🔍 Key Concepts

• MF-HF maritime voice uses single-sideband (SSB) radiotelephony, not simple AM like broadcast radio • Standard international channel spacing for marine MF-HF voice is set by ITU (International Telecommunication Union) to fit typical SSB bandwidth • Think about the usual audio bandwidth of a voice SSB signal (roughly 2.4–2.7 kHz) and what channel spacing is needed to avoid overlap

💭 Think About

• If a voice SSB signal needs about 2.4–2.7 kHz of bandwidth, which of the options would reasonably separate adjacent channels so they don’t interfere? • Compare each choice to typical SSB voice bandwidth: which value is too small to prevent overlap, and which ones are unnecessarily large for efficient spectrum use? • Ask yourself: which spacing value is most commonly associated with marine SSB channels in GMDSS MF-HF equipment?

✅ Before You Answer

• Eliminate any option that is clearly too narrow to prevent adjacent-channel interference for a ~2.5 kHz-wide SSB signal • Eliminate any option that is much wider than needed, since regulators try to pack channels efficiently • Recall that most modern MF-HF marine transceivers step channels by a standard ITU spacing value—match that figure to the closest choice