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#1
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Jeff Morris wrote in
: I've had minor second thoughts on this after checking the specs. In the "old days" more powerful domes were heavier and used more power - that is not the case now - the 4kW Raymarine dome only weighs a few pounds more and uses 1 or 2 Watts more juice. Pot metal and plastic is much lighter, which is what the Raymarine is made from. They'll replace it when the pot metal consumes itself from the condensation of breathing in and out through the drain tube makes it rain inside the dome, though. We're on our third...(sigh) The communications on the RL70CRC also failed, which explains why we couldn't get the Seatalk Gyro/Compass to ever calibrate properly, no matter how many times we turned it slowly. They fixed that, too, but I don't think it was ever working right in the first place. Isn't it amazing how 2,000 watts of peak RF power just appears from thin air for only 1-2 watts more DC? Magic? Divine intervention? Maybe its the printer stepper motor that turns the rubber band that drives the PC board antenna array...?? I'm still not sure of the value for long distance viewing, but the high power dome will have finer resolution, so that a pair of channel buoys will be resolved as two targets further away with the more powerful unit. Navigation is easier, since coastlines will more closely resemble the chart. However, this takes a lot of practice and you're better off relying on a good gps. Ah, but you have another problem in the fog. The higher the antenna, the further away the target will disappear as the target approaches the boat! You won't see the bouy 8 miles away with the antenna down low, but you WILL see the bouy in the fog a LOT closer to the boat as you, hopefully, pass it. Traveling at Mach 1, I'd understand having more range. But, traveling at 6 knots I'd rather see that target two boatlengths off the port bow with a lower-down antenna....wouldn't you? The downsides of the large unit is almost double the cost (a $1000 premium on the RayMarine list) and a much larger dome (an issue for those trying to hide the dome from the jib). I'm tired of changing out pot metal Raymarine antenna pods. There's gotta be a way to build a $2000 radar transceiver that isn't made out of the same materials as the window winder in a '97 Ford pickup. The damned chassis it's all mounted in is made of ZINC!! Idiots.... Look inside for yourselves! Don't trust me. Unscrew the 4 little flathead screws and take the top of the dome off. Do it on that boat down the dock and see if it's wet inside! Furuno? Anyone had water destroy a Furuno radar dome?? |
#2
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"Larry W4CSC" wrote in message Ah, but you have another problem in the fog. The higher the antenna, the further away the target will disappear as the target approaches the boat! You won't see the bouy 8 miles away with the antenna down low, but you WILL see the bouy in the fog a LOT closer to the boat as you, hopefully, pass it. Traveling at Mach 1, I'd understand having more range. But, traveling at 6 knots I'd rather see that target two boatlengths off the port bow with a lower-down antenna....wouldn't you? I have to wonder how serious a problem this really is. For instance, if I can run between two buoys spaced 300' with a scanner that's over 100' in the air and watch them pass down my side, how much difference can there be with a small boat and a scanner placed 30' up, unless you are totally crowding the buoy to one side (not good). Also, by that point, if you lose sight of the buoy, you should have all ready changed your concentration to some new point or reference, ahead. otn |
#3
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In article . net,
"otnmbrd" wrote: I have to wonder how serious a problem this really is. For instance, if I can run between two buoys spaced 300' with a scanner that's over 100' in the air and watch them pass down my side, how much difference can there be with a small boat and a scanner placed 30' up, unless you are totally crowding the buoy to one side (not good). Also, by that point, if you lose sight of the buoy, you should have all ready changed your concentration to some new point or reference, ahead. otn OTN, the Horozontal Beamwidth of your Commercial Maritime Radar is significantly smaller than that of the units found on most Pleasure type vessels. That makes a HUGH difference in the Target Discrimination Ability between the two radars. Apples and Oranges, here....... Bruced in alaska -- add a 2 before @ |
#4
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"Bruce in Alaska" wrote in message news: OTN, the Horozontal Beamwidth of your Commercial Maritime Radar is significantly smaller than that of the units found on most Pleasure type vessels. That makes a HUGH difference in the Target Discrimination Ability between the two radars. Apples and Oranges, here....... Bruced in alaska This I understand. However, and here I need to be careful to note that my comments are not technical, rather, practical experience based, dating back to Decca 101's and KH 17's , on multiple size/type vessels ...... I've rarely experienced a serious problem with close aboard, lost targets that would negatively impact the navigational procedure I was using, including docking. Admittedly, some units were better than others, either due to the basic unit and/or it's condition and you needed to adjust some procedures, but, my point is that you don't want to consider a radar's use "drop dead useless" below a certain range, based on pure technical data, without first checking your particular unit under real conditions to see if they apply or are indeed a problem. MOFWIW otn |
