Pole mounted radar - issues?

[robmcg]

I was wondering what the collective wisdom is regarding mounting a radar scanner on a pole at the aft end of a yacht. I appreciate range will be reduced compared to mast mounting, but by how much in real terms? Are there any specific perceived negatives with this arrangement and are there any forum members willing to share photos of their pole mounted radar domes?

Rob

 

[knuterikt]

I was wondering what the collective wisdom is regarding mounting a radar scanner on a pole at the aft end of a yacht. I appreciate range will be reduced compared to mast mounting, but by how much in real terms? Are there any specific perceived negatives with this arrangement and are there any forum members willing to share photos of their pole mounted radar domes?

Rob

Here is a link to a Radar Horizon calculator http://www.furunousa.com/LearningCenter/Radar-Horizon-Calculator.aspx

Where to mount the radar will always be a compromise.
The higher you mount
-The more movement you get
-The longer distance you can "see"

Mounting on a pole have some advantages.
-Easier to pull cables
-Less weight aloft
-No interfering with sails.
-Blind spot from mast is reduced

The best picture I could find now

This one also doubles as a crane to lift the outboard.

 

[aluijten]

I was wondering what the collective wisdom is regarding mounting a radar scanner on a pole at the aft end of a yacht. I appreciate range will be reduced compared to mast mounting, but by how much in real terms? Are there any specific perceived negatives with this arrangement and are there any forum members willing to share photos of their pole mounted radar domes?

Rob

I've done this last year. The drawback of the lower height is that you really need to consider a gimballed dome carrier if you have a monohull that will heel quickly.
For example the radarbeam for the standard Raymarine domes has a +/- 12.5 degree opening (so a total of 25 degrees) in the vertical plane. This means as soon as you go over this angle the sight of the radar is limited in the port and starboard directions. So at leas you should consider if this is a problem in your specific situation.
The advantage is that you don't need to fiddle with the radar cable when unstepping the mast. Nor do you have issues with the foresail when tacking.
For me the first advantage was important as out boat goes inside every winter, requiring the removal of the mast. Also we have a cutter rig, making the placement even more complex.

Cheers,

Arno

 

[pvb]

The drawback of the lower height is that you really need to consider a gimballed dome carrier if you have a monohull that will heel quickly.
For example the radarbeam for the standard Raymarine domes has a +/- 12.5 degree opening (so a total of 25 degrees) in the vertical plane. This means as soon as you go over this angle the sight of the radar is limited in the port and starboard directions. So at leas you should consider if this is a problem in your specific situation.

Surely the same observation applies to mast-mounted ungimballed radomes?

 

[pvb]

I was wondering what the collective wisdom is regarding mounting a radar scanner on a pole at the aft end of a yacht. I appreciate range will be reduced compared to mast mounting, but by how much in real terms? Are there any specific perceived negatives with this arrangement and are there any forum members willing to share photos of their pole mounted radar domes?

Range is marginally reduced, but ships should still be visible at 10-12 miles, which is plenty for most people. The lower scanner results in reduced sea clutter. The mast shadow is obviously much less. Wiring is easy. Depending on the pole, it can be easy to lower the radome to deck level for servicing (the Scanstrut pole I used has a ball-joint at the base). Weight aloft is marginally reduced. The pole is handy for mounting other antennae, or a small crane, cockpit floodlight, etc. Some people think that there's a health risk from radiation to crew standing on the deck - in practice, the emissions are so tiny the risk is probably less than continued exposure to mobile phones. Here's a pic of mine...

 

[prv]

Some people think that there's a health risk from radiation to crew standing on the deck - in practice, the emissions are so tiny the risk is probably less than continued exposure to mobile phones.

"Some people" includes Raymarine, who state that the eyes are especially vulnerable. A typical scanner is either 2 or 4 kilowatts - ok, you're not going to cop all of that unless you bear-hug the radome, but the closer you stand to it the more you will absorb (because you subtend a greater angle).

I wouldn't worry too much about being in the beam on the foredeck, but I would want the scanner above standing-on-the-seats head height at the cockpit.

Pete

 

[aluijten]

Surely the same observation applies to mast-mounted ungimballed radomes?

It does but because of a higher position to a lesser extent.

 

[pvb]

"Some people" includes Raymarine, who state that the eyes are especially vulnerable. A typical scanner is either 2 or 4 kilowatts - ok, you're not going to cop all of that unless you bear-hug the radome, but the closer you stand to it the more you will absorb (because you subtend a greater angle).

But Raymarine also say "the energy absorbed from an ordinary mobile phone can be several times greater than that from a correctly installed Raymarine radar." And there have been many reports which underline the inherently low risk of leisure radars - see http://www.panbo.com/Pulse_Radar_Safety_courtesy_Navico.pdf as an example.

I wouldn't worry too much about being in the beam on the foredeck, but I would want the scanner above standing-on-the-seats head height at the cockpit.

Agreed, this is sensible, and is presumably why the Scanstrut poles, for instance, are at least 6ft high.

 

[pvb]

It does but because of a higher position to a lesser extent.

It's a long time since I studied geometry, but I can't see that a few metres extra height would make any significant difference.

