VHF 2.5 vs 5 watts

Would there be much difference in range between a 2.5 watt VHF radio and a 5 watt radio when transmitting from the height of a kayak or even while in the water (in a worst-case scenario where the kayak has drifted off)?

I know VHFs are limited by line of sight so I was thinking maybe the very low height above the water would be more limiting than the power.

even a 60 watt radio
at kayak height will only transmit 5 nautical miles.

It probably depends on where you kayak.For me witn no traffic in the places I paddle, I want the capability of more power.

Not that I have to use it. I have a M24 by Icomm… basic but it has dual power levels.

Also consider if you need help and say you get a boat that’s say 5 miles away and they relay to Coast Guard which now sends a chopper. Its way up in the air so line of sight will be much longer than 5 miles now.They use your radio signal to home in on you. So you want as much power as possible.

Good question!
Roughly a factor of 1.4

Transmit power makes a difference for VHF range from the seat of a kayak. At a distance of about 5 miles, I’ve been unable to reach a ~50 foot tall land station (obscurred by islands) using Medium power (2 or 3 watts I think), but had a perfectly clear conversation moments later using High power (6 watts).

It’s true that range is limited somewhat by our height in a kayak, but you’re not always trying to reach another boat with an antenna close to the water. The Coast Guard maintains very tall antennas all along the coast, and when you’re trying to reach a receiver that’s 500 feet high, it doesn’t really matter whether your antenna is 2 feet or 20 feet off the water. The strength of your transmitter matters more in this case, where you need the power to push your signal to that very tall, but perhaps distant, USCG receiver.

In my area, coverage for the wide area beyond Schoodic Peninsula through Penobscot Bay is provided by a tower on Swans Island. That tower could be 30 miles from me, but line of sight generally isn’t an issue because of height.


In short, I’d recommend buying a VHF with 5 or 6 watt power, and all the leading brands I’ve seen are sold that way.

thanks, that was good
Relatable experiences are helpful.

Its a little complicated
Technically, VHF communication is not limited to line of sight situations. However, using a handheld radio with little power and the poor antenna they come with means your signal will likely be blocked by landmasses and reliable communication with another handheld radio will likely be limited to a few miles at best.

A general rule is that to make a meaningful difference in a received signal requires doubling of power, but when using FM it gets more complicated. Squelch thresholds will play a big role.

So in theory the difference between 2.5W and 5W is minor, but in practice it often is not as Nate related.

How far you can reach with a handheld VHF radio is really determined by the radio, squelch setting and antenna at the receiving end. You might easily be able to communicate well over 15 miles under the right circumstances even if you do not have line of sight signal path. With line of sight signal path 2.5W will work for over 50 miles if there is a good receiver and antenna at the other end.

had clear communication with the coast guard at 14 miles before and went thru or over or however …several Islands…not line of site. Hand held at 5 Watts. sometimes it must bounce off a cloud:}

Best Wishes