I started pondering permanent installation of a signalling horn last night. I really am not quite sure I understand how a boat can be built without one from the factory but that is another story.
Here are the parts and pieces of my signalling horn I am installing in the Catalina. Yes, that is a compressor and an air tank you see...
I decided to go with a very yachty-sounding single trumpet horn from Kleinn Horns. The folks there were very helpful in discussing the options I had available to me.
What I think I want to do is install the compressor and air tank in the port hanging locker, next to the pressure pump for the water system. Depending on losses in the suply tubing, I may install the valve in there next to the tank, or I may put it up under the mast step. The horn is going to mount on the side of the mast and will be hard-plumbed to a fitting that exits the mast near the mast base. I will then use a piece of flexible braided stainless steel hose to go between the mast fitting and the deck fitting. This will keep all of the pressure line accessible for service, except the portion in the mast, probably 6 feet.
A few years ago my wife and I were out sailing the C22 in broad daylight and almost got run over by a powerboat that didn't see us, (How do you not see a sailboat???). this will make sure that anyone approaching sees us, after they HEAR us.