ PACTOR-2/3/4 Advanced Data Compression. SCS Spezielle Communications Systeme GmbH. https://www.p4dragon.com/download/PACTOR_Advanced_Data_Compression.pdf. 
  16. ↑ Bakare, B.I.; Godwin, J.E. (23 December 2021). "X-Raying Time Division Duplexing (TDD) in Long Term Evolution (LTE)". American Journal of Engineering Research (AJER) 10 (12): 89-97. ISSN 2320-0847. https://www.ajer.org/papers/Vol-10-issue-12/J10125997.pdf. Retrieved 11 April 2026. 
  17. ↑ "More on comparisons of digital HF modes". http://www.pactor.com/compare.shtml. 
  18. ↑ 18.0 18.1 "Technical details on the Pactor-IV protocol". http://www.p4dragon.com/en/PACTOR-4.html. 
  19. ↑ 19.0 19.1 19.2 19.3 "Summary on SCS Waveforms". Spezielle Communications Systeme GmbH & Co. KG. https://www.scs-ptc.com/download/SCS_Waveforms_Emission_Designators.pdf. 
  20. ↑ "Characteristics of systems operating in the amateur and amateur-satellite services for use in sharing studies". International Telecommunication Union. 2017. https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1732-2-201701-I!!PDF-E.pdf. 
  21. ↑ The PACTOR-3 Protocol. Spezielle Communications Systeme GmbH. https://www.p4dragon.com/download/PACTOR-3%20Protocol.pdf. 
  22. ↑ "Characteristics of HF radio equipment for the exchange of digital data and electronic mail in the maritime mobile service". International Telecommunication Union. 2021. https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1798-2-202102-I!!PDF-E.pdf. 
  23. ↑ The PACTOR-4 Protocol. Spezielle Communications Systeme GmbH. https://www.p4dragon.com/download/PACTOR-4%20Protocol.pdf. 
  24. ↑ "Original request to FCC for Pactor I in Amateur Radio by ARRL". 1995. https://www.fcc.gov/document/amendment-part-97-digital-codes. 
  25. ↑ "Pactor I open source published in QEX, TAPR, 1994". https://www.tapr.org/kits_an93.html. 
  26. ↑ "Downloads". https://www.scs-ptc.com/de/Downloads.html. 
  27. ↑ "PMON". https://www.scs-ptc.com/pmon.html. 
  28. ↑ "Update Info DR7X00 vers. 1.17" (in en). https://www.p4dragon.com/download/Update_Info_DR7X00_Version_1_17_English.pdf. 
  • Steve Ford, WB8IMY (2001). "Chapter 5 - PACTOR". ARRL's HF digital handbook. Newington, CT: The American Radio Relay League. ISBN 0-87259-823-3. 



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