A VHF is simple to work once you know what each control does and what the set needs: a healthy supply, a sound antenna and a clear voice. Most "faults" on a charter yacht turn out to be a knob in the wrong place.
1 · The controls
What each knob and button does
How do I set the squelch on a VHF radio?
Turn the squelch down until the hiss starts, then up until it just stops. Set it any higher and it shuts out weak stations too, so you hear nothing for hours.
A fixed set has few controls. Volume sets how loud you hear others; it changes nothing in what you send. Squelch mutes the hiss between calls: turn it down until the hiss starts, then up until it just stops. Set any higher, it shuts out weak stations too, and you hear nothing for hours.
The 16 key takes you straight back to channel 16. The red DISTRESS button sits under a cover and sends a DSC alert: never press it to try it. Dual watch listens to 16 and one channel you choose; tri-watch listens to 16 and two others in turn.
Rule
Squelch: just past the point where the hiss stops.
2 · Power and supply
25 watts to reach, 1 watt close by
Should I use 25 W or 1 W on my VHF?
Use 25 W for range in open water and 1 W in harbour or to a boat nearby; the H/L key switches between them. If a distant station does not answer, check you are not still on 1 W.
The H/L key switches between high power, 25 W, and low power, 1 W. Low power is for short range: inside a harbour, to a boat nearby. If a station miles away does not answer, check first that the set is not still on 1 W.
High, 25 Wopen water, long range
Low, 1 Win port, close by
The set lives on the yacht's battery. A blank display means no supply: check the VHF breaker on the switch panel, the fuse and the battery switch. A tired battery still lights the display but cannot give full power when you transmit, so others hear you weak. Run the engine to charge it, then call again.
3 · Antenna and range
Height gives range
Does antenna height or transmit power matter more for VHF range?
Height matters more than power: VHF travels roughly in a straight line, so a masthead antenna reaches much further than one on the pushpit rail, about 10–20 miles to another yacht.
VHF travels roughly in a straight line, so each antenna must "see" the other over the horizon. Height matters more than power: an antenna at the masthead reaches much further than one on the pushpit rail, and a coast station on a hill reaches furthest of all.
Between
Roughly
Two yachts with masthead antennas
10–20 miles
A yacht and a coast station on a hill
the longest: 30 miles and more
A handheld at deck level
a few miles
The cable is part of the antenna. A corroded connector at the mast foot loses most of the signal: range falls to a mile or two until you clean or replace it. And never transmit with the antenna unplugged: the power has nowhere to go and can damage the set.
4 · The handheld
Short range, but it goes with you
How far will a handheld VHF reach, and how do I get the most from it?
Only a few miles: a handheld gives about 5 W from a short antenna at deck level. Stand up on deck, hold the antenna straight up and use high power.
A handheld gives about 5 W from a short antenna at deck level, so it reaches only a few miles. Give it its best chance: stand up on deck, hold the antenna straight up and use high power. Offshore, the fixed set is the one that reaches the coast.
What
Fixed set
Handheld
Power
25 W / 1 W
about 5 W / 1 W
Antenna
at the masthead
on the set, at deck level
Supply
the yacht's battery
its own battery
Place
the main radio
dinghy, back-up, liferaft
Its strength is that it works away from the yacht: in the dinghy, and in the liferaft, so it belongs in the grab bag. Transmitting drains the battery fast: charge it before you leave. IPX7 means it survives a short dunking, about 1 m for 30 minutes. It does not mean it floats.
5 · Microphone technique
Press, pause, speak
Why are my first words cut off when I talk on the VHF?
The set needs a moment to start sending: press, pause, then speak. Hold the microphone a few centimetres from your mouth and speak in a normal voice.
You talk and listen in turn: press the button on the microphone to transmit, release it to listen. The set needs a moment to start sending, so press, pause, then speak, or your first words are clipped.
Hold the microphone a few centimetres from your mouth and speak in a normal voice: shouting with it against your lips distorts every word.
In a strong wind, shield the microphone with your hand or your body.
Release the button when you finish. A handheld jammed in a locker with its button pressed transmits non-stop and blocks the channel for everyone.
To test the set, ask a marina or another boat for a radio check on a working channel, never on 16 or 70.
Rule
Press, pause, speak. Release to listen.
Practice questions
Questions from this topic, as the app asks them. Open one to see the answer.
Your VHF since lunch
Squelch: turned fully up
Volume: half way
Power: 25 W, channel 16
Not a sound for three hours
A friend says he called you twice this afternoon, but you heard nothing. What is the most likely reason?
Half volume mutes stations more than 5 miles away
The squelch is so high that weaker signals cannot open it
The 25 W setting drowns out stations that call you
Channel 16 stays silent unless DSC is switched on
Show the answer
B. The squelch is so high that weaker signals cannot open it
Squelch turned right up cuts out everything but strong signals; back it off to just past the hiss.
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.
