Why would you want to intentionally represent you boat as something it isn't? Not just a boat of a different size, but a railroad engine? The first cue a horn signal gives you is to then look for some kind of visual confirmation, by eyes or by radar; with either, you then look and listen for something that matches, with as little confusion as possible. If I'm headed up the Hudson River, or towards a railroad lift bridge, or up the Carquinez Strait for that matter, I really want to know what's a train and what's not, without a moment of further confusion. Or I hear a horn that should belong to a big ship, or a low whistle that should belong to a land based fog horn, but can't find one. It may sound pedantic to all you weekend warriors out there, but it's no laughing matter when you are in a position of trying to sort out all sorts of conflicting input, particularly in a crowded and/or confined area.
We use the horns a lot for all their prescribed uses. On the Hatteras the compressor was OEM engine mount. For you guys who don't have occasion to do so, exercise them regularly. And carry a portable back up for last ditch use. The last thing you want is for it not to work when you do need it to work.
"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"