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#21
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In article ,
"Steve Lusardi" wrote: The Furuno is a fairly inexpensive RADAR and yet according to you, it is doing nearly impossible things. Joe, You are correct, it does, but it's good if it can. 80 nano sec. is quick. Many of the commercial sets cannot. Steve 80 nanoseconds isn't all that quick, in Xband, with SolidState Receiver Frontends, Ring Circulators instead of the old T/R Cells of yesteryear, and SolidState Modulator Strings instead of the old 2E25 Tube modulators of yesteryear. Third and fourth generation commerical marine radars, have been doing this good, for at least 20 years. What many "commercial sets" can't do, is overcome the cheap design tradeoffs that most OEM's have made to keep their equipment affordable to the guy who only runs his yatch once or twice a year. If you pay the price for a good marine radar, you will get the preformance that your looking for. If not you will get what the Yatch Club Crowd, thinks they should have to pay. $5kUS buys a reasonable marine radar, and $10KUS buys you what you really want, but can't justify to the MRS....... Commercial Operators buy the later........ Bruce in alaska -- add a 2 before @ |
#22
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On Fri, 06 Jan 2006 20:41:10 GMT, Bruce in Alaska
wrote: Of course you have to remember that the KR-124 was a true 9Kw radar, with a real good slotline 3Ft antenna, an excellent Logrythmic IF Strip, and brand new 1N415E Crystals. Good story. My Furuno is a fairly ordinary consumer grade Navnet model but we pick up birds all the time on the close in ranges. Not sure about styrofoam cups but wooden row boats are no problem. No service required in the first year even though I installed it myself. We're happy. |
#23
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Wayne.B wrote in
: And that will tell you about the 16 ft Boston Whaler fishing in the fog bank right in front of you? No, and neither will the radar scanner at 55 ft as some suggest to get long range. Boston Whalers with little metal are hard to detect. Of course, if we were to make $99 AIS transponders MANDATORY, problem solved. |
#24
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On Fri, 06 Jan 2006 23:38:05 -0500, Larry wrote:
No, and neither will the radar scanner at 55 ft as some suggest to get long range. Boston Whalers with little metal are hard to detect. ====================================== We have no problem picking up small boats with the scanner at 24 ft. It is unlikely that mandatory AIS will ever become a reality for boats under 30 ft or so, perhaps even larger. |
#25
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No, and neither will the radar scanner at 55 ft as some suggest to get long
range. Boston Whalers with little metal are hard to detect. Wayne.B wrote: We have no problem picking up small boats with the scanner at 24 ft. It is unlikely that mandatory AIS will ever become a reality for boats under 30 ft or so, perhaps even larger. And if it is made mandatory for pleasure boats, how many people will still not have it, or forget to turn it on, or leave it broken? DSK |
#26
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On Fri, 06 Jan 2006 20:41:10 GMT, Bruce in Alaska
wrote: Ok, I feel a Furuno Story coming on....... Many years ago (1975) I installed one of the first Furuno KR-124 Radars imported into the US, on a 85' Yatch in Lake Union, Seattle, Washington. This vessel had a Professional Skipper & Crew. (ex coastie) Takes about 3 hours if the antenna, and display are already mounted, and the interconnect cable is already run but not terminated. Skipper was a sharpeyed older gent, who wasn't sure that this kid,( myself) knew anything about "Anything", and was determined to keep an eye on the whole process. Got everything connected and fired up the radar, to do the Sea Trial, and get the Heading Flash Reed Switch set to ships head. Nice clear amazing picture on that analog display. As we were pulling away from the dock, the skipper looks at the display and asks, "What is all that clutter, down here in the port quadrant at .25 miles?". I look, and see a bunch of targets, close together, and then look out with a set of Binocs, and see a small group of Seagulls sitting on the water. "It is that group of Gull's over there" says I. He says, "Bull ****". "No", says I, "Wait till that seaplane taxi's over there, and they all take flight, and the targets will all disappear of the scope". Sure enough the Seaplane taxi's right thru the group, and all the targets disappear from the scope except one. "Look, see they all disapperaed, just like I said" skipper looks in the scope and says, "Nope, kid there is still one target there". "Well", says I, "There MUST be something in the water, over there". Skipper says "Bull ****, I can't see anything there with these glasses, but we'll just cruise on over and look." So we idle on over, and sure enough, here is a styrofoam cup floating in the water. We pick it up, ad set course for the Can, right off GasWorks Park to use as a Heading Flash setup target, and sure enough when we get .25 Miles from where the cup was, the skipper checks the scope and no more target. "Hell, that is one great Radar to be able to pick up a strofoam cup at a quarter mile. Never had that kind of luck with any of my Raytheon Radars". I just smiled......... Of course you have to remember that the KR-124 was a true 9Kw radar, with a real good slotline 3Ft antenna, an excellent Logrythmic IF Strip, and brand new 1N415E Crystals. When compared to what was out in the fleet at the time, (Raytheon 1500's,1700's 1900's and Decca 101's and 202's) this was an order of magnitude leap in commercial radar technology. And it didn't require ANY service for years at a time, which really made the semi-monthly Raytheon Service look BAD. That radar and it's follow on KR-248, and KR-448 is what MADE the Furuno Name in the High Seas Fishing Fleets and North Pacific Coastal Freight Fleets. Bruce in alaska Thanks for sharing that fun story - it must be a rare bird - a radar story..... Brian Whatcott Altus OK |
