How far will VHF radio transmit to Coast Guard from a swimmer in water

Most of the info I’ve seen assumes the operator is in a small boat, perhaps standing up. I’m more interested in how far I could transmit if I were swimming.

I’ve also been considering getting a PLB. I’m not so sure though. Part of my thinking was that if I were having some sort of medical emergency it might be easier to press a button than to talk on my VHF before I lose consciousness, or the dexterity to operate VHF (e.g., due to hypothermia), but after watching a video of someone using a PLB, I’m not so sure that it is substantially quicker or easier to use than a VHF. Perhaps.

Line of sight 3-8 miles 6 watt hand held. Depends on conditions and terrain. You can get a emergency atenna extender that extends you atenna height. Hooks into your radio and inflates. If you’re having something like a heart attack you’re probably not going to find it very useful. You’ll be laid out or as they say “be tits up” goes for all genders no offense meant.

You gain range by other boats hearing you call for help and relaying it.

This depends on mainly on the transmitting power of your radio and terrain, along with squelch, antenna and radio quality. Anything outside of line of sight is probably out. This means that trees or terrain obstructing yor line of sight will dramatically impact range. You will probably have slightly better range stiiting in a boat vs floating in the water. If you are in waves that are obstructing your view of the horizon this will impact range to vessels, probably not as much for aircraft though. If you are going to be doing something risky I would contact the manufacturer and get a realistic estimate for your conditions. I have used some incredibly expensive radios with 6’ whips and those would do 12 miles line of sight, and high quality but relatively inexpensive ones at a few miles line of sight without issue. I would get one that floats, is water resistant, preferably submersible, and has emergency position indicating radio Beacon. (EPIRB) if you can find it. You should also have a PFD that comfortably stores your radio. And if you’re planning on going for a swim and calling the Coast Guard, you should probably also have a flare gun in your PFD.

For an emergency; the best is a “SPOT” device - Next a PLB and last a VHF unless you need to do some talking
We use both a SPOT and a VHF, but every so often looking for a “radio check” you won’t get an answer unless some one is within range

Jack L

Line of sight formula to the horizon in nautical miles is 1.17 x square root of the height of the lighthouse. In your case assume your VHF is at water level and the height would be the height of the CG antenna. If their antenna is 10 feet high that’s 3.7 nm. Waves though can change that to almost zero - how long is your arm?

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Part of the answer relates to if the Coast Guard has repeater antennae up on high hills around. If they do, that will help.

We have areas here on the CA coast where no matter how strong your radio is, you won’t reach coast guard unless they happen to have a boat nearby. In these cases, the radio wont do you much good.

Keep in mind on the Spot or PLB, there is a delay in response. There could be a delay in connecting to the satellite, then a delay as the receiving office tries to determine what may be happening and who to call, and then the call is made.

I usually carry both PLB and VHF.

I haven’t made the jump yet, but if this is a concern, a radio with DSC might be part of your solution.

A good 5-6 watt VHF’s range is up to 5 miles over open water if you are in the kayak. In practical terms more often 2-3 miles to reach another kayaker or small boat. This is further reduced by being actually in the water or if land masses or other structures block line of site to the receiving station. Range is basically line of sight. The ability to obtain help can be greatly increased if there is a lot of large boat traffic around (in theory any boat that has a VHF is required to monitor VHF channel 16 at all times) or like around around the Chesapeake Bay the USCG has a extensive array of tall towers. A VHF is only to be used for marine use. It is not legal to use it like a walkie-talkie on land.

A DSC capable VHF radio typically has a single protected button, that when pushed will send out a constant distress signal with position. If properly registered the USCG will also have your name, type of boat, and contact information at a minimum. Once pushed you must contact the USCG or local 911 system by voice or VHF radio to cancel the distress call. Turning off the radio does not stop a response. Bear in mind, that unless there are other boats nearby, it can take the USCG an hour or more to get help on site. This goes for any distress signaling system.

Beyond this there are satellite based communication devices. These are generally able to be used anywhere in the world and do not normally have a range imitation as long as you have a clear view of the sky. All of these are required to be registered like VHF radios with DSC. Registration is usually free.

The most basic is the PLB or personal locator beacon. These can only send a distress signal and usually can not send messages or allow the cancelation of a distress signal once activated. This is not limited to maritime use. Some can send non-emergency location information.

Beyond this, and much more expensive are satellite messenger systems. In addition to the above devices, these allow sending of text messages, and in some cases receiving them You can generally cancel a distress signal. These require a subscription as well as registration, which can be fairly expensive. They can have, depending on how much you pay, a wide range of other abilities. These might include advanced GPS abilities, two way text or voice communication, non-emergency two way communication and location information, other radio bands including VHF, strobe light, etc.

In addition to the above is the EPIRB (emergency position-indicating radio beacons. Unlike the devices above, an EPIRB is registered to a vessel rather than a person and is only for maritime use. These are pretty limited in function but a fairly expensive due to USCG requirements they must meet. They generally come with a strobe mounted on top and must be waterproof and float upright. They are generally more powerful that the devices above and must be able to transmit for a minimum of 48 hours continuously. Some are designed to begin transmitting automatically when in the water and released automatically if a boat sinks. There is a long list of technical specifications these must meet to be certified. They tend to be heavy, bulky and very expensive compared to other emergency distress signaling devices. They are not really suitable for a kayak.

