Can I use a VHF antenna to receive FM radio on my boat?

Yes, a marine VHF aerial can receive FM broadcasts, but sharing it with your working VHF requires a purpose-built VHF/FM splitter with transmit protection. Reception can be usable near shore, though a separate FM aerial usually gives more predictable results and keeps the VHF installation simpler.

Check the stereo and aerial

Check that your stereo has an FM tuner and an external aerial socket, then trace the existing aerial cable. You may not need another aerial: poor reception can come from a loose plug, a damaged cable or a short wire tucked behind a metal instrument panel.

A marine VHF set cannot normally tune broadcast stations. Its channels cover marine frequencies around 156 to 162 MHz, while FM broadcasting in Britain and most of Europe uses 87.5 to 108 MHz. Both use frequency modulation, but they occupy different bands and require different receiver tuning.

Check the stereo's connector before buying parts. Broadcast stereos often use a push-in automotive aerial plug; marine VHF installations commonly use a PL-259 plug screwed into an SO-239 socket. A plug adaptor changes the connection but provides no protection against transmitted power.

Why VHF aerials receive FM

An aerial receives signals outside its intended band, though less efficiently. A marine aerial is designed for the marine VHF band, so its performance at broadcast FM frequencies depends on its internal construction.

For comparison, a simple quarter-wave element is about 48 cm long at 156 MHz and 75 cm at 100 MHz. These are approximate electrical lengths: the outer length of a fibreglass marine aerial does not reveal how its internal elements are arranged.

A masthead aerial benefits from height and a clear view towards shore transmitters. That advantage can compensate for imperfect tuning when stations are reasonably strong. It does not guarantee reception offshore, and a splitter adds some loss.

Marine VHF coaxial cable is normally 50 ohms, while broadcast receiving equipment often uses 75-ohm connections or automotive aerial arrangements. For reception, this mismatch usually matters less than aerial position, cable condition and correct connections. Follow the splitter's specified cable and connector arrangement.

Choose the right splitter

Never connect the VHF transmitter and stereo through a simple T-piece or television splitter: a transmission can damage the stereo's aerial input. A fixed marine VHF commonly transmits at 25 watts, so the splitter must explicitly support a transmitting marine VHF and a broadcast FM receiver.