VHF (channel)

• Ch 16 — 156.800 MHz — voice distress + listening watch
• Ch 70 — 156.525 MHz — DSC distress (no voice)
• Ch 13 — 156.650 MHz — bridge-to-bridge
• Ch 06 / 67 — intership safety, SAR

MF / HF (kHz)

• 2182 voice MF · 2187.5 DSC MF
• HF DSC: 4207.5 / 6312 / 8414.5 / 12577 / 16804.5
• HF voice: 4125 / 6215 / 8291 / 12290 / 16420
• NAVTEX 518 intl · 490 nat · 4209.5 tropical

Beacons

• 406 MHz EPIRB (Cospas-Sarsat) · 121.5 MHz homing
• 9.2–9.5 GHz SART (X-band)
• 161.975 / 162.025 MHz AIS-SART · MOB-AIS

DSC alert: lift cover, hold ≥5s, follow with spoken Mayday on Ch 16.

MAYDAY MAYDAY MAYDAY
THIS IS [vessel x3]
MAYDAY [vessel]
CALLSIGN [---] MMSI [---]
POSITION [lat / lon, OR
          bearing+distance from
          a charted point]
NATURE OF DISTRESS [---]
ASSISTANCE REQUIRED [---]
[N] PERSONS ONBOARD
[other info]
OVER

Priority hierarchy

• MAYDAY ×3 — distress (grave & imminent danger)
• PAN-PAN ×3 — urgency (safety at risk)
• SÉCURITÉ ×3 — safety / nav warning

Silence: SEELONCE MAYDAY (impose) · SEELONCE FEENEE (lift). Cancel false alert: "ALL STATIONS … CANCEL MY DISTRESS ALERT OF [time UTC] OVER".

seafarerindex.com/reference/distress