SITOR

SITOR (simplex teletype over radio) is a transmission mode used to transmit textual messages akin to regular radioteletype (RTTY), but implements simple error correction.

Two modes of SITOR are used:

SITOR-A which implements automatic repeat request (ARQ) -- sometimes called AMTOR
SITOR-B which implements forward error correction (FEC)

SITOR is used commonly on shortwave bands, where it is used to transmit maritime-related information such as weather forecasts and storm warnings. In the United States, it is regularly used by the U.S. Coast Guard.

Comparisons of MT63, RTTY and HF Packet bandwidth usage

SITOR has an aurally easy to identify idling pattern. Synchronization bursts are transmitted every second or so and last for slightly more than one second. Every few sync bursts, a Morse identifier of three letters is transmitted (for example NMO in Honolulu).

SITOR idling pattern

Listen to a sample of a SITOR idler pattern, from the U.S. Coast Guard station NMC (Port Reyes). The letterns "NMC" are also transmitted in Morse.

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