Which emission is used for distress and calling voice frequency on MF bands?

Which emission is used for distress and calling voice frequency on MF bands?

• A. J3E Single sideband telephony
• B. J2B
• C. F3E
• D. A3E

Answer: (A)

The sound part of this question is about voice communications on MF maritime channels. For distress and calling voice on MF bands, the standard emission is single-sideband telephony. This mode, designated for voice with a suppressed carrier, uses much less bandwidth than traditional AM and is more spectrum- and power-efficient for long-distance voice communications. That makes it the preferred choice for calling and distress on MF, because it preserves intelligibility under fading and interference while leaving room for more users on the same band. Other emissions listed are Morse-oriented (J2B), FM voice (F3E) which is typical of VHF/UHF rather than the lower MF bands, or AM with a full carrier (A3E), which is less spectrally efficient for long-range MF voice. Hence, single-sideband telephony best fits distress calling on MF.

The sound part of this question is about voice communications on MF maritime channels. For distress and calling voice on MF bands, the standard emission is single-sideband telephony. This mode, designated for voice with a suppressed carrier, uses much less bandwidth than traditional AM and is more spectrum- and power-efficient for long-distance voice communications. That makes it the preferred choice for calling and distress on MF, because it preserves intelligibility under fading and interference while leaving room for more users on the same band.

Other emissions listed are Morse-oriented (J2B), FM voice (F3E) which is typical of VHF/UHF rather than the lower MF bands, or AM with a full carrier (A3E), which is less spectrally efficient for long-range MF voice. Hence, single-sideband telephony best fits distress calling on MF.