radar ; arch or mast?

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Half Moon

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I am soon to become an owner of a sailing cat with radar. The dome unit is now on the arch over the aft of the cockpit. I am wondering if it would be better to place the unit on the mast above the fore stay on the fractional rig. To my thinking the benefit would be a clear pattern forward at a significant altitude that would enhance both range and clarity. It would also keep the microwaves from cooking my aging brain as the arch is in back of the steering station. The two negatives would be weight aloft and the expense to run cable up the mast for the relocation. I have never used radar before. I have seen the dome mounted on separate dedicated mini masts aft, on arches over the cockpit and high up on the main mast. Any experience with dome placements??
 
Putting the radar up the mast will increase the range but it reduces small close target aquisition. There isnt enough microwave energy to fry your brain.

Mounted on an arch the radar will give returns from small objects such as fishing floats and will not be affected by clutter. Yes its range will be compromised but are you that interested in targets over 10 miles away?
 
Dont forget the effect on your boats stability. The bit of the mast you are referring to will be the top 25% or even less. Your AVS on a cat is likely to be 45 deg or less. Waves can easily take up 15 deg of that so you dont really want to reduce the remaining 25 / 30 deg by having a weight near the top of the mast.

In any case, why add to the list of jobs that really need doing?
 
A further aspect to consider is the relative angle of movement due to pitching and yawing. Reduced on a cat, but still signficant.
I put my radar on a tower 2.5m above deck on the transom rail.
 
If I where to fit a radar again it would be on a pole at the back rather than up the mast as I have done;

Easier to take the mast down,
Accessible if the connecting plug develops some corrossion after not being used over the winter,
and when I do use it I rarely have the range over 8 miles.

But not a radar expert at all and have a heavyish keel boat..
 
Marsupial said:
Putting the radar up the mast will increase the range but it reduces small close target aquisition. There isnt enough microwave energy to fry your brain.
.....
?
Click to expand...

Safe microwave levels are quoted in milliwatts.
Radar power is quoted in kilowatts.


ymmv!
 
I saw two guys fit a radar on the cat in the berth opposite me.

They mounted it on the mast at the height of their ladder, which they used to climb up and fit...It made a lot of sense, tho not something I'd recommend on the monohul on the water! :)

I fitted mine on a scanstrut pole at the back of my monohul, easy to fit, could almost do it single handed, it's easy to remove the radar if I need to...Simple instructions, only downside is the cost....but by the time you've spent time hunting around for all the bits to make you're own it's works out about the same.
 
FullCircle said:
Guide to Radar safe distances here.

http://www.panbo.com/Pulse_Radar_Safety_courtesy_Navico.pdf


in general terms, Occupational safe distance for 4Kw is max 0.8m
Click to expand...

If you follow the references in that link, there are some intersting studies regarding the effects of the lower frequencies and power levels of mobile phones.

It also states that 'occupatonal' limits are not appropriate in the leisure market, 'general public' limits should be used.

It's quite amazing how little work has been done or published on the effects of pulsed RF, but there is some evidence that it has effects on the brain (or at least evidence that we need better studies...). Some studies show improved memory.
From skimming a few papers on the subject, it seems that where there is evidence of effects, it tends to be where the pulse repetition freq is close to the speed that processes in the brain work, a bit like some frequencies of strobe lights can have effects on some people.

Perhaps this explains some of the decisions that have been made in 'Radar Assisted Collisions'?

I work with RF and if I could afford a boat with a radar, I would not be sitting in the beam.
It's probably perfectly safe for 'other people' like that Tory minister and his BSE burgers...
 
lw395 said:
If you follow the references in that link, there are some intersting studies regarding the effects of the lower frequencies and power levels of mobile phones.

It also states that 'occupatonal' limits are not appropriate in the leisure market, 'general public' limits should be used.

It's quite amazing how little work has been done or published on the effects of pulsed RF, but there is some evidence that it has effects on the brain (or at least evidence that we need better studies...). Some studies show improved memory.
From skimming a few papers on the subject, it seems that where there is evidence of effects, it tends to be where the pulse repetition freq is close to the speed that processes in the brain work, a bit like some frequencies of strobe lights can have effects on some people.

Perhaps this explains some of the decisions that have been made in 'Radar Assisted Collisions'?

I work with RF and if I could afford a boat with a radar, I would not be sitting in the beam.
It's probably perfectly safe for 'other people' like that Tory minister and his BSE burgers...
Click to expand...


I did follow the links - very interesting indeed.

My Tower was set at 2.5m above deck so that the beam would pass harmlessly overhead, assuming no reflection.
I also work on big ship radar, and have talked to my colleagues....

History has not recorded what happened to Miss Selwyn-Gummer.
 
Half Moon said:
I am soon to become an owner of a sailing cat with radar. The dome unit is now on the arch over the aft of the cockpit. I am wondering if it would be better to place the unit on the mast above the fore stay on the fractional rig. To my thinking the benefit would be a clear pattern forward at a significant altitude that would enhance both range and clarity. It would also keep the microwaves from cooking my aging brain as the arch is in back of the steering station. The two negatives would be weight aloft and the expense to run cable up the mast for the relocation. I have never used radar before. I have seen the dome mounted on separate dedicated mini masts aft, on arches over the cockpit and high up on the main mast. Any experience with dome placements??
Click to expand...

I would without doubt leave it where it is.

Ask your self:

1 Do you need 20 miles range
OR
2. Do you really want good clarity at 6 miles

Mounting high up increases the sea clutter VERY BADLY, making 1 to 6 miles definition in bad weather difficult, as you have to reduce sea clutter - you therefore won't see smaller objects.

Leave it and have one job less!
 
FullCircle said:
I did follow the links - very interesting indeed.

My Tower was set at 2.5m above deck so that the beam would pass harmlessly overhead, assuming no reflection.
I also work on big ship radar, and have talked to my colleagues....

History has not recorded what happened to Miss Selwyn-Gummer.
Click to expand...

2.5m is a lot higher than some.
I have a feeling that there is probably a lot of unpublished (read Military) research on this subject.
As well as those urban myths (?) about 'real' radar engineers only having female children....


I expect Ms hyphen-Gummer got married asap just to change her surname?

Cheers,
 
Compromise?

I bought a new plotter last year, and it came with a radar which I have yet to fit to my Sun Odyssey 32. I have been pondering the best location for the radar, and concluded that the mast is the best place, but have not decided how far up. I am now considering putting it well below the spreaders so that I can fit it using a small extension ladder, say 10 foot above deck level. I've never seen a radar dome this low on a single masted monohull - is there something obviously wrong with doing this (other than it might look funny. The genoa does have an overlap but it isn't huge.
 
DeepJoy said:
I bought a new plotter last year, and it came with a radar which I have yet to fit to my Sun Odyssey 32. I have been pondering the best location for the radar, and concluded that the mast is the best place, but have not decided how far up. I am now considering putting it well below the spreaders so that I can fit it using a small extension ladder, say 10 foot above deck level. I've never seen a radar dome this low on a single masted monohull - is there something obviously wrong with doing this (other than it might look funny. The genoa does have an overlap but it isn't huge.
Click to expand...

I ve had lots of boats with radar up the mast and on poles, IMHO and experience, the best place for it is on a pole or arch with the monitor close to the helm.
 
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