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Radar, tune, gain, sea, rain
Can any one give guidance or know of a possible
internet download that might help in the initial manual settings of tune, pulse width, gain, sea and rain clutter. The controls seem so inter-reactory, by their adjustment to my eye identical echo images are displayed. Even with tune I cannot really determine any great changes. There must be some logical progression to make these adjustments rather than my constant tweaking, all guidance greatly received. Beryl. |
#2
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"beryl george" wrote in message ... Can any one give guidance or know of a possible internet download that might help in the initial manual settings of tune, pulse width, gain, sea and rain clutter. The controls seem so inter-reactory, by their adjustment to my eye identical echo images are displayed. Even with tune I cannot really determine any great changes. There must be some logical progression to make these adjustments rather than my constant tweaking, all guidance greatly received. Beryl. Beryl, you might try going to the Furuno web site and downloading one of their radar manuals. www.furuno.com Most of their manuals explain the use of the controls you are asking about and come with tips for their use. |
#3
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In article ,
beryl george wrote: Can any one give guidance or know of a possible internet download that might help in the initial manual settings of tune, pulse width, gain, sea and rain clutter. The controls seem so inter-reactory, by their adjustment to my eye identical echo images are displayed. Even with tune I cannot really determine any great changes. There must be some logical progression to make these adjustments rather than my constant tweaking, all guidance greatly received. Beryl. Most commercial Marine Radars do not have user adjustable Pulsewidth Controls. They usually just pick two or three Plusewidths, designed for that Modulator/Range Switch Setting and leave it at that. Also, there are big differences in todays Radars, that use digital displays, than the analog displays of 20 years ago, and these can effect the adjustments your asking about. In most cases Rain Clutter should be left at minimum, unless you are actually painting a Rain Squall. Sea Clutter will also be set at some minimum setting, untill Sea Return from local (2 miles or less) waves begins to mask close in targets. I always liked to run the RF Gain at a level where the Noise Sparkles are just slightly noticeable. This would be for an analog display of yesteryear, but with LogRythemic Receivers. Modern Digital Displays are a bit different and I don't have enough time on them, to have an opinion. Tuning is a function of Magnitron Age, and the radar should be setup, so as the Tuning Peak is in the center of the Tuning Range of the External Control. This will drift over time (100's of hours) as the Magnitron ages, but the Tuning Peak can be moved back to the center of the External Control, by readjusting an internal control in most display units. Bruce in alaska -- add a 2 before @ |
#4
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On Thu, 25 Aug 2005 21:34:35 GMT, beryl george
wrote: Can any one give guidance or know of a possible internet download that might help in the initial manual settings of tune, pulse width, gain, sea and rain clutter. The controls seem so inter-reactory, by their adjustment to my eye identical echo images are displayed. Even with tune I cannot really determine any great changes. There must be some logical progression to make these adjustments rather than my constant tweaking, all guidance greatly received. Beryl. My JRC 1500 radar has an "auto-tune" setting - I leave that on, so I don't have to worry about tuning. I think the Sea and Rain settings are at zero, or very low - you don't need to turn up the rain control, unless you are in heavy rain that is masking targets. Turn the Sea control up just enough that sea returns aren't masking real targets. I set the gain just below the point where noise specks appear on the display - the gain may have to be adjusted a bit as you change ranges. -- Peter Bennett, VE7CEI peterbb4 (at) interchange.ubc.ca new newsgroup users info : http://vancouver-webpages.com/nnq GPS and NMEA info: http://vancouver-webpages.com/peter Vancouver Power Squadron: http://vancouver.powersquadron.ca |
#5
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beryl george wrote:
Can any one give guidance or know of a possible internet download that might help in the initial manual settings of tune, pulse width, gain, sea and rain clutter. The controls seem so inter-reactory, by their adjustment to my eye identical echo images are displayed. Even with tune I cannot really determine any great changes. There must be some logical progression to make these adjustments rather than my constant tweaking, all guidance greatly received. Beryl. A simple way to remember it is to adjust the major controls in alphabetical order. Brightness, Gain, then Tune. Leave sea and rain clutter completely off until you are in a situation when you need them and the other variables have been set. Paul |
