🔍 Key Concepts
• Different emission designators used in marine radio communications (e.g., A3E, H3E, J2B, F3E)
• How modulation type (AM, SSB, FM, data/telegraphy) affects occupied bandwidth
• The idea that removing one sideband or limiting information can reduce required bandwidth
💭 Think About
• First, group each option by the type of modulation it uses (AM with both sidebands, AM single-sideband, FM, or data/telegraphy) and recall which of these is usually the narrowest.
• Think about why single-sideband (SSB) was developed compared with conventional AM for HF radio—what problem was it trying to solve regarding spectrum use?
• Consider which types of signals (voice vs. narrow-band data/telegraphy) typically need the least bandwidth in marine radio services.
✅ Before You Answer
• Identify which designator corresponds to full-carrier AM voice, which to single-sideband telephony, which to FM voice, and which to narrow-band direct-printing/data.
• Recall typical occupied bandwidth values for marine HF SSB, MF/HF AM, VHF FM, and narrow-band direct-printing (NB-DP) services.
• Before choosing, double-check which emission is specifically designed to be narrow-band for efficient use of spectrum.