The radar lobe are usually ±15° vertically. That means that it goes 15° below the horizon. If you mount the dome on a pole in the aft of the boat 2.7 m above the waterline, the lobe comes down to the waterline 10 m forward of the pole. (10 m x tan(15°) = 2.7 m). On a 13.8 m boat it means that the front cabin
is in the field.
The power in the signal of a broadband
radar is a factor 10000 lower than on a pulse radar. That’s so low that either the SART or RACON will be activated. But since energy is power multiplied by time, and the broadband
radar transmits continuously while the pulse radar transmits with very short pulses, the energy in the signal I “only” a factor 10 lower. If you believe that the field from a radar ain’t healthy, then is the broadband radar not a solution.
I have seen many boats that have mounted the dome on a pole in exact the same height as the boom. When they sail with wind
from astern and have the boom out across I believe that the boom can interfere with the radar considerably.
Once I was sailing over the Atlantic and we have hade a lot of wind
for some time so the waves hade come up in height a little. When I was standing in the cockpit
with my eyes about 2.5 m above the waterline I saw nothing of the boat that we sailed along with even though they had a 20 m high mast
. It dose not mean that the waves was 20 m high but more that my low eye level limit the visibility considerably.
I have a 0.45 m dome that have a weight of 5 kg. Either if you mount on a pole or on the mast, it need to be a quite strong place. If it’s mounted in the mast, a natural strong place I where there are spreaders. Since you don’t wont to have too much weight high up in the mast, the lowest spreader pair is suitable.
In my home harbour we take of the mast when wee take up the boot for the winter and I have problem whit the dome cable every year. Furuno have a stand-alone system where the dome only has a power cable and the signal goes via wifi
to the ipad
that works as display.