Should you buy a handheld or a fixed-mount marine VHF?

The question almost always arrives as a power question. Six watts or twenty-five? It’s close to the least interesting number in the decision.

VHF is a line-of-sight service. What decides how far you get heard is mostly how high the antenna sits and what it can see from there — which is why a fixed set feeding a masthead whip reaches boats a handheld at chest height never will, and why the same handheld does noticeably better held up on a flybridge than down in a cockpit.

Does a fixed-mount VHF really outrange a handheld?

Yes, and the antenna is doing most of that work rather than the extra watts. The BoatUS Foundation states it plainly: VHF signals travel by line of sight, “therefore the higher the antenna, the farther your signal will reach over the horizon,” and “in general, the higher the antenna, the better the range of your radio.” Its own radio testing sets the general expectation as a range “of up to 20 miles, depending on the height of the antenna and its ‘gain’”. Notice what is absent from that sentence: transmit power.

The US Coast Guard Navigation Center frames the same expectation from the other end — “Your VHF radio is intended mainly for short range communications, generally 5-10 miles, and at least 20 miles to a USCG station.” That last clause is the tell. A shore station wins its extra reach with a tall antenna and a good receiver, not by shouting.

If you want the geometry: distance to the radio horizon grows with the square root of antenna height, so doubling an antenna’s height buys roughly 1.4 times the horizon, while multiplying power buys almost nothing once the far station has dropped below the curve. That’s arithmetic, not a manufacturer figure.

How much transmit power are you actually allowed to use?

Under US federal law a marine VHF ship station may not exceed 25 watts, and it has to be able to drop to one watt or less. The FCC puts it in one line: “The power output of your ship station radio must not be more than 25 watts when operating in the 156-162 MHz band,” and “You must also be able to lower the power of your radio to one watt or less.”

The rule text carries a detail most buying advice skips. 47 CFR 80.215(g) requires that the carrier power of ship station radiotelephone transmitters, “except portable transmitters,” in the 156-162 MHz band “must be at least 8 but not more than 25 watts.” So 25 watts is a ceiling, and for anything that isn’t a portable there’s also a floor of 8 watts. Handhelds are carved out of that floor, which is exactly how a fully legal marine VHF ships with a 6-watt maximum.

The same section explains the 1-watt tier on the channel selector. Every transmitter “must be capable of reducing the carrier power to one watt or less,” and sets made after January 21, 1987 or in use after January 21, 1997 must reduce automatically on 156.375 MHz and 156.650 MHz — channels 67 and 13. Paragraph (g)(4) exempts hand-held portables from that automatic step. Low power is a courtesy setting for close-quarters traffic, not a lesser radio.

Why is a handheld still the right second radio?

Because it carries its own power and it leaves the boat with you. A fixed-mount set is, in Uniden’s own description, “wired into the boat and paired with an external antenna”. That arrangement is what gives it range, and it’s also what ties it to the boat’s battery bank, its coax run and its deck fittings.

Every one of those is a single point of failure the handheld does not share. A flooded engine space, a chafed antenna cable, a switched-off isolator, or the decision to get into a liferaft all take the fixed set out of service and leave the handheld working. That’s the case for owning both, and it isn’t the same as “the handheld is the cheaper radio.” It’s the radio for the moment the boat stops being the thing you communicate from.

Do the waterproof ratings on marine radios actually differ?

Yes, but not in the direction the numbers suggest — IPX7 and IPX8 are different claims, not two rungs of one ladder. IPX7 is a fixed test: Icom states its IC-M94D is “IPX7 submersible (1 m depth of water for 30 minutes)”. IPX8 has no fixed depth in the standard — the manufacturer sets it, which is why Uniden’s Atlantis 275 is “IPX8† (submersible to 4.9 feet for 30 minutes)” while Standard Horizon’s HX891BT/E is waterproof “to the IPX-8 standard which is 1.5m for 30 minutes”. Our IP rating guide works through why that’s the standard behaving as designed rather than a loophole.

The clearest illustration sits inside one maker’s range. Icom rates the fixed-mount IC-M510 to “IP68 advanced waterproofing (1 m depth of water for 60 minutes)” — a shallower depth than Uniden’s IPX8 handheld, for twice as long. Neither number is “better”; they answer different questions.

