Advice on buying a VHF radio

by admin


 Looking for a new or replacement VHF this summer, then look no further. We have them all listed and offer some advice on what you should look for when buying either a fixed or handheld VHF. 

Thanks to Tim Burdon -West Marine Advisor

The first decision is fixed or handheld. Both do the same job but some do it better than others. Secondly, just how much do you want to spend? With so many makes and models to choose from it is easy to base the decision on dollar values rather than performance values. You also need to look at what functions and features the VHF unit you are considering has. If it’s a handheld, does it float? If it’s fixed does it have secondary station options? Is it  AIS and GPS compatible. Also a fixed VHF radio is only as good as the aerial attached to it. In the case of handhelds, you have little choice, although most can now be linked up to fixed aerials as well to enhance their power.

VHF (Very High Frequency) radios provide two-way communication and have a range of 5 to 30 nautical miles. They are, arguably, the most important safety item onboard your boat, and are far more reliable than a cell phone, with its limited on-water range and dropped calls. In coastal or inland waters, a VHF radio is generally the fastest link to rescuing agencies like the Coast Guard, a towing service or the harbourmaster. Other uses include conversing with other boaties, listening to weather information and alerts.

Handhelds are limited to a transmit power of six watts, compared to 25 watts for fixed-mount radios. Remember, VHF range is more dependent on antenna height and antenna gain than on transmit power, so you can add significantly to your range by connecting an external antenna or by transmitting from the highest location available. For normal handheld use (at five-watt transmit power), figure on a 3-8 mile range from a small boat.

The batteries in handhelds vary in capacity from about 500mAh to 2000mAh, and the current draw on high-power transmit can be in the two-amp range. This quickly depletes a battery if there is lots of conversation.

Unlike Single Sideband (SSB) or shortwave radios, VHF radios transmit and receive line of sight signals. Mountains, land masses, the curvature of the earth or anything else that blocks vision in a straight line will also block VHF signals (although they do have the ability to “bend” around objects in a limited way).

VHF radios only listen to the strongest signal they receive. If several people are transmitting simultaneously on the same frequency, you will only hear the one with the strongest signal, which will “step on” the other weaker transmissions.

Maximum Power

Fixed-mount radios are legally limited to 25 watts of transmit power. All have the option of transmitting at one watt of power so that short-range conversations are less likely to interfere with large numbers of boaters. It’s a good idea to try to reach your party on one watt before switching to 25 watts.

All VHF radios have the same 55 channels with International menus and you can listen to any of them, but most are reserved for government, commercial shipping or Coast Guard use. You can transmit on about 12-15 channels.

Your antenna installation is the most important variable affecting the operating range of your VHF. Mount your antenna as high as possible and use an antenna with 6 or 9dB gain. Use large-diameter, low-loss coax cable with properly installed connectors and run it as directly as possible to the radio.

Battery Power

Fixed VHF radios receive power from your boat’s battery bank, so your operating time is essentially unlimited, because they draw about half an amp while receiving, and about five amps while transmitting at maximum 25 watt power. The only problem is that, if your battery system goes dead, so does your VHF radio. A handheld VHF is thus an important backup in an emergency.

A hand held VHF will operate for a range of between 7 ½ and 20 hours. Battery life depends on the radio’s physical size, which determines just how big of a battery it will hold, whether it transmits at 5 or 6 watts on the high power setting, and if the battery pack also powers a GPS receiver. In general, floating VHFs have shorter battery life than heavier, non-buoyant models. What matters most is the answer to this question; will the radio operate all weekend without a recharge?

Digital Selective Calling (DSC)

All fixed VHF radios include Digital Selective Calling capability, which is part of the international protocol of safety procedures in the Global Maritime Distress Safety System (GMDSS). DSC provides handy non-emergency functions, allowing you to communicate individually with another boat or group of boats. You can privately send and receive positions (referred to as Position Request or Position Polling) with your buddy boats to rendezvous at that secret location where the fish are biting, for example.

