PACTOR is a radio transmission protocol used by amateur radio operators, marine radio stations, and radio stations in isolated areas to send and receive digital information via radio. PACTOR is one of the fastest, most accurate, and most efficient ways to send digital data by radio. A robust network of stations that use PACTOR has been established to relay data by radio to and from the Internet, extending Internet access to sea based and other isolated users.
PACTOR (Latin for: The mediator) is a radio modulation mode that uses Frequency Shift Keyed (FSK) modulation. PACTOR was developed by Special Communications Systems GmbH (SCS) and released to the public in 1991. PACTOR is an evolution of both AMTOR and packet radio, hence the name PACTOR. It was developed in order to improve the reception of digital data when the received signal was weak or noisy. 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 (new) digital modes. PACTOR is most commonly used on frequencies between 1 MHz and 30 MHz.