#6
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beryl george wrote in
: Can any one give guidance or know of a possible internet download that might help in the initial manual settings of tune, pulse width, gain, sea and rain clutter. The controls seem so inter-reactory, by their adjustment to my eye identical echo images are displayed. Even with tune I cannot really determine any great changes. There must be some logical progression to make these adjustments rather than my constant tweaking, all guidance greatly received. Beryl. Tune - tunes the receiver frequency to the transmitter's frequency. You'll only see any difference on very weak targets, like a bouy way off in the distance, but over the horizon. Radar is very widebanded, as is its receiver. Tuning is very broad because of this. Find a very weak target that barely makes a dot as far off as you can see anything. Tune it for maximum return, then leave it alone....tuning done. If it has automatic tuning, just leave it on. Electronics tunes better without you. Pulse width determines how long the radar transmitter stays on during its transmission period. During the transmitting, the receiver is turned off. The pulse width, how long it keeps transmitting in microseconds, determines how long the receiver is turned off...on the screen this is measured from the boat in the center of the display outward. The shorter the pulse width, the CLOSER the radar can see near the boat....like that bouy we're about to run over in the fog. The narrower pulse width also is part of how FAR the radar can "see". A narrow pulse is less likely to get a good return off a far target thrashing about in the waves than a wide pulse width, which increases our chances of getting a return the receiver can detect. So, if we want to see the bouy 100 yards away, we use a very narrow pulse width. If we want to see a tower 12 miles away, we use a wide pulse width. Modern radars now adjust their pulse widths, automatically, when you change ranges on the display to optimize this setting. When the radar is on the 12 mile range, the narrow pulse width produces so narrow a "target blip" as to be near unreadable. The wide pulse width makes a wider, more easily seen target, on such a long range. It shows up in thickness from the center of the screen to the edge (that's time on the display). Gain is how sensitive the receiver is. It's like a video volume control, what the receiver sees. Modern radars are, again, automatic to produce a display of the targets, without too much gain, which displays white noise as false target spots at random. Turn the gain up until you see a bunch of clutter, then reduce it back until the clutter just disappears and the targets are all you can see. At night, you can raise the gain a bit as the thermal noise caused by the sun radiating off everything, including the antenna parts it heats, drops. You'll have to reduce it again in the daytime as the thermal noise starts producing clutter, again. Rainstorms also make lots of clutter, drop the gain to a point where the rain doesn't wipe out the targets. This is all analog, you know...even if you've a digital display unit. Sea and Rain clutter filters are sort of like the treble control on your stereo. They filter out fast returns caused by the radar bouncing off wave tops and rain drops, but let the big targets like ships and boats still show up. If you set them too high, they filter out everything and you run over that damned bouy we were headed for in the fog. Turn them up just enough to reduce the clutter to a reasonable level. They're not very effective. New radars have digital signal processing that only shows you targets that act like ships/boats/bouys....repetitive echos that appear to come from still or slow-moving targets. Random returns that don't repeat all the time are simply not sent to the digital display. Much improvement...vast improvement. They're also automatic from the smartassed electronics. Does this help? Not to worry....The world is going to help you with AIS.... http://www.nasamarine.com/AIS/AIS.html http://www.jrcamerica.com/product.as...311&l1=5311&l2 = http://www.ozsay.com/urun.asp?prod_id=412 http://www.mcga.gov.uk/c4mca/mcga-ml...DE77872207FE9A http://www.panbo.com/yae/archives/cat_ais.html http://www.navcen.uscg.gov/enav/ais/default.htm AIS provides you with, on each target: • MMSI (Maritime Mobile Service Identity) • IMO Number (where available) • Call sign & vessel name • Length and beam • Type of ship • Location of position-fixing antenna on ship • Ship's position with accuracy indication and integrity status • UTC • COG, SOG and Heading • ROT (Rate of Turn) where available • Ship's draught • Navigation status • Hazardous cargo (type) • Destination and ETA (at captain's discretion) • Short safety-related messages and free messages Wanna watch AIS LIVE! on the net? Europe is online at: http://aisfree.aislive.com/ really cool...AIS is on VHF and you get a target EVEN AROUND THE BEND! -- Larry |
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