Module 2 - VHF Radio Basics
Power, Aerial, And Range
What you will learn
Choose between the fixed set and handheld, and between low and high transmit power, by considering priority, range, antenna and battery—not one control in isolation.
A fixed masthead installation usually provides the stronger normal communication path; a handheld adds resilient backup. Low power is the routine starting point nearby, while distress is the explicit exception.
A fixed VHF commonly combines higher available transmitter output with a higher antenna and the vessel's main electrical supply. A handheld can continue if the fixed installation or main supply is lost, but its low antenna, battery endurance and device-specific waterproofing limit what should be expected from it.
Start nearby routine calls on low power. This reduces unnecessary interference and may be all that is needed. For distress, use the effective available means and do not let a routine low-power habit delay the alert; follow the complete distress procedure taught in the dedicated module.
High power can strengthen the transmitted signal, but it cannot restore a damaged aerial, bad connector, discharged battery, incorrect channel or screened radio path. Diagnose the whole chain and preserve the handheld's charge for the circumstances in which it may be the only working set.
Choose equipment after a main-power failure
The fixed radio goes dark after an electrical fault, while a charged handheld remains available in the cockpit.
1. Preserve communication
Use the working handheld and move its antenna to the best safe height and position available.
2. Manage energy
Keep transmissions brief, monitor battery state and use the manufacturer's approved spare or charging arrangement.
3. Address the failed link
Check the protected supply and fixed installation only when safe; do not assume the handheld has equal coverage.
Sense check: A handheld that works within a marina proves local communication, not that it can match a masthead fixed set offshore.
Common mistake or limitation
- Calling the handheld equivalent to the fixed installation without accounting for antenna height and battery endurance.
- Using high power by default for close routine traffic.
- Assuming more power cures a wrong channel, screened path or failed antenna system.
Recap
- A sound masthead fixed set is normally the primary VHF path.
- A charged handheld is valuable independent backup with shorter expected range.
- Use low power first for nearby routine traffic; distress is the exception.
- Treat power, antenna, channel and battery as one operating system.
Optional quick check
Section 6 of 9
A nearby routine call gets no reply on low power. What is the best next judgement?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
Continue studying VHF Radio Basics
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