 

[vyv_cox]

My scanner has been on a pole at the aft end for many years now, certainly more than ten. When we used it a lot, in the Netherlands, it seemed very effective, picking up ships in plenty of time to avoid them and useful for detecting buoys in some of the long channels. Nowadays in the Med I turn it on occasionally to check that it is still working and that I can remember how to operate it.

 

[prv]

But Raymarine also say "the energy absorbed from an ordinary mobile phone can be several times greater than that from a correctly installed Raymarine radar."

Note the careful insertion of "correctly installed". If it's installed as per their instructions, you will be out of the beam and therefore the energy you absorb will indeed be low. That was rather my point - make sure the pole is long enough that people can't stand with their heads in the beam. Not everybody uses a ready-made Scanstrut pole, and might end up mounting it too low if they don't consider this issue.

Pete

 

[pvb]

Note the careful insertion of "correctly installed". If it's installed as per their instructions, you will be out of the beam and therefore the energy you absorb will indeed be low. That was rather my point - make sure the pole is long enough that people can't stand with their heads in the beam. Not everybody uses a ready-made Scanstrut pole, and might end up mounting it too low if they don't consider this issue.

True, there are many custom-made poles, but most people are bright enough to get the radome positioned higher than the boom, which will minimise any health issues for people in the cockpit.

 

[wizard]

I had a pole mount on the rear of my yacht and range was never a problem crossing the channel several times each year. The problem I had was the ease with which they could be pinched. After I lost 2 over 3 years so I was forced to switch to a mast mount.

If you are in a secure location this will not be a problem though.

 

[johnalison]

I had a pole mount on the rear of my yacht and range was never a problem crossing the channel several times each year. The problem I had was the ease with which they could be pinched. After I lost 2 over 3 years so I was forced to switch to a mast mount.

If you are in a secure location this will not be a problem though.

That sounds very unusual, and more than a little irritating.

I've had my radar on a pole for many years, partly to keep the weight low. Range has never been a problem and we pick up ship from 15 miles +. On the other hand, I seldom use the radar when heeling since fog tends to occur in calm conditions mostly.

If you set the scanner well clear of the boom, this will usually be well out of harm's way.

 

[robmcg]

Thanks to all posters, especially those who have kindly posted photos of their pole mounted radars. Will look into a pole for ease of installation as the potential disadvantages can be minimised. Will take care to not nuke my head/eyes

Rob

 

[knuterikt]

Some more information to look at

Some interesting links

http://www.panbo.com/archives/2012/03/should_sailboat_radars_be_leveled_and_if_so_how.html

http://www.morganscloud.com/2008/04/01/radar-scanner-position/

There are lots of ready made kits available, have look around.

 

[William_H]

Radar radiation can harm human cells especially the sensitive cells.
However look at the numbers. A 4kilowatt radar will radiate in short pulses so average radiated power will be 5 to 10 watts.
The power is radiated in a narrow beam so in elevation about 12 degrees above and below the horizon. So 2 ft above the tallest head (in worst position) will mostly minimise radiation. Lastly the radar beam is rotating so average absorbsion of radiation in a head will be about 10% of actual power. (if radar beam stood still)
Yes high powered military radar has damaged people but boat leisure radar is much less dangerous. Just use your common sense. olewill

 

[lw395]

Radar radiation can harm human cells especially the sensitive cells.
However look at the numbers. A 4kilowatt radar will radiate in short pulses so average radiated power will be 5 to 10 watts.
The power is radiated in a narrow beam so in elevation about 12 degrees above and below the horizon. So 2 ft above the tallest head (in worst position) will mostly minimise radiation. Lastly the radar beam is rotating so average absorbsion of radiation in a head will be about 10% of actual power. (if radar beam stood still)
Yes high powered military radar has damaged people but boat leisure radar is much less dangerous. Just use your common sense. olewill

Why do you think only the average power matters?
Personally, I'd prefer to be fairly careful about being the main beam of a 4kW source, how much energy does it take to change a few strands of DNA?
Cell nuclei are small things that may be affected very quickly.
It's about field strength as well as simple heating.
It's not like microwaving a lump of meat, although some radar will do that to pigeons.
A 20 degree vertical beam angle spreads 12ft in the length of a medium size yacht, so anyone forward of the cockpit will be well in the beam.
Obviously the intensity drops as you get further from the antenna.
Common sense would actually suggest being cautious with things that are not fully understood!

 

[pvb]

Common sense would actually suggest being cautious with things that are not fully understood!

I don't think you've fully understood how minute is the risk from the average leisure radome.

 

[AntarcticPilot]

Radar radiation can harm human cells especially the sensitive cells.
However look at the numbers. A 4kilowatt radar will radiate in short pulses so average radiated power will be 5 to 10 watts.
The power is radiated in a narrow beam so in elevation about 12 degrees above and below the horizon. So 2 ft above the tallest head (in worst position) will mostly minimise radiation. Lastly the radar beam is rotating so average absorbsion of radiation in a head will be about 10% of actual power. (if radar beam stood still)
Yes high powered military radar has damaged people but boat leisure radar is much less dangerous. Just use your common sense. olewill

I've certainly worked near radars where getting anywhere near the radiating antennae was strictly off limits, especially if you wanted to have children! That was a DEW line radar on the Greenland Ice cap, though.

There is also a substantial safety zone around VSAT satellite communications antennae; several metres.