You may have noticed that many of these have a booster which requires 12v supply. So that's good isn't it that the manufacturer boosts the signal? well not really, it needs a booster because the antenna
is rubbish to start with and the 12v supply to the booster just another thing you can do without on a yacht.
Instead why not use a yagi aerial, which is directional, doesn't need a booster and therefore doesn't need 12v etc. It is flexible enough to generally work
but a shift in tides might cause a problem and need redirecting.
Ours looks like this and cost £5 from e bay. Its mounted on the spinnaker
track on the mast
just above head
height. It gives a really good picture without the need for boosters etc.
One other point, the UK switched to digital signals about 4 years ago. Once the aerial needed to be horizontal, now they need to be vertical which most folk don't realise so go and buy a booster rather than just turn the aerial on its side for the best reception