I spent a lot of time researching this as it turned out to be a little more complicated than I thought. Remember that my frame of reference was my uncle’s 17′ Glastron. For that I only used a simple Standard Horizon handheld VHF radio. I have now learned that technology such as DSC and AIS have been in place for over 20 years. Where it can become tricky is determining what type of emergency system the used boat you are looking at has in place, whether it’s properly working, and if the antenna connections are good. Don’t get fixated on the impressive looking chartplotter a boat may have. The VHF unit that sits beside it deserves equal attention. Before buying another screen or radio, find out what the boat already has and whether it works. For a family-friendly 22–32 foot boat running the ICW and making occasional light offshore trips, a sound fixed VHF setup comes first. AIS can be a valuable addition, but the right choice depends on where and when you run. The information below neatly summarizes (I hope) the hardware and features that go into one of the most vital systems on a boat.
Affiliate disclosure: Some links below go to West Marine. Coastal Used Boat Guide may earn a commission if you buy through those links, at no extra cost to you. These are feature-based choices informed by published specifications and West Marine customer ratings. I have not personally sea-trialed these radios.
VHF, DSC, and AIS do different jobs
VHF is the voice radio. It lets you call another boat, a bridge tender, a marina, or the Coast Guard. A fixed-mount VHF runs from the boat’s electrical system and uses a separate, higher-mounted antenna. Its performance depends on that antenna and its cable, not just the radio at the helm.
DSC is the radio’s digital distress and calling feature. If the radio has the correct, registered MMSI number and a valid GPS position, a DSC distress alert can include the boat’s identity and coordinates. The alert has to reach a Coast Guard station or another DSC-equipped vessel within VHF coverage; it is not a guaranteed offshore message. Follow a distress alert with voice communication on Channel 16 when possible. You should never press the red distress button to test the radio or resolve an ordinary traffic situation. The Coast Guard explains DSC distress alerts here.
AIS shows information broadcast by equipped vessels. A receiver lets you see those vessels on a compatible chartplotter or on a radio with its own AIS display. A Class B transceiver both receives AIS and broadcasts your boat’s identity and position to AIS-equipped vessels in range. An AIS receiver does not broadcast your position. A DSC distress alert and an AIS broadcast are different: DSC is an emergency call; AIS is a continuing traffic-awareness signal.
Is AIS necessary on the ICW or just offshore?
For a typical private 22–32 foot recreational boat in U.S. waters, AIS is optional. The federal carriage rules apply to specified commercial and other vessels; being a large vessel alone does not mean every boat you meet will be broadcasting. AIS also misses small recreational boats that have no transmitter. Coast Guard AIS carriage information is useful if you want the details.
On the ICW, AIS reception is most useful near ports, tow traffic, and busy commercial channels. Seeing an equipped tow’s name and direction can help you understand what is approaching and make a clear VHF call. AIS signals can sometimes reach around a bend when the intervening land is low, but do not count on it as a blind-corner warning system. For mostly clear-weather, daytime ICW trips, a working fixed VHF with DSC, a proper lookout, and a charged handheld backup are a sensible starting point.
Just offshore, AIS can help you identify and track equipped ships, especially near shipping routes, at night, or in reduced visibility. A compatible display may show closest point of approach (CPA) and time to closest point of approach (TCPA), but those are projections based on reported data. They do not guarantee a collision warning or tell you what every nearby boat is doing. If you go beyond dependable VHF coverage, think about a properly registered EPIRB or PLB as part of your emergency plan; AIS does not replace one.
So should you buy a Class B AIS transceiver? Consider it if you often cross commercial traffic, run at night, or operate in reduced visibility and want your boat’s position broadcast to other AIS users. For occasional daytime coastal trips, it is reasonable to start with AIS reception—or no AIS—after confirming your VHF and DSC work. Broadcasting can make your boat visible on equipped ships’ displays, but it cannot guarantee anyone sees the target, gets an alarm, or maneuvers for you. Keep a lookout and follow the navigation rules either way. The IMO’s AIS guidance explains these limits in more detail.
Start with the equipment already on the boat
First check the fixed VHF. Does it transmit and receive on a proper radio check? Does it show a current GPS position? Is its MMSI registered with the correct boat information? Inspect the antenna and coax for damage or corrosion. A new radio connected to a failing antenna is not much of an upgrade. Do not use Channel 16 for a routine radio check.
