heres a "tutorial" (so to say) i found....
It's a long, 100-mile trip to the other side of the Gulf Stream to catch yellowfin tuna, and it's a big ocean for skippers out of Port Canaveral, Florida, like Capt. Mike Kane on White Water. Describing a recent - and pretty typical - trip, Kane says he gets the edge he needs from radar, in his case a 25-kilowatt Simrad. After studying the screen once they'd reached the grounds, Kane says, "I figured we had a school working some 8 miles off to the northeast." Sure enough, when they arrived at the spot, a flock of frigate birds was feeding over the sort of white-water explosions that signal tuna in a feeding frenzy. "Without the radar," Kane says, "we might have trolled around all day and never found that school." "When you're looking for a flock of birds out on open seas," says radar expert Steve Nusser, of Steve's Mobile Marine in Coral Gables, Florida, "there's no way a human being can see them 6 or 7 miles away with the naked eye." GEARING UP When a customer tells him he wants to see birds, Nusser says he raises the performance bar to a higher notch. He's installed a half-dozen 10-kilowatt Koden radars over the past year, all capable of spotting birds at 6 to 10 miles. Raytheon's newest radars with MagTronic technology, borrowed from the company's defense division, effectively doubles the reception range for the same power. For the first time, anglers can spot birds 4 to 6 miles off with a 4-kilowatt radar. Without this new technology, 4-kilowatt units simply lack the muscle to spot birds. This restricts the most effective bird-spotting radars to larger boats that have enough bridge space for bigger displays and are better equipped to accommodate the 4- to 6-foot antennas common to 10-kilowatt models. Since sea birds are small, relatively soft objects that return weak radar echoes, more power focused into a tight beam is needed to get a distinguishable echo, especially at longer ranges. Bigger CRT displays are called for because they provide the definition necessary to show small targets when set at longer-range scales. John Caballero, general manager of Simrad, suggests several factors to consider when buying a radar for fishing. "S-band radars are almost specifically designed for the purpose of detecting birds, but are way too expensive for most recreational anglers. But today's X-band radars have better transceivers and use advanced signal processing techniques. That makes them more than capable of displaying relatively low-flying birds at considerable distances. A buyer should inquire about a radar's output power, frequency, beam form, pulse repetition rate, pulse length, signal processing and display resolution, as these all combine in determining whether birds will appear on your screen or be invisible to your radar." Radars with more than 4 kilowatts of power generally include an open-array antenna with a narrower beam width and better overall signal output and return than smaller radome antennas. Most radome antennas have beam widths of 3 to 7 degrees while open-array antennas usually have tighter beam widths of about 2 degrees. The tighter the beam, the closer birds can be to each other and to the water and still be displayed separately. The wider the beam, the greater the tendency for a unit to blend targets that are close together into a single blob instead of showing them as individual marks. Ten-kilowatt, X-band radars with 12-, 15- and 20-inch displays are available from most of the major manufacturers. Nusser says that choosing the largest display that you have room to mount guarantees the best screen definition and gives you the best chance of spotting birds. FINE-TUNE FOR FEATHERS Today's radars have excellent auto-tuning features which match the antenna to the set, but the key to seeing birds is getting the gain setting exactly right, and that's something the angler has to do. "Turn it up until you start seeing false returns," Nusser advises, "then nudge it back down until they go away. The wrong gain setting can do the same thing that improper tuning does. If you have the gain set too low, there will be targets out there you won't see. If you turn it too high it will start showing you targets that don't exist." The proper gain setting necessary to see the cluster of specks that indicate birds is different on every installation because there are so many variables involved. Kane suggests starting with your gain set at maximum, and the sea clutter filter turned off. "Remember that the bigger the seas get, the less bird-spotting range your radar will have as well," he warns, "especially on lower-power units or boats with antennas closer to the water's surface." Kane also uses his unit to spot weed lines on flat-calm days. Here's a simple way to find the right setting: Have someone stand by with his boat near some birds and be ready to chum. Move apart the distance you want to spot birds on the radar and have him toss the chum and move off. As the birds swoop down, switch your radar to the minimum range scale that will reach them (to get the best possible screen resolution) and start tweaking the gain until you see the birds. Have the other boat stay within sight of the birds so you can get a running description of their actions by radio during the test. Try this at several ranges and under different sea conditions. You'll find the right gain setting for most fishing conditions while discovering the bird-spotting limits of your equipment. To test this without a second boat, or to test a smaller radar that probably won't show birds that are out of sight, you can spread the chum yourself and watch the birds on radar as you move slowly away. When the birds disappear from the display, you'll know that you've either passed your radar's maximum bird-spotting range or they've settled on the water after polishing off the chum.
Last edited by bluffman2; 09-17-2008 at 06:44 PM.
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