I put a B&G 4G radar unit on Jerezana four years ago. It looks large on my small boat but it is actually a fairly compact dome. I used an Edson mast mount.
http://www.bandg.com/en-US/Products/Broadband-4G-Radar/
http://www.defender.com/product.jsp?pat ... id=1583200
Complete overkill for my boat and, except for curiosity, I haven't needed to use it. But at the time my Pa offered to get me a radar which, in his mind, was an essential piece of gear - but his active sailing days ended before wide spread use of GPS.
4G radar is the Simrad/Lowrance/B&G term for FMCW radar (frequency modulated constant wave) radar which is quite different from pulse radar. They also call it "Broadband" You can Google all the terms. There are several things to know about this type of radar. Number one - it has less radiation risk than your cell phone, and way less than pulse radar - so you can mount the dome on the flying bridge of a center console stink pot, for instance, and be unworried about exposure. And it uses very little power for a radar - I think 10 watts. Generally speaking it has less range than trad pulse designs. B&G claims 36 miles - I've never seen more than 20 on mine, but mine is mounted quite low. On the other hand this radome can see right up close really well basically because there is no pulse gap (ie speed of light "blind" interval of the pulse). My unit for instance easily showed the slips and boats when I was birthed at Shipyard Marina in Boston Harbor, even the boats next to me. It sees all the boats at their moorings in Marion. I think of it as a very good short range radar. For that reason, and for physically clearing my various jibs, and to decrease weight aloft I mounted the dome fairly low.
My thinking was that since the advent of GPS, radar (for me) would be most useful for seeing boat traffic in fog or at night at fairly close distances (never more than 10 miles - typically a mile or two), so I went with this unit. My Dad used radar to snoop into fog bound harbors in his day. We just don't need that technique with GPS anymore. It also helped that it integrates with my B&G Touch plotter via a proprietary NEMA 2000 data cable set, and can overlay on the chart displayed on the plotter - or be viewed discreetly on the plotter as well. The reason this is so useful is because the underlying map helps you id blips that are not bouys or rocks or other objects. If you see a blip where there is nothing on the chart, well, it's probably a boat.
I would completely differ to other more experienced sailors about more traditional radar. I know (only from reading) that one important use can be tracking squall lines, and there I think the more standard pulse units high on a mast would be the thing you'd want.
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