🔍 Key Concepts

• International aircraft distress frequencies and which are used for civil vs. military aviation • Difference between aeronautical VHF distress and maritime VHF DSC distress (Channel 70 – 156.525 MHz) • Meaning of emission designators A3E, F3E, F1B (AM voice, FM voice, digital/DSC)

💭 Think About

• First, decide which of the listed frequencies is the standard CIVIL aircraft voice distress/guard frequency used worldwide. • Then, decide which emission type is used for normal voice communication in aviation (AM vs FM; analog voice vs digital). • Eliminate any option that actually corresponds to a MARINE DSC distress channel rather than an aircraft voice distress channel.

✅ Before You Answer

• Verify which frequency – 121.500 MHz or 243.000 MHz – is the primary CIVIL aircraft voice distress frequency. • Check which emission designator represents amplitude-modulated (AM) voice used in aviation radios: A3E or F3E? • Confirm that 156.525 MHz with F1B emission is associated with VHF DSC Channel 70 (maritime digital distress/calling), not with aircraft voice distress.