Module 2 - VHF Radio Basics
Power, Squelch, and Volume
What you will learn
Distinguish transmit power, receive volume and squelch, then set each control for the real task without assuming one control can fix another.
Transmit power affects the strength sent from the radio; volume affects how loudly received audio is heard; squelch sets the threshold below which receiver noise and weak signals are muted.
Volume changes received loudness, not transmit range. Set it so a call can be heard above the cockpit, engine or cabin noise. Turning the volume down after a call can silently end the listening watch even though the set still appears to be on.
Squelch is a receiver noise gate. On a manual control, open it until noise is heard, then close it only far enough for the noise to disappear; on an automatic or preset control, follow that radio's instructions and verify that weak traffic remains audible. Too little squelch causes constant hiss, while too much can hide a weak call.
Use low transmit power first for nearby routine communication; it limits unnecessary interference. The MCA's small-craft guidance makes distress the exception to that low-power-first habit. Power cannot repair a muted receiver, a wrong channel, a damaged antenna or a station that is out of coverage.
| Control | What it changes | Misconception to reject |
|---|---|---|
| Volume | Loudness of received audio | It does not increase transmitted range |
| Squelch | Receiver mute threshold | Maximum squelch does not improve reception |
| Low / high power | Transmitter output setting | High power cannot fix every no-reply problem |
| PTT | Receive or transmit state | Holding it does not reserve the channel |
Diagnose a silent set before reaching for high power
The display is lit and the channel is correct, but you hear no traffic and receive no reply from a nearby marina.
1. Check reception
Raise volume and verify the squelch control is not suppressing every weak signal.
2. Check transmission
Confirm the intended low/high power setting and that PTT is actually switching the set to transmit.
3. Check the chain
If silence continues, check channel purpose, antenna, position, range and whether the station is listening.
Sense check: If opening squelch produces receiver noise, the audio path is alive; that does not prove the antenna or transmitted call is effective.
Common mistake or limitation
- Turning squelch fully up to make the set sound tidy; this can suppress weak but important calls.
- Confusing volume with transmitter power; louder speaker audio does not make another station hear you farther away.
- Selecting high power for every close routine call instead of checking the complete radio path.
Recap
- Volume controls the loudness of received audio.
- Squelch mutes receiver noise below a threshold and can hide weak signals if over-set.
- Use low power first for nearby routine traffic; distress is the stated exception.
- Power is only one link in the communication chain.
Optional quick check
Section 2 of 9
The radio is quiet, but a nearby vessel says there is weak traffic on your channel. Which control should you check first?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
Continue studying VHF Radio Basics
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