#27
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Wayne.B wrote:
On Fri, 06 Jan 2006 23:38:05 -0500, Larry wrote: No, and neither will the radar scanner at 55 ft as some suggest to get long range. Boston Whalers with little metal are hard to detect. ====================================== We have no problem picking up small boats with the scanner at 24 ft. It is unlikely that mandatory AIS will ever become a reality for boats under 30 ft or so, perhaps even larger. It won't be mandatory for everything. Kayaks, 14' alu boats, logs. Radar is still better. Gaz |
#28
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i am reminded of the guy with an early handheld plotting GPS walking around
in ten foot circles saying, "look, it tracks me exactly".....pre SA! I am a relative newcomer to radar and use a digital RADAR-PC setup and during the day i can imagine i am seeing all manner of things that show up on my screen...if it is flat calm and the gain is high enough and the sewa clutter is OFF....but at night in the fog healed 20Deg that dot that appears for one scan...then mis and then two scans again then gone will have you staring at the screen instead of looking ahead to see if it is a contact or a wave or a ghost reflection from your rigging or even the bouy at 90degrees from the blip. What about sidelobe reflections which are again reflected and recieved...they are only interpretable after the fact...not a priori..? they are lower in intensity and can look like a small contact in any place. The receiver knows only when it switched from transmit to receive [time] and the radial angle of the antenae at that time so a reflected signal appears only to have been recieved from a distance equivelent to the total pathlength and in a direction in a straight line perp to the face of the antenae at that moment of capture...a ghost image. Then when you get a circular series of large contacts you may well wonder what semi circular beast is ahead of you.... read a book about the propagation of radar microwaves and see all the ways a blip can mislead you and thank God the guy you almost mowed over didn;t have radar and was keeping a lookout. Radar assisted collision are a significant reality. Real life radar is a tool that must be interpreted and i am finding out it takes a LOT of interpretation and experience to be able to rely on it more so than your eyes. The mainbang is suppressed so you don;t see the big donut around your boat extending for 200ft on a 1/2 mile range...if you are at 1/8th mile you might see a target at 50ft but only if the mainbang is not supressed and the gain turned way down and the sea clutter way up to exponentially deminish the gain applied to close returns. As for styrofoam cups....the intensity of an electromagnetic wave falls off in a cubic [3rd power] manner relative to distance and the reflected wave similarly diminishes but the part reflected is only that portion perfectly perpendicular to the antenae...as it dips and turns on a weaving mast even less of it is oriented in a 'perfect' manner. The intensity of the emmitted electromagnetic field recieived by the antenna is so small it is a marvel that modern electronics can even discriminate it from the background noise. Now the clincher....what portion on the emitted signal would a round styrofoam cup reflect from half amile away? hint, styrofoam is not a reflector of electromagnetic energy..is it an insulator and absorbs microwave energy. the only reflection would be from moisture in a thin lhorizontal line...perpendicular to the antena and the relfected signal is likely a billionth of the emmitted signal at best. Granted there are galenium arsenide semiconductor equiped ultra low noise receivers that could discriminate that SNR but at a few thousand dollars in the hands of a relatively untrained operator the pleasure boat operators radar.....it makes for good bench racing stories but little more. AND...if you really are detecting the water on a birds wings i suggest you tune and adjust the radar to pick up and discriminate larger targets...else they will be lost in the clutter In the process of ruining a 'story' i hope to have saved someones life by stimulating you to really learn what a radar can and can't do...repeatably. Quod erat...you know the rest of the story. rick "DSK" wrote in message ... No, and neither will the radar scanner at 55 ft as some suggest to get long range. Boston Whalers with little metal are hard to detect. Wayne.B wrote: We have no problem picking up small boats with the scanner at 24 ft. It is unlikely that mandatory AIS will ever become a reality for boats under 30 ft or so, perhaps even larger. And if it is made mandatory for pleasure boats, how many people will still not have it, or forget to turn it on, or leave it broken? DSK |
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