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Radar Mast
Here is one for the tractor board! The boat I am currently refurbishing came with a radar unit mounted on a homemade radar arch. It was a disgusting looking thing welded from square stock aluminum with little regard for appearance. It conformed nicely to the butcher job on the wiring and interior, I left it at the marina prior to having the craft hauled to my barn. I fired up the batteries today after cleaning all connections and removing rube goldberg additions to the factory harness, still plenty of cleaning up to do but it at least appears safe to use now. Since I have never owned a vessel with marine radar, I am wondering if I can mount the antenna above the cabin without degrading the signal forward. I realize I will lose the functionality of the rear 1/3 of the unit due to interference from the fly bridge, but I can live with that. Perhaps Murf might have experience with one of these?
Thanks,
Cutter
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Radar Mast
Somebody called?
Depending on the unit it may or may not work in that position, some units will shut down the receiver if there is too strong a bounce back the transmitter.
Is there no way to mount the unit over the fly bridge? Of course the higher the unit is mounted the better the performance will be also.
Even a simple tripod type mount can be made easily and does not have to be 'professionally' made to be effective and easy on the eyes. The most common (and easiest to make) is a single vertical pole braced by two forward pole going out & down at a 45 degree angle to the first. The vertical can be mounted atthe front centre of the fly bridge and the supports on each corner of the cabin itself. If you want to cheat just a little, any welding shop that does aluminum or stainless TIG can make the brackets for each base and the junction point then just cut tubing to lenght and use stainless nuts and bolts to put it together.
Best of luck.
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Radar Mast
Do you want the microwave radiation beamed on the bridge area? I am not sure what the wattage power of these systems are but having watched birds fly near the military arrays what happens quickly can cook you more slowly.
Peters
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Radar Mast
They are relatively low power units since they are designed to be used near people and in situations where they may accidental be left on in situations where they are nearly pointed at someone, such as in adjoining slips at a marina.
My unit is fairly powerful by comparison to other units available, it has a maximum output power of 4.0 Kw., the average unit has a 2.0 Kw. output.
Still probably not a great thing to have mounted in front of you.
Best of luck.
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Radar Mast
Most marine radars generate a dangerous amount of radio frequency energy. Your eyes are particularly sensitive to this frequency of radiation. You want to mount radar high and in the clear. The beam is fairly narrow, so there is little danger if it is mounted a foot or two over your head. But you never want to be within a few feet of the front of the horn when it is operating. Even a few hundred watts of power is dangerous in this frequency range.
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Radar Mast
You are correct in stating the dangers of the radio frequency. You can go blind having it in your constant view. Remember when police used to lay the guns in their laps while waiting for speeders. Allot of cops got cancer of the XXXs. Our other engineer at the shop is a member of the Power Squadron(Boat guys). He'll bring in some tech info from their books. I'll post it tomorrow if he remembers.
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Radar Mast
Mike is absolutely right. You do NOT want to be sweeping the bridge area with radar microwave radiation. Not a good thing. It may not be of the wattage output of a miltary radar but you are not doing your body any favors exposing yourself to it. There were areas aboard ship that nobody was allowed and deck border warning areas were painted while the ship radar was in operation. Mount the radar antenna high enough to allow a safe distance above the bridge area and restrict the radiation output to above you heads. If you don't think this is a radiation hazard, just ask some policement who used earlier radar speed guns in their cruisers and kept the gun between their legs when not clocking vehicles. I am sure some of the law enforcement guys on the board with jump in here.
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Radar Mast
There was a boat owner in the marina I used to use periodically on Georgian Bay (which is notorious for bad weather which comes up FAST) who used to leave his radar on while the boat was tied up in his slip.
His logic was he didn't want to be in a covered slip, he wanted to enjoy the sun, but he didn't want to be 'surprised' by a thunder-storm....
The management (less than politely) told him to either leave it off or get out.
Best of luck.
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Radar Mast
In the early days of RADAR, technicians adjusted the equipment for maximum output by putting their arms into the beam and feeling the "warmth." You could substitute the word "cooking" for warmth. These early sytstems used longer wavelengths working into large dish antennae. Todays marine radars combine very high power pulses into a very small aperture. Powers typically range between 2000 to 4000 watts. Microwave ovens are often rated for 750W.
A microwave oven and a marine radar are different because one is intended to maximize the heating effect, but both work on tissue the same way. One of my old amateur radio transmitters had an effective radiated power of just over a megawatt and it could knock birds out of the air. (This was pointed upward and was used to bounce signals off the face of the Moon.) The equipment had automatic shutdown switches so that you could not be inadvertantly exposed through an open access panel or port.
Diathermy used to be used for deep tissue heating, but that has now been largely replaced by ultrasound treatments which are much safer. Diathermy uses the same sort of RF tissue heating but at a much lower frequency and power level. As I said in a previous post, the eyes are the most sensitive organs in the body to this sort of damage, so never look into a radar horn.
Distance from the horn is also important. You get 0.1% of the RF exposure at 300 ft that you get at 10 feet from the radar source. This follows the square law for distance.
I am not sure of the power levels used by early police radar guns. Today the high efficiency doppler units can transmit pulses of just a watt or less. Still, I would not want to put one too near my cajones.
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Thanks for all the input :> on the subject. I was unsure if the windshield was a sufficient deterrent for the signal, but is sounds as though it is not. I did not realize they were quite so harmful as I have seen these units deck mounted on short struts. I have tossed the manufacture of the arch around in my head all day and had pretty much decided that is what I will do prior to reading all of these posts. I like the tripod idea Murf. I had thought of bending aluminum pipe, raking it rearward and welding a plate to the top center of the rig. I can bracket it in on the sides of the bridge, not much weight to support with just the antenna on it. I will have to play with some designs.
Thanks again!
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01-03-2004, 20:14 
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