SITOR (SImplex Teletype Over Radio) is a system for transmitting text messages. Although it uses the same frequency-shift keying (FSK) modulation used by regular radioteletype (RTTY), SITOR uses error detection, redundancy, and/or retransmission to improve reliability. There are two SITOR modes: SITOR sends 7-bit characters as a bit stream at 100 baud (which, in this case, is 100 bits per second, 10 milliseconds per bit, or 70 milliseconds per character). The bitstream is FSK modulated with a 170 Hz frequency shift. The high frequency is a mark, and the low frequency is a space.
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| - SITOR (SImplex Teletype Over Radio) is a system for transmitting text messages. Although it uses the same frequency-shift keying (FSK) modulation used by regular radioteletype (RTTY), SITOR uses error detection, redundancy, and/or retransmission to improve reliability. There are two SITOR modes: SITOR sends 7-bit characters as a bit stream at 100 baud (which, in this case, is 100 bits per second, 10 milliseconds per bit, or 70 milliseconds per character). The bitstream is FSK modulated with a 170 Hz frequency shift. The high frequency is a mark, and the low frequency is a space.
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Description
| - Listen to a sample of a SITOR idler pattern, from the U.S. Coast Guard station NMC . The letterns "NMC" are also transmitted in Morse.
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abstract
| - SITOR (SImplex Teletype Over Radio) is a system for transmitting text messages. Although it uses the same frequency-shift keying (FSK) modulation used by regular radioteletype (RTTY), SITOR uses error detection, redundancy, and/or retransmission to improve reliability. There are two SITOR modes:
* SITOR-A is used for point to point links. SITOR-A uses automatic repeat request (ARQ) to gain reliability. If the receiver detects an error, it requests a retransmission.
* SITOR-B is used for broadcast links. SITOR-B transmits each character in a message twice to gain reliability. If the receiver detects an error in the first character, it uses the copy. If both characters are garbled, the receiver won't know what was sent. SITOR is said to use forward error correction (FEC). SITOR sends 7-bit characters as a bit stream at 100 baud (which, in this case, is 100 bits per second, 10 milliseconds per bit, or 70 milliseconds per character). The bitstream is FSK modulated with a 170 Hz frequency shift. The high frequency is a mark, and the low frequency is a space.
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