What is the time diversity reception...

What is the time diversity reception interval for a VHF-DSC call?

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🔍 Key Concepts

• VHF-DSC (Very High Frequency – Digital Selective Calling) timing and structure of a call • The idea of time diversity in digital communications (sending the same information more than once, separated in time) • Typical symbol / bit duration and frame length used in VHF-DSC messages per ITU standards

💭 Think About

• Think about why time diversity is used in DSC calls. How long does the system wait between repeated information so that fading or interference is unlikely to affect both transmissions the same way? • Consider which of these time intervals seems consistent with very-short digital bursts on a VHF channel rather than long voice transmissions. • Compare the answer choices: which are simple fractions or multiples of a base timing unit (for example, related to 1/15, 1/25, or 1/30 of a second)?

✅ Before You Answer

• Verify in the current ITU-R M.493 (or latest DSC specification) the defined time diversity interval for VHF-DSC calls. • Check that the chosen interval is consistent with typical DSC symbol rates (e.g., 1200 baud) and frame structures; the interval should correspond to a practical number of symbols or frames, not a random value. • Confirm that maritime exam prep materials for GMDSS/VHF-DSC use the same numerical value for the time diversity reception interval.

🔍 Key Concepts

💭 Think About

✅ Before You Answer