The Echomaster is also what I use. There are two issues with it, though;
It is not a permanently mounted unit, and it won't work (no surprise here) when it is not hoisted up the mast. I often have to remind myself of this image I have of the bridge of the monster ship that is still a mile off, steaming at 25+ knots on a crossing course with us. The watch has his glazed eyes hypnotically fixed on the radar/AIS screen & never looks out at the small boat (us) in the path of the ship! Even on clear days, it is a good idea to hoist that thing. Ours goes to the second spreader. The higher the better, I think. It does clang around up there, so it is not practical to leave it up all the time.
It must be mounted in the catch rain position (as mentioned above) in order to reflect strongly. The mount for the one I have now is good for this. I had an older one on our first boat that did not have a way to mount it correctly.