A DSC Distress alert is received by your vessel and your transceiver frequency display reads: Transmit = 4207.5 kHz and Receive = 4207.5 kHz with J3E emission -- what information can you infer from this?
• DSC distress alerts on MF/HF bands (4 MHz) and their associated voice follow-on channels • Difference between DSC frequencies and radiotelephony (J3E) working frequencies • Meaning of simplex operation and how some DSC controllers auto-tune the radiotelephone after an alert
• Look at 4207.5 kHz and ask yourself: is this normally a DSC frequency, or a radiotelephone distress/working frequency associated with 4 MHz DSC? • Think about what J3E emission indicates about the type of communication you are set up for. Is that data (DSC) or voice? • Consider whether a proper DSC distress sequence would require you to manually change to a separate voice follow-on frequency, or whether many modern sets will automatically tune to the requested follow-on channel.
• Verify what the standard 4 MHz DSC distress/control frequency is, and compare it with 4207.5 kHz. • Check if 4207.5 kHz is normally used simplex for voice distress/urgency/safety in the 4 MHz band. • Confirm that the display showing J3E on 4207.5 kHz both Tx and Rx means the set has already selected a voice channel, not the DSC channel itself.
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