Phonetic alphabet
Every VHF operator must know it by heart.
Numbers
Numbers are pronounced individually. "Channel 16" is spoken as "channel wun six", not "channel sixteen".
Procedure words
Procedure words (prowords) have specific meanings in marine radio communication. Using them correctly keeps transmissions clear, brief, and unambiguous.
MAYDAY
Distress signal. Used when there is grave and imminent danger to a vessel or person and immediate assistance is required. Repeated three times at the start of a distress call.
PAN PAN
Urgency signal. Used when there is an urgent situation but no immediate danger to life or vessel. Repeated three times. Pronounced "pahn pahn".
SECURITE
Safety signal. Used to broadcast navigational or meteorological warnings. Repeated three times. Pronounced "say-cure-ee-tay".
OVER
I have finished my transmission and I expect a response from you. Never use "over" and "out" together.
OUT
I have finished my transmission and no response is expected or required. This ends the exchange.
ROGER
I have received and understood your last transmission. Does not mean "yes" — only that you heard the message.
SAY AGAIN
Please repeat your last transmission. Never say "repeat" on marine VHF — in naval usage, "repeat" means fire again.
I SPELL
I am about to spell a word phonetically. Used before spelling out names, call signs, or any word that might be misunderstood.
CORRECTION
I made an error in my last transmission. The correct version follows.
RECEIVED
I have received your transmission. Similar to Roger but often used in acknowledgement of instructions.
CONFIRM
Please verify that the following information is correct, or: I confirm that the information is correct.
STATION CALLING
Used when you hear a call directed at you but did not catch the caller's identity. "Station calling [your vessel name], say again."