jfkal
Active member
Any ideas on what is the ideal height for a Radar attached to the mast (visibility vs weight aloft).
THX
THX
Radar Height
- Thread starter jfkal
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byron
RIP
The higher you can position the scanner the further the horizon becomes, ergo the further it can 'see'
Weight, entirely depends on a variety of factors but should not present a stability problem.
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Weight, entirely depends on a variety of factors but should not present a stability problem.
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brianhumber
New member
It is true the higher the scaner, the further the radar ( in theory) can see. But, plenty of yachts mount theirs on 3m poles at the stern and mine is below the lower crosstrees out of the genies way on the mast. If I was to use the 16 mile range it picks up vessels ok but in practice it only gets used on the lower ranges 6m or less
hlb
RIP
Mine gives plenty of range. Over 16 miles. So you dont need to go up very high. Never found a reason to look any further.
Dont forget to order your Burgee. PM me.
Haydn
Dont forget to order your Burgee. PM me.
Haydn
G
Guest
Guest
Look back at the replies I had when I asked a similar question on Sunday Feb 10.
LadyInBed
Well-known member
Weight is 3/5 of not a lot, so it doesn't matter.
As to hight, how long is the cable?
Standard cables are 10 or 15 mtrs, but you can get a 20 mtrs one.
So knock off the below deck cable run, say 4 mtrs, that means the head can be up to either 6 or 11 mtrs.
6 mtrs is more than adequate.
As to hight, how long is the cable?
Standard cables are 10 or 15 mtrs, but you can get a 20 mtrs one.
So knock off the below deck cable run, say 4 mtrs, that means the head can be up to either 6 or 11 mtrs.
6 mtrs is more than adequate.
Chris_Stannard
New member
Hate to disagree with people who say weight of the antenna is not important, it depends what you are fitting. Putting the antenna at the top of the mast will increase your roll inertia, and reduce the stiffness of the boat. The antenna also increases your windage. Obviously the size and weight of the antenna will be a factor in this. For example fitting a radar to a Sigma 362 redeced the angle of maximum stability by two degrees, not much but then you add all the modern things like roller reefing etc they can add up. Sensibly therefore I believe you have the antenna fairly low, mine is at the first cross trees about, 5 metres from the deck. This also reduces the chances of getting the sail all round it when tacking.
I get about 12 nm on merchant ships with the radar at this height. You can use the dip tables in the almanac to calculate when you should be able to see a merchant man remembering that you add the range for your antenna height, say 6 metres, to the range for his bridge height, say 10metres. You can then add about 10% for the fact that radar waves are refracted round the earth to a greater degree than light.
More important, if you are going to fit radar please go on a course to make sure you understand how to use it and the limitations it has, especially in high sea states. I would not be without mine.
Chris Stannard
I get about 12 nm on merchant ships with the radar at this height. You can use the dip tables in the almanac to calculate when you should be able to see a merchant man remembering that you add the range for your antenna height, say 6 metres, to the range for his bridge height, say 10metres. You can then add about 10% for the fact that radar waves are refracted round the earth to a greater degree than light.
More important, if you are going to fit radar please go on a course to make sure you understand how to use it and the limitations it has, especially in high sea states. I would not be without mine.
Chris Stannard
LadyInBed
Well-known member
Totally agree Chris, the point I was making, probably not very well, was it could not be put very high due to the length of cable supplied.
HaraldS
New member
Don't overdo the height.
Big ships you'll pick up because they are very high and who cares about small boats far away. Clouds and land of some elevation you will also always pick up. So the benefits are limited.
There are several down sides to radars mounted very high: Weight aloft and cable length have been mentioned, but another important aspect is that radar cannot see anything that is lower than the horizon, whether it is behind or in front. The radar cannot distinguish the signal reflected from the water, from anything on it.
If you climb up to your spreaders and look down at small boats and how far away they have to be to clearly come up higher than the horizon, you'll see what I mean.
Big ships you'll pick up because they are very high and who cares about small boats far away. Clouds and land of some elevation you will also always pick up. So the benefits are limited.
There are several down sides to radars mounted very high: Weight aloft and cable length have been mentioned, but another important aspect is that radar cannot see anything that is lower than the horizon, whether it is behind or in front. The radar cannot distinguish the signal reflected from the water, from anything on it.
If you climb up to your spreaders and look down at small boats and how far away they have to be to clearly come up higher than the horizon, you'll see what I mean.