What’s more important are DSC’s emergency capabilities—functioning like a sort of coastal EPIRB. In an emergency, one push of a button makes your radio send an automated digital MAYDAY message on VHF Channel 70, which can be received by all other vessels within radio range and the Coast Guard. It transmits your vessel ID number, called an MMSI Number, as well as your position and the nature of your distress call (undesignated, fire, flooding, collision, grounding, capsize, sinking, adrift, abandoning, piracy, MOB). The radio then automatically switches to Channel 16 for voice communication after this information has been sent, allowing you to communicate by voice with would-be rescuers.

All DSC radios sold in March 2011 or later (Class D radios) have a separate “watch standing” receiver that constantly monitors DSC Hailing Channel 70. The radio’s other receiving channel is free to listen to any other channel. Radios built to these standards also include additional features including added memory to store other vessels’ MMSI numbers. Older radios may only have one receiver (so you could possibly miss an emergency call while listening on a different channel) or may not have DSC at all.

VHF Radio Size and shape

Typical fixed compact units measure about 6″ wide x 3″ tall x 5-6″ deep and are designed to fit in the or around the helm. Standard Horizon makes two of the smallest. The cases on the GX1700 and GX1600 are only about 3 1/2″ deep, so they’re a good choice for a small boat.

Black box designs like ICOM’s M400BB and Garmin’s VHF 300 are another space-saving alternative, with a modular design that positions the guts of the radio in a remote, sheltered location, with only a small handset and speaker panel taking up your valuable space on a crowded instrument panel.

A key advantage of a handheld is they are small and can be place just about anywhere.  The portability means you can communicate while you are away from the primary helm and you can link to the mother ship from your dinghy and let you summon assistance when the outboard fails to start.

Another advantage of being portable and ‘of no fixed abode’ is if your electrical system fails and your fixed VHF is powerless, then  the handheld with its own separate antenna and battery pack will still be fully functional.

If your handheld radio goes overboard, a floating handheld gives you another chance to avoid a big disappointment and a trip to the store for a new radio. Although floating radios are a relatively recent idea, most of the handheld radios today now float. Note that there seems to be a trade-off between lightweight, floating radios, and radios with big batteries and the longest battery life, so you have to choose which feature, long runtime or a floating radio, you prefer.

Some handhelds also include  a “Float ’n Flash” feature. These radios float face-up, and the screen, buttons and several LED lights on the base all flash on and off.

GPS or AIS combos

Several radios include a built-in GPS receiver, which you can use for navigation, providing your Lat/Lon position and allowing you to navigate to stored waypoints. These VHF/GPS combos include Digital Selective Calling (DSC), which functions as a sort of VHF-frequency emergency beacon. Just push and hold down the red DISTRESS button, and it sends an automated digital distress message to the Coast Guard and all other DSC radio-equipped vessels. Rescuers instantly know who you are, where you are (using GPS coordinates), the name of your boat and the phone numbers of your emergency contacts.

DSC also provides non-emergency capabilities, allowing you to communicate individually with another boat or group of boats using MMSI numbers. You can send and receive each other’s positions as well, if your radio and the other vessel’s radio are interfaced to GPS.

Scanning Functions

Virtually all radios now have several scanning options, so this has ceased to be a reason to buy one radio over another. There are variations on this theme, however, and you should become familiar with the terminology.

Dual Watch or TriWatch allows you to monitor a working channel, like VHF Channel 72, and then pop back to VHF Channel 16 to check for traffic every two seconds or so. This is related to the requirement that mariners maintain a watch on Channel 16 so they can go to the aid of someone broadcasting a Mayday, as well as to listen for their vessel being hailed by another boater. TriWatch adds VHF Channel 9 to the scan list, which can be a hassle in areas where VHF Channel 9 is used for fishing chatter. In any case, virtually all radios have Dual and/or TriWatch.

