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INTRODUCTION
Odds are your sonar has been mostly a bottom finder. Most of us just turned it on and take whatever it seems willing to tell us. The manual was boring and didn’t seem to connect much to real life scenarios. The demo mode always has nice fish arches and cool structure, but never on my screen. If that’s you, read on. I want to try making sonar easy toward better fishing. I highly recommend visiting the following web site for some basic information. It’s a great introduction to the subject.
http://webpages.charter.net/abshire5078/Chart tutorial.doc
Now that you’ve learned so much already, let’s think through the tool we’re trying to use. I have a 10-cell flashlight that shines a powerful small light beam surrounded by a floodlight. The center spot is really bright. The floodlight tapers off the farther from center it shines. Pointing that light down into the lake will make a cone of light shaped like a cone of sound broadcast from a sonar transducer. A small area of lake bottom would be illuminated brightly, the outer edges of light dissolving. The sound from a transducer is most powerful directly under it. The cone of a 20 degree transducer covers an area of lake bottom about 1/3 its depth, so in 100 feet the cone covers an area roughly 30 feet in diameter. But the real power is in a smaller center spot about 10 feet wide, everything outside that center in the fringe. The entire cone is like a stack of cones, the inner cone the strongest, each cone farther away from the cone axis a little weaker. It’s important to bring all that together to remember the following conclusions when using a sonar fish finder. Whatever is directly below a transducer will reflect back a strong echo. The deeper it is the longer it takes for the echo to return. Whatever is in the center cone will be reflected back stronger and sooner than anything outside that center strongest cone. Maybe now you can understand why a fish 5 feet off to the side of the cone axis and only 5 feet deep can return less of a signal as one 40 feet down directly under the transducer. The closer the stronger, but with loss of strength with increased angle away from the cone axis. That explains why you can pass directly over a large shallow fish that won’t show on the screen. It was too far out in the fringe area. At 5 feet depth the cone couldn’t be over 2 feet in diameter, so you would have to be right on that fish to display it. Yet, a school of bass is easily displayed 80 feet down.
Sonar readily "sees" the air bladder in a fish as easily as air bubbles floating up from bottom show up on screen, but also can detects their scales and fins to a lesser degree. The flesh of a fish is too close to the refractive index of water for it to distinguish the majority of a fish’s bulk. Some species have large air bladders so their arch is more pronounced than others. The closer the transducer gets to the air bladder the thicker the arch display.
By the way, one way to diagnose some fish species on sonar is to note how quickly it can swim up a great distance. A lake trout can do that easily because of a duct that regulates it's bladder. A walleye, however, must take time to burp air out to swim up quickly, the reason you should never horse a walleye from deep to shallow if you intend to release it. Let it burp its way up and there will be much less lactic acid and other gas bubble buildup in its bloodstream, and much more likely to survive to be released or stored in a livewell. Find out what your favorite fish species' air bladder characteristics are to better manage finding and handling them.
I read back through the document and decided to clarify a point or two. When a signal first appears on the right side of the screen, keep in mind it contains all echoes in a 360 degree range around the transducer. Most of what you see is going to be toward the edges of the cone, including the best signal from directly below the transducer. That's why a fish appearing on the screen probably isn't directly beneath the boat, but it appears that way. That's why it's important to compare round topped arches to sharp bent arches. It pays to study those pictures to learn the two arch shapes.
Another point is not to be discouraged over the emphasis on a color display. For obvious reasons that's much better than grayscale. I know. I've used grayscale many years and now color, and won't consider going back, but I could get along with grayscale just fine if fishing out of your boat using that display. We’re going to get into color later in another chapter. The document information applies to all display types. You can interpret the colors as variations of gray on your grayscale display. What shows up in color would appear as simply lighter or darker on grayscale. The stronger the echo, the stronger the colors. If you use grayscale you'll just have to spend more time examining the display. This also would apply to portable units hanging off a dock or tossed out from a shore. The basic principles are all the same regardless.
The display in the document is high resolution. Your unit might not be able to match that, showing blocks of images. That's a