Then check the chartplotter. Does it already show live AIS targets? If so, find out where that data comes from before buying another AIS receiver. On many newer boats, the chartplotter and other devices support NMEA 2000, but a compatible socket does not prove a backbone is installed or that the VHF is connected. Check the plotter’s network device list and the wiring behind the helm. A radio with its own GPS can supply its position for DSC without a chartplotter connection; the Standard Horizon GX2410GPS below can also show AIS targets on its own screen.
Add a handheld backup. It can be used away from the helm or if the boat’s electrical system fails. Keep it charged and somewhere you can reach it. Its small antenna generally limits its reach compared with a properly installed fixed VHF.
What if the VHF is flush mounted?
A radio set into the helm is still a fixed-mount VHF; “flush mount” describes the installation, not a separate class of radio. The Icom M330G and Standard Horizon GX2410GPS below can both be installed this way with the correct mounting kit. Some boats show only a handset at the helm because the main radio unit is mounted out of sight. Find that unit before deciding what needs replacing, and check its antenna, GPS source, MMSI, and voice and DSC setup. A handset alone does not tell you whether the boat has AIS.
If you are replacing a radio set into the dash, measure the existing opening and the space behind it before ordering. Then verify that the installed radio actually shows a valid GPS position. Standard Horizon cautions in its manual that the GX2410GPS’s front-panel GPS may need an external source when the radio is flush mounted. A clean-looking helm is no substitute for testing the system.
A quick buying flow for the boat in front of you
The chart below follows those checks, then asks whether you want to receive AIS targets and whether broadcasting your own position is worth the extra installation.
Fixed-mount VHF radios worth comparing
Icom M330G — a straightforward replacement. The Icom M330G at West Marine is compact, with 25-watt transmit power, Class D DSC, and a GPS receiver that uses an included external GPS puck. It fits a boat that needs a dependable primary VHF but already has AIS elsewhere—or does not need AIS. Check before buying: where the GPS puck and VHF antenna will go. This radio has no built-in AIS receiver.
Standard Horizon GX2410GPS — VHF with AIS reception. The GX2410GPS at West Marine combines DSC, built-in GPS, and an AIS receiver. If the radio has a current GPS position, it can show nearby AIS-equipped vessels on its own display without a connection to the chartplotter. When connected to compatible electronics, it can also share AIS data with them. It is a useful choice if the fixed VHF needs replacing and you want AIS traffic information. Check before buying: plotter compatibility if you want targets on the chartplotter. Its AIS receiver does not broadcast your boat’s position.
If the existing fixed VHF works well, you do not need to replace it merely to add AIS. A separate AIS receiver or transceiver may connect to a compatible chartplotter instead. Decide whether you want AIS before ordering a replacement radio so you do not buy twice.
Handheld VHF radios worth comparing
Standard Horizon HX210 — simple floating backup. The HX210 at West Marine floats and has a water-activated strobe. It makes sense when the fixed radio already handles DSC and you mainly want an independent voice radio. Know its limit: it has no built-in GPS, DSC distress calling, or AIS.
Standard Horizon HX891 — GPS and DSC in a handheld. The HX891 at West Marine floats and adds built-in GPS and DSC. Once its MMSI is properly programmed and it has a GPS fix, it can send a position-bearing DSC distress alert. Know its limit: it does not show AIS traffic. Keep its battery charged.
Icom M94D — handheld with AIS reception. The M94D at West Marine adds an AIS receiver to a floating handheld with GPS and DSC. It can show AIS targets away from the helm. Know its limits: AIS is receive-only, the small display is not a substitute for watching traffic, and it costs considerably more than a basic backup.
If you decide to broadcast AIS
A Class B installation is a separate decision from replacing the VHF. For example, the Garmin AIS 800 transceiver at West Marine receives AIS and broadcasts your boat’s information. It has GPS, a built-in VHF antenna splitter, and NMEA 2000/0183 connections for compatible displays. This is an example to compare if you have decided that transmitting makes sense for your trips, not a required purchase for every coastal boat. Confirm the plotter connection, antenna arrangement, MMSI programming, and installation cost before ordering.
The practical starting point
Make the fixed VHF, GPS/DSC setup, and antenna work first. Add a charged floating handheld. Check whether the plotter already receives AIS. Then decide whether seeing equipped traffic would help on your routes, and whether your boating habits justify broadcasting your own position. That order avoids replacing good equipment or paying for the same AIS function twice.
Our used-boat inspection guide covers the other electronics and safety gear to check before buying. The free one-page checklist is a quick reminder at a showing; the paid Used Boat Inspection Toolkit provides detailed worksheets for recording findings, comparing boats, and planning a purchase. Our essential boat safety gear guide can help you review the rest of the onboard setup.
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