#5
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In article et,
"otnmbrd" wrote: This I understand. However, and here I need to be careful to note that my comments are not technical, rather, practical experience based, dating back to Decca 101's and KH 17's , on multiple size/type vessels ...... I've rarely experienced a serious problem with close aboard, lost targets that would negatively impact the navigational procedure I was using, including docking. Admittedly, some units were better than others, either due to the basic unit and/or it's condition and you needed to adjust some procedures, but, my point is that you don't want to consider a radar's use "drop dead useless" below a certain range, based on pure technical data, without first checking your particular unit under real conditions to see if they apply or are indeed a problem. MOFWIW otn Yep, I'll go along with that...... Bruce in alaska -- add a 2 before @ |
#6
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On Tue, 15 Feb 2005 07:38:34 GMT, "otnmbrd"
wrote: "Larry W4CSC" wrote in message Ah, but you have another problem in the fog. The higher the antenna, the further away the target will disappear as the target approaches the boat! You won't see the bouy 8 miles away with the antenna down low, but you WILL see the bouy in the fog a LOT closer to the boat as you, hopefully, pass it. Traveling at Mach 1, I'd understand having more range. But, traveling at 6 knots I'd rather see that target two boatlengths off the port bow with a lower-down antenna....wouldn't you? I have to wonder how serious a problem this really is. For instance, if I can run between two buoys spaced 300' with a scanner that's over 100' in the air and watch them pass down my side, how much difference can there be with a small boat and a scanner placed 30' up, unless you are totally crowding the buoy to one side (not good). Also, by that point, if you lose sight of the buoy, you should have all ready changed your concentration to some new point or reference, ahead. It is a big problem with small-craft radars, in my experience. The vertical angle is nothing like what you describe on the Furuno and Raytheon units I have used. Rodney Myrvaagnes Opionated old geezer Faith-based economics: It's deja voodoo all over again |
#7
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On Tue, 15 Feb 2005 04:44:49 GMT, Larry W4CSC wrote:
Furuno? Anyone had water destroy a Furuno radar dome?? OK, crap construction drives me nuts, particularly when it's something (like a radar) which MUST spend its working life out in the elements. Assuming the radar itself isn't absolute crap...like that "Mars Bar" radar the Brits made 25 years ago, say...what is *your* radar of choice for durability? 'Cause once I go up the mast, I don't want anything short of a hurricane to cause damage to that radome... My buddy swears by his old Kodan CRT unit, but he's got a big ketch and more room and power than most people to play with. The thing is a toaster-sized box bolted to his coaming, and it takes skill to use it, but if you can learn that skill, it's accurate as hell. R. |
#8
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In article ,
rhys wrote: On Tue, 15 Feb 2005 04:44:49 GMT, Larry W4CSC wrote: Furuno? Anyone had water destroy a Furuno radar dome?? OK, crap construction drives me nuts, particularly when it's something (like a radar) which MUST spend its working life out in the elements. Assuming the radar itself isn't absolute crap...like that "Mars Bar" radar the Brits made 25 years ago, say...what is *your* radar of choice for durability? 'Cause once I go up the mast, I don't want anything short of a hurricane to cause damage to that radome... My buddy swears by his old Kodan CRT unit, but he's got a big ketch and more room and power than most people to play with. The thing is a toaster-sized box bolted to his coaming, and it takes skill to use it, but if you can learn that skill, it's accurate as hell. R. Give me a Furuno, over any other third and fourth generation Radar OEM and a Decca over any second generation Radar. First generation radars were all crap, and the fifth generation is just now coming out, so no one knows yet who has the best stuff....... Bruce in alaska -- add a 2 before @ |
#9
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On Tue, 15 Feb 2005 04:44:49 GMT, Larry W4CSC wrote:
Isn't it amazing how 2,000 watts of peak RF power just appears from thin air for only 1-2 watts more DC? Magic? Divine intervention? Maybe its the printer stepper motor that turns the rubber band that drives the PC board antenna array...?? Not sure about the merits of this beef. A radar with a pulse repetition period of 1 millisecond, and a pulse width of 1 microsecond has a peak power about a thousand times greater than its mean power - and this is a standard feature of pulse radars.... Brian Whatcott Altus OK |
#10
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Think "watt-seconds".
2000 watts for 2 microseconds requires 4 watt-milliseconds or 0.004 watt-seconds. Throw in the PRF, and the rest is heat. Roger http://derbyrm.mystarband.net/default.htm "Larry W4CSC" wrote in message ... snip Isn't it amazing how 2,000 watts of peak RF power just appears from thin air for only 1-2 watts more DC? Magic? Divine intervention? Maybe its the printer stepper motor that turns the rubber band that drives the PC board antenna array...?? |
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