Every channel has a job. A few you must know by number: 16, 70, 13 and the intership channels. The rest you look up. And whichever channel you choose, VHF reaches only as far as your antenna can see.
Can I chat with another yacht on channel 16?
No: channel 16 is for distress, urgency, safety and calling. Call the yacht on 16, agree a working channel and both move there at once; only distress traffic stays on 16.
Channel 16 is the international channel for distress, urgency, safety and calling. Under way you keep the radio on 16 even when you have nothing to say: that is how you hear a MAYDAY, a safety warning or someone calling you.
It is a meeting place, not a place to talk. You call a station on 16, agree a working channel and both move there at once. Only distress traffic stays on 16: a MAYDAY and the replies to it. While that goes on, keep off 16 altogether and make routine calls straight on the working channel: a marina's own channel, or the one your flotilla agreed beforehand.
Call on 16, talk elsewhere. During a MAYDAY, keep off 16.
What is VHF channel 70 for, and can I talk on it?
Channel 70 carries only the digital signals of DSC, distress alerts among them. Voice would block them, so the set will not let you talk there; yachts talk on intership channels such as 72 or 77.
Channel 70 carries only the digital signals of DSC, distress alerts among them: voice there would block them, and the set will not let you talk. Channel 13 is the bridge-to-bridge channel for the safety of navigation. Intership channels such as 72 and 77 are for talk between vessels. Channel 6 is intership too, but it is also used on scene in search and rescue, so leave it free.
Many sets carry an international and a USA channel plan, and some channels differ between them. Outside North America the set must be in international mode: INT, not USA, on the display.
Why can't I hear the other yacht on a duplex VHF channel?
On a duplex channel both yachts send on the same frequency and listen on the other, so each hears the coast station but not the other yacht. Ship to ship, use a simplex channel.
On a simplex channel everyone sends and listens on one frequency. While you press the button you hear nothing, and if two stations transmit together neither hears the other. So you talk in turn and end each transmission with OVER. Channel 16 and the intership channels are simplex.
A duplex channel uses two frequencies: a ship sends on one and listens on the other, and the coast station does the opposite. That suits ship-to-shore calls. Two yachts on a duplex channel both send on the same frequency and both listen on the other, so each hears the coast station but not the other yacht.
| Link | Simplex | Duplex |
|---|---|---|
| Frequencies | one for all | two: ship on one, shore on the other |
| Ship to ship | yes, in turn | no |
| Ship to shore | yes, in turn | yes |
Which VHF channel do I use to call a marina?
The marina's own working channel, from the pilot book, almanac or chart. Port and marina channels differ from place to place, so look them up before you arrive rather than guess.
| You want | Where |
|---|---|
| A yacht whose channel you do not know | call on 16, then move to 72 or 77 |
| Your flotilla, on a channel agreed beforehand | call directly on that channel |
| A marina or a port authority | its own channel, from the pilot book, almanac or chart |
| A ship that wants to agree how to pass | 13, after she calls you on 16 |
If the channel you agreed is busy, do not talk over the others: agree another free intership channel. Port and marina channels differ from place to place, so look them up before you arrive rather than guess. Near a busy commercial port, listen to its port operations or traffic channel as well as 16: you learn what the big ships are about to do.
Why can't my friend 6 miles away hear me on VHF?
High land in the way stops the signal however close you are. VHF travels roughly in straight lines, so range depends on the height of both antennas and a clear path between them.
VHF travels roughly in straight lines, like light. Two things decide whether you are heard: the height of both antennas and a clear path between them. Yacht to yacht with masthead antennas, count on roughly 10 to 20 miles over open water, not 40.
High land in the way stops the signal however close you are. A coast station on a mountain is the opposite case: its antenna is so high that it hears you from far off, while friends a few miles away behind a headland do not.
Height and a clear path give range. Land in between takes it away.
Questions from this topic, as the app asks them. Open one to see the answer.
A ship crossing ahead calls you on 16 and asks you to go to channel 13. What is 13 for?
C. Bridge-to-bridge navigation safety between vessels
Channel 13 is the international bridge-to-bridge channel for navigation safety.
Which set of channels fits these three jobs, in order?
A. 13 · 72 · 70
13 bridge-to-bridge safety, 72 intership chat, 70 DSC only.
You are under way along the coast and not talking to anyone. Which channel do you keep the radio on?
A. Channel 16, the distress, safety and calling channel
Under way, keep watch on 16 so you hear distress and safety calls and anyone calling you.
Your crew scrolls to channel 70 to call a friend, but the set will not let him talk there. Why?
B. Channel 70 carries only DSC digital calls, never voice
Channel 70 is reserved for DSC data; voice there would block distress alerts.
Your friend cannot hear you, although you are only 6 miles apart. Why?
C. VHF works roughly in line of sight, and the island is in the way
VHF travels roughly in straight lines; high land between the antennas blocks it.
You want to call a yacht you met yesterday. You do not know which channel they listen to. Where do you make the first call?
D. On 16, then move to a working channel
16 is the calling channel; once in contact, both move off it.
All 20 questions of this topic are in the app: practice by topic with the reason after every answer, your mistakes brought back, and a timed mock exam. Free, no sign-up, in the browser or in Telegram.