Tag Scan allows you to select any number or combination of channels to monitor. Most radios also offer this feature.

Measuring VHF receiver performance

Lots of boats are on the water and in some areas boaters have difficulty finding a clear frequency, with interference from signals on adjacent channels making it hard to hear messages. Some radios offer better performance in filtering out RF signals, referred to as intermodal rejection, or how well the radio hears only what it is supposed to hear. Generally, modern VHF radios have increasingly sensitive receivers.

Another problem happens when boaties near you can pick up distant signals, but you can’t. Assuming that your antenna, cable and coax connectors are in good working order (and with corrosion in a salt-water environment, this is a big assumption), you may have a problem with the sensitivity of your receiver, how well the radio hears or how strong the signal must be to be heard.

Sensitivity is measured in microvolts (µ[email protected] 12dB SINAD), and smaller numbers are superior. Remember that the type and quality of your antenna and its height above the water are the most important factors in receiver performance.

Antenna adapters for your VHF are available to connect your handheld to the ship’s antenna. This extends the range of the handheld dramatically, and is an important safety feature should your fixed radio fail. The type of adapter varies with the brand of radio: most use a BNC connector, while others use a special connector. All provide male PL-259 threads for connection to the antenna coax cable.


HOW TO USE A VHF – Courtesy of Maritime NZ

With a VHF radio, calls can be received by Maritime NZ, the Coastguard and by vessels which may be in position to give immediate assistance. A VHF marine radio also helps ensure that storm warnings and other urgent marine information broadcasts are received.

There is good VHF radio coverage in the coastal waters of New Zealand.

Off coastal water, a VHF radio should be your first communication in an emergency. With a few exceptions, even a portable VHF radio can give you up to 50kms of coverage. Even better, on channel 16, a trained operator will take your emergency call within a minute and begin co-ordinating your rescue. Channel 16 is known as the distress channel. Be aware though that a VHF has a range limit and is subject to shadows in difficult terrains like Fiordland.

Four simple steps

Follow these four simple steps to make sure that your VHF radio is ready in an emergency.

Get the right VHF radio for you

The best advice is for skippers to always have a handheld, waterproof VHF radio on their person, preferably attached to their life jacket. A fixed VHF radio has a greater range and is better for regular communication, but you will not be able to access it if it’s water damaged in a capsize. Carry both a handheld and a fitted VHF radio on your vessel.

Take a course

Knowing how to use a marine VHF radio correctly and with confidence is vital in the event of an emergency. To operate a maritime VHF radio you are required to hold a VHF radio opertor Certificate, unless you are transmitting in an emergency or in distress. Courses are only a few hours long and give you the confidence of knowing how to use a VHF radio in an emergency.

Online courses only cost $85 and are available at CoastGuard Boating Education.

Get a call sign

A call sign for your boat is the best way of making sure each radio transmission is individually identifiable. It is registered on a national search and rescue database. This means that search and rescue authorities can access information about your vessel to help locate you faster in an emergency. Call signs only cost $45 and are available at Coastguard Boating Education or the Ministry of Businesss Innovation and Employment.

Know where you are

VHF radios have excellent coverage in most coastal regions. Many inland waterways are less reliable. Before going boating ask a local boatie or Coastguard, they will know where there is no or little VHF coverage. Also check the VHF coverage map.

If the area you’re boating in doesn’t have good coverage, make sure you have an EPIRB (a distress beacon for boats), or a waterproof PLB (personal locator beacon) and a cellphone. In fact, it’s always a good idea to have a beacon anyway.

Using your VHF

Other than being in standby, Channel 16 is for hailing and distress purposes only, which in some areas, seems to be a long-forgotten rule! So make your initial hailing call clear and short!

The correct hailing procedure is to state one to three times in succession the name of the boat or station you are calling, followed once or twice by the name of your boat, then “Over.” Any additional words are unnecessary and incorrect procedure. Once your party replies, you instruct him/her to switch to a working channel and clear out of channel 16.

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