Marine VHF Radio

Marine VHF radios

Marine VHF radio Do not leave the dock without one. Every boat should be equipped with a marine VHF radio, this is not a requirement but it is smart. Some would say in this day and age you could use a phone. But do you know the Coast Guards number if you need help. Do you know the phone number of the boat half a mile away?

VHF radios are invaluable and with Digital Selective Calling (DSC) we have even more benefits. A DSC equipped VHF radio can send your exact position to rescue services or indeed anyone within VHF range. Rescue can be minutes away if you press that little red button, more on DSC later.

Every recreational boat should be equipped with a marine VHF radio, as we stated before this is not mandated but it is wise. VHFs are the prime means of communications in local waters i.e. up to 20 miles offshore see range.

Marine VHF radios
Marine VHF radios

With a VHF you can talk to someone on your own boat, you can talk to another boat, you can call for help, you can listen for maydays, listen to weather alerts, and you can call a ship to help maneuvering in a channel. With an AIS signal you can find the radio call sign of a ship and call them by name.

VHF radios can be Entry level radios with just the basics, for around $100, or you can look for additional features like;

  • Dual or multi station
  • DSC capability
  • Connect to Chartplotter
  • AIS integration
  • Remote mic
  • Hailer
  • GPS
  • Wireless remote

VHFs are for use in and around the water not for use on land. If you want to use the VHF like a walkie-talkie? Then choose one with family radio service (FRS). Standard Horizon HX-471S has FRS channels and can be used on land and water.

Marine VHF Range

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Shakespeare

How far can you expect your radio to reach? The International Maritime Organization stipulates VHF range as; Area A1 ; Within range of VHF coast stations with continuous DSC alerting available (about 20-30 miles)

Whether you can receive 30 miles offshore is another question and depend on your equipment and weather conditions. VHF stands for very high frequency between 156 and 174MHz. VHF signals travel in straight lines (line of sight) and so range is relatively small.

Features that control range; Radio power and Antenna performance

  • Transmitter Power
  • Loss in cable to Antenna
  • Transmit Antenna Gain
  • Path Loss
  • Receive Antenna Gain
  • Loss in cable to Receiver

You can see features on both sides of the antenna influences the quality of reception and broadcast

Power; Under average conditions, a 25 watt radio with an 8-foot antenna, range should be within a 12 to 15 mile radius. Weather is the limiting factor. Fixed location radios have a selector switch which alternates between 1- to 25-watts of power, which is an obvious advantage over the lower power of handheld units.

Batteries and range; Unless you need the range, set your VHF to minimum power, this will save your battery. “typical operation” of a VHF is normally defined as 5% transmit, 5% receive, and 90% standby.

VHF Antenna; It does not matter how much power you have in the radio, if your antenna is too close to the deck. Mount the antenna as high as possible and make it vertical.

Antenna Gain; Gain in a VHF Marine antenna is expressed in decibels (dB). Typically marine antennas are 3, 6 or 9DB. The 3 l ie low gain antenna means equal energy distribution in all directions. A 9db antenna has most energy focused 90 degrees to the antenna. Assuming a vertical antenna which is best the 3DB is best for a sailboat, due to heeling and the 9DB is best for powerboats.

Here a resource on Antenna from Boat Project

Handheld or fixed

Handheld VHF radios
Handheld VHF radios

Choosing a marine VHF radio either a handheld or fixed radio depends on your intended use and the features of the boat. If you are looking for the longest range a fixed mount radio is best. If portability is an issue a handheld is best.

Handhelds are limited to a transmit power of 1-6 watts. For normal handheld use from a small boat due to the low antenna range maybe 3-5 miles. Both the power and antenna height of a fixed mount radio extends this range dramatically

Fixed Mount VHF radio

  • Higher Power up to 25 watts
  • With a high antenna, fixed radios have the best range
  • Fixed radios have full DSC
  • Additional features can be added like AIS
  • Power to vessels 12V system
  • Remote mic or wireless mic
  • Hailer

Handheld VHFs

  • Handheld radios have less power
  • Since the antenna is on the radio, range is limited
  • Handhelds these days can be waterproof and floating.
  • Cost effective
  • Some handhelds