Some people, in addition to a VHF, carry a PLB if they are in remotes areas or inland areas with no USCG coverage.

rstevens15, as always you are a wealth of information. I have a VHF radio question for you or anyone really. When I am on the water with my wife and if we both have VHF radios are we permitted to go to a clear channel to communicate with each other when we are out of ear shot on the water?

Yes, indeed. That’s what most kayakers use a VHF radio for. It is invaluable for keeping a group together if it gets strung out if both the lead and sweep have radios. On some of our more advanced trips, some of our volunteer leaders now require VHF radios for everyone. Otherwise, if people have them, we encourage people to bring them. The prices have come down dramatically for a decent radio.

Whenever we go out we always pick a channel and do a radio check when starting out. Channel 16 is a hailing and distress channel. If you have not picked a channel beforehand, you use this to contact someone, as in theory everyone with a VHF should monitor channel 16 at all times. However, I’ve never heard of anyone being sent to Guantanamo for not doing this. In busy areas, channel 16 can be pretty busy and annoying. Once you have contacted someone, you should pick a “working channel” and both switch to it. Do not use channel 16 for conversation. It is monitored by the USCG at all times for distress calls. The USCG also used channel 22α as a secondary channel for handling distress calls to free up 16.

Working channels are 68, 69, 71, 72, and 78. The USCG recommends channel 9 for radio checks, but in my experience, only the USCG and commercial vessels monitor these channels on a regular basis and usually do not respond to recreational boaters’ radio checks. If you’ve agreed to a channel you will be using, use that. The USCG tends to get pissed off at people using channel 16 for radio checks.

The USCG is experimenting with an automated radio check channel in some areas, although my experience has been it does not work that well for 5-6 watt handheld radios unless you are very close to the tower. These towers are only in certain areas and use different channels. Handheld radios are limited at this time to 6 watts. Fixed radios in powerboats are usually 25 watts and have much better range and high external antennas.

Most VHF radios these days also come with the NOAA weather channels and have a weather alert mode for severe weather. Invaluable on the water, especially in the summer with pop up thunderstorms around where I am. Most can also scan more than on channel. I often scan our chosen channel, 16, and the appropriate weather channel.

Thank you!
Any good recommendations for a decent pair of radio’s for use in our area? I recognize you, I recently joined CPA.

I’ll have to leave it to others for current recommendations. I’ve always likes the radios by Standard Horizon.

My wife has an HX500S and I have a newer HX870 with the DSC feature. She’s had hers for over 10 years and I’ve had mine for over 5. Both are now superseded by newer models. Before that I had a an HX280 for about 15 years that still worked great with the original battery until someone dropped it overboard.

I chose the 870 with the DSC feature because I have done a lot of long distance solo paddling on open water and in isolated areas and felt the distress feature was a good idea. The feature causes the radio to cost significantly more and many people might not see a need for this feature. It also incorporates a full featured GPS, but I generally always carry a separate GPS as it’s easier to use and increases battery life for the radio. The 870 has been superseded by the 890. The HX 890 adds a number of features such as an FM radio, the ability to use a scrambled communications option, and can supposedly provide the position information of up to nine other selected vessels with DSC capability.

So I am not that up on the latest radios. They seem to come up with updated model all the time while the price stays the same or even drops.

A lot of people seem to like the radios by Icom as well. Uniden makes West Marine radios, but i haven’t heard much about them. West Marine sell all three brands and runs frequent sales.

Many surveys seem to pick the Standard Horizon radios as the top pick. Very good warranty as well. Last I knew 3 years including for water damage and after that a lifetime flat rate replacement fee for the original owner.

Yeah your antenna hight matters a ton, thats why all off shore boats run there whips as high as possible. Waves definitely obstruct you’re line of sight, and listed ranges are just advertising for ideal conditions. If you were swinnming as sugested by the OP, I would assume this is because you swamped. I feel like in this senario a hand held is only going to help coodinate the rescue once the CG has located you. It’s probably not going to be very useful at all in helping the CG locate you.

With DSC capability, a GPS position signal is continuously broadcast if the distress function is activated… For the Standard Horizon HX 870 it also has a full featured GPS so you can radio your position as well. On the Chesapeake with its arrays of tall USCG towers, even a swimmer in the water will probably get a signal out. Other boats with DSC will also receive your position and the USCG will broadcast your position and boat type over channel 16.

Offshore beyond the radio’s range and no other boats in range, it will be a different story. For that you need a PLB or other satellite communication device of some type. Some people carry both if paddling in those sorts of places.

If you look at the USCG Rescue 21 coverage areas you can get an idea how well the CG can receive VHF in a given area. The minimum standard is that a CG antenna should receive a one watt transmission with an antenna six feet off the water (yes that applies to boats, not swimmers) for a range of twenty miles. The maps, depending where you are may have significant overlap and well exceed the twenty mile minimum. At least on the US East coast, the coverage is blanketed. So a six watt VHF voice or DSC transmission at sea level still has a very good chance of getting to the CG. A VHF isn’t a substitute for a PLB but can be a suitable addition.

Line of sight for a VHF antenna about 2’ off the water and a 100’ CG tower would be about 16 miles. Even if you’re floating in the water, the Rescue 21 standard would likely be met.

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