Why Is The Height Of A VHF Radio Antenna Important

VHF Radios: How to Optimize Performance for Clear, Reliable Communications

When temps start to rise, and everyone wants to have fun in the sun, owning a boat can be a great way to cool off and enjoy an adventure with family and friends. You can get a great deal, especially near the end of a model year, and given the variety of different financing adventures, owning a boat might be more affordable than you think. Even if you can’t afford a bigger boat, a used outboard motor can turn a simple rowboat into a craft that’s sure to be at the heart of your family’s summer lifestyle for years to come. However, as any seasoned boat owner can tell you, the right equipment is the cornerstone of maritime safety.

What is a VHF radio, and why do I need one?

A VHF radio is the centerpiece of your boat’s safety gear. VHF stands for very high frequency and refers to the wavelength of the signals these kinds of radios emit. Their longer wavelength signals can travel farther than UHF (ultra-high frequency) signals, so they are predominantly used outdoors. Groundskeeping crews or security guards patrolling outside an arena might use VHF radios to stay in contact with one another. They’re also popular on golf courses and widely used in aviation and boating.

In case of a maritime emergency, a VHF radio is your best option for getting help. In fact, although federal boating regulations don’t include VHF radios on their list of required equipment, most insurers strongly advise boat owners to keep a VHF radio on board, understand how to use it, and ensure it is functioning properly by including it in a pre-launch checklist.

Additionally, VHF radios are a convenient, effective way of communicating with other boaters in non-emergency situations. Whether you want to warn a nearby boat about potentially hazardous conditions, ask a question about local communities onshore, or get information about a nearby marina, your VHF radio keeps you in touch with your fellow boat captains.

Getting to Know Your VHF Radio

Whether you have a powerboat, pontoon, or fishing boat, being familiar with the key components of your VHF radio is an important aspect of operating your watercraft safely and responsibly. If you understand how your radio works, you’ll be more comfortable using it, and if it should malfunction, you’ll be better prepared to troubleshoot the problem.

Your VHF equipment might be stationary, with a radio and a separate hand-held microphone, or portable, with radio, microphone, and all other components contained in a compact, handheld unit. Generally, the following parts comprise a VHF communication system:

  • A power source. Stationary units are hard-wired to the boat’s power, while portable units run on batteries
  • The radio unit, which contains a receiver and a transmitter that allow you to send and receive signals. The radio features and an LCD which shows the current volume and channel as well as other information (for example, battery life in the case of portable models). It also has controls that allow you to use the radio: for example, you can select the channel, adjust the volume, switch between receiving and transmitting, and so on.
  • The antenna, which extends the receiver’s ability to pick up signals. Best practices call for keeping a backup antenna on board in case your main antenna is damaged
  • A DSC controller, which gives your boat a unique digital identifier called an MMSI or maritime mobile service identity. The DSC controller also handles distress calls
  • An automatic identification system (present in more advanced units) that uses a GPS receiver to transmit location coordinates and other information such as destination and MMSI.

For Optimal VHF Radio Performance, Do These Things

Nothing affects the performance of your VHF radio more than antenna height. This because VHF waves travel in a straight line and become weaker over greater distances. For communications to be effective, the receiving antenna must be able to “see” the waves coming from the transmitting antenna. The greater the distance between the two antennas, and the more obstructions between them, the harder it is for the signal to get through. In light of these characteristics, VHF is often called “line of sight” or “LOS” communication.

If trees, buildings, or even natural features of the Earth, such as cliffs or canyons are in the way, transmitted messages may not arrive at the receiver, or may be difficult to hear or understand. In some environments, radio waves can be reflected by mountains or buildings, such that the receiving antenna picks up the different components of the wave at different times. It’s a phenomenon called multi-path propagation, and it can render the radio signal useless and unintelligible.

To overcome these factors, mount your antenna as high as possible. The higher the antenna, the less likely it is that objects will interfere with the radio’s signal. Depending on the design of your vessel, you may be able to mount the antenna on the roof of the cabin, on a mast, or on the helm.

Other factors you should consider include the length of the antenna: longer antennas perform better than shorter ones. Additionally, transmitter power directly impacts your signal: the more power, the farther your signal can reach. Consumer VHF equipment has a maximum transmitter power of 25 watts. It’s also important to make sure your antenna is perfectly vertical. If it leans at all, your radio signal won’t travel as far.

To estimate the range of your radio at a given antenna height, multiply the square root of your antenna’s height (in feet) by 1.2246 to get the distance (in nautical miles) you can expect your VHF radio signal to travel.

In addition to antenna height, keep these things in mind to make sure your VHF radio performs properly.

  • The radio should be located out of direct sunlight, away from engine noise and vibrations that might make it hard for you to hear or for others to hear you.
  • Mount the radio at least three to four feet away from magnetic or electronic compasses and other electromagnetic devices, as these are another potential source of interference. If using a hand-held radio, move as far away from electromagnetic devices as possible while sending and receiving.
  • The U.S. Coast Guard has found that light-emitting diode (LED) lighting can interfere with digital selective calling and automatic identification systems, so be sure your antenna and radio are mounted away from navigation lights, floodlights, searchlights, and similar LED-based equipment. The Coast Guard has published procedures for testing your VHF radio equipment to determine whether LED interference is a problem
  • Make sure your radio is easy to reach and that the controls are visible.
  • Periodically inspect your antenna for signs of corrosion and wear, and check the cabling for weathering, kinks, and frayed insulation.
  • Make sure your radio is properly connected to an adequate power supply, using the proper type a gauge of wire. Use fuses or breakers where appropriate, and if in doubt, consult a professional installer or electrician.

Wrapping It All Up

New boat prices may be lower in the spring, just before the new model year begins. Check online listings and hobbyist publications for current power boat, fishing boat, and sailboat prices, as well as great deals on other kinds of watercraft.

Read up on maritime safety, take a state-approved safety course, and keep the right equipment – including a VHF radio – on your boat. Run through a checklist before you set out to make sure everything’s working.

Finally, install your radio in a place where it’s easy to reach, visible, and isolated from engine noise, direct sunlight, and electromagnetic devices. For best results, mount your VHF radio antenna on the highest point of your boat.