saw this on another site so i thought you guys might like it
Marine RADAR basics
I am not a RADAR technician but I have worked with RADAR for the past 30+ years as an Air traffic Controller. I picked up a few things along the way, and I slept at a Holiday Inn Express last night J
Anyone else is welcome to chime in with corrections and additions. I donít fully understand it all but I have a good basic understanding. I speak mostly about traditional radar, the newer HD and HD Color systems I havenít read up on too much as of yet but all in all they work pretty much the same. I think the use different frequencies and have better display processing.
First, Radar has a couple basic parts ,the Transmitter, Magnetron, which creates focuses and transmits the signal out, a timer and receivers and a rotator. Lots of other complicated electronics. Signal processing for the most part is done in the display unit. You need a combination of a good transmitter array and signal processor to have a good working system.
The Rotor is just as important as the rest, its critical in the timing of the signal. A malfunctioning rotor will ruin the system. One of the reasons I prefer a dome unit, I donít have to worry about birds sitting on it or gunking it up so it doesnít spin freely.
So basically the magnetron shoots out a signal, a timer switches back and forth between transmit and listen (very rapidly) the receivers listen and send the return signal to the processor which makes since of it all and creates the display. One of the things I did when I installed my system was put the radar on a separate switch so I can switch it completely off when anchored up or sitting at the dock. Even in standby, the array pulls between 25-30 watts. Check your manual to see what yours pulls. It does this to keep the magnetron warmed up. Even in stand by your clock is counting down on Magnatron life. Most have a life of 2-3 thousand hours. If you think thatís a lot, think about how many hours you work a year, for most its 2080. Does yours still work after 3000 hours, maybe but the signal is being degraded. Will a high end FURUNO commercial maggie last longer, you bet, will a GARMIN?? They range from 300-500$ not including installation if you canít do it.
Range: On a downeast boat, a unit mounted to a modest tower regardless of KW strength or array size, you have at best 6-10 mile range AT BEST. There is a calculator on the FURUNO web site to calculate RADAR range you can see. Base on height of your RADAR above surface and the height of the object or target. It really bugs me they even put 48 mile range on these things.
One of the biggest things fisherman want to see is birds. The magnetron in your RADAR is for the most part the same as your microwave, they cook chickens so well because the chicken absorbs the microwaves and heats up. Its how your kitchen microwave was invented, by a couple RADAR engineers at Raytheon. Sea birds dive, and they get moister on their wings and bodies and start reflecting RADAR back. The higher the density of birds the better the return. Some of the newer HD RADARs have a bird mode, not sure exactly what frequencies or voodoo they use in theses and how they differ from traditional but they do get a better returns on the diplay.
ARRAY size- Size matters only in the fact that a longer array is capable of receiving a little better resolution because it has more receivers along the array but its best for distance. Youíll have to look up the different Manufactures specs to see just how many receivers they put along the array. Its relative to distance and signal return time. Since most of us can only see 6-10 miles a 24 inch dome is plenty.
I guess thatís enough, If I have made any mistakes or misunderstandings or just plain wrong let me know I love to learn. Please add.