What is the channel spacing for SITOR frequencies?

Official USCG Answer & Rule Citation

Correct Answer: Option A — 500 Hz

Narrow Band Direct Printing (NBDP), or SITOR, utilizes a 500 Hz channel spacing. This narrow bandwidth is highly efficient for digital data transmission, allowing multiple telegraphy channels to fit within the spectrum typically occupied by a single voice channel, optimizing the limited MF/HF frequency allocations for maritime safety and traffic.

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