Floating is a third thing again, and no IP code implies it. Icom’s IC-M25 is IPX7 and floats; Cobra’s MR HH600 advertises a “floating design and orange core” and publishes no IP code on its product page at all. For a radio that spends its life clipped to a lifejacket, floating is the specification that matters most, and it has to be claimed separately.

What do the manufacturers actually publish?

Not the same things — and several of these makers don’t publish the figure at all.

Radio	Type	Published TX power	IP rating	Floats?	Internal GPS / DSC
Standard Horizon HX891BT/E	Handheld	6 / 2 / 1 W	IPX8, 1.5 m for 30 min	Yes, floats face up	66-channel GPS; DSC Class H
Icom IC-M94D	Handheld	6 W / 1 W	IPX7, 1 m for 30 min	Yes	GPS; DSC Class H; AIS receiver
Icom IC-M25	Handheld	5 W (approx.) / 1 W	IPX7, 1 m for 30 min	Yes	Not published
Uniden Atlantis 275	Handheld	6 W	IPX8, 4.9 ft for 30 min	Yes	Not published
Cobra MR HH600	Handheld	6 / 3 / 1 W	Not published	Yes	GPS; DSC (class not published)
Standard Horizon GX1400GPS/E	Fixed	25 W / 1 W	IPX8, 1.5 m for 30 min	n/a	66-channel GPS; DSC Class D
Icom IC-M510	Fixed	25 W / 1 W	IP68, 1 m for 60 min	n/a	GNSS receiver; DSC Class D
Uniden UM725	Fixed	25 W / 1 W	IPX8, 4.9 ft for 30 min	n/a	GPS on some variants; DSC send and receive
Cobra MR F77W GPS	Fixed	Not published	IPX8 (JIS8)	n/a	GPS; “DSC-capable,” class not published

The two Standard Horizon pages are the European listings, whose model numbers carry an /E suffix; US variants drop it. “Not published” means the maker’s own product page doesn’t state the figure. We did not fill those cells from a retailer.

Does a handheld’s DSC work as well as a fixed set’s?

Only if the handheld has its own GPS and its own programmed MMSI — a distress button is worth what those two things are worth. Uniden’s explainer is the clearest short statement of the dependency: DSC “allows a compatible radio to send a formatted digital distress alert,” and “when the radio has been programmed with a Maritime Mobile Service Identity number and connected to a working GPS source, the alert can include the vessel’s identity and position.”

That dependency lands differently on the two radio types. A fixed set can take position from the boat’s network, and it usually has an MMSI because the boat does. A handheld is most likely to be used at the moment it is no longer on that network, so it needs a GPS receiver inside it — which is exactly the line between the IC-M94D and HX891BT/E and the IC-M25 and Atlantis 275, which publish neither. The second pair are decent radios for a tender; they aren’t distress-alerting devices. Read the class designations off the table too: Standard Horizon and Icom both label their handhelds Class H and their fixed sets Class D. Our guide to VHF DSC and MMSI covers how the number is issued and what happens when a boat changes hands.

Does it matter that the fixed set talks to the rest of the boat?

It matters more than the wattage does, because a fixed set is the one radio wired into the boat’s data network. Position and AIS data move over NMEA 2000 between the radio and the chartplotter, which is where Garmin, Raymarine and Furuno sit in most installations. Icom’s IC-M94D shows how far that has come down-market: it publishes an integrated AIS receiver, so vessel traffic appears on a radio you hold in one hand. Our AIS guide covers what those targets are and are not.

The short version

Buy the fixed-mount first and spend the money on the antenna and its mounting height, because line of sight sets range and 25 watts into a low antenna isn’t a fix for that. Under US federal law 25 watts is the ceiling, one watt or less is a required setting, and 8 watts is a floor that exempts portables — which is why handhelds top out around 6 watts, and why that isn’t the failure people take it for. Then add a handheld, chosen for whether it floats and whether it carries its own GPS and MMSI, because its job starts when the boat’s power, antenna or hull stops being available. Read the waterproof claim rather than the digit.