Unity gain antenna?

My back-up VHF radio is a portable. I also use it to monitor channel 13 (busy in SE Alaska), as I don't like to have my main radio scanning (you miss a lot). I have it mounted in its charger at the helm. I like this arrangement, except that reception is poor. I am considering an external antenna, but I want a small size antenna (less that 12") as I already have 2 larger antennas mounted (VHF and AIS). A third antenna would get in the way or kayaks on the roof. I am not interested in splitters.

My question: Is it worth going to a small unity gain antenna like this one:

https://defender.com/en_us/scout-km-10-vhf-fiberglass-antenna-7-18-cm

or would benefit be marginal? Even though the cabin of our C-22 is fiberglass, I think the aluminum window frames are causing problems. Thanks for your thoughts.

The antenna you cited will be unity. There are a number of antennas which are 3 db gain. There are Marine VHF 36" (1/2 wave) base loaded antennas, by Metz, Shakespheare, and Conrad (others--but these are the main ones--for the most part they have very thin and flexible (spring back to place) 36" wires as the radiator/reciever element. There are also 3 db gain antennas which are fitted to be used on a hand held. It will depend on the type of fitting which the base connects to--but Powerworx has several which fit on ham 2 meter which have a range from 140 to 170 mhz, which will cover the Marine vhf bands and 3 db grain. This should give better reception and transmission on your hand held than it's standard antenna, but will still be lower than one mounted on the roof of the C Dory--in a port or traffic situation, the height will not matter as much as for long distances. I have used both of these types for Marine VHF.

Thanks Bob! I should clarify: I am willing to put the antenna on the roof, probably on my roof rack, but I am hoping to get away with a short antenna that will make it easy to lift a kayak over. I've already boxed the kayaks in with two 36" antennas, so I am trying to avoid a third 36" antenna. The other two antennas are Morad and Gam--very happy with both. Also, thanks for mentioning Powerwerx--I have several of their radios and antennas and I am very happy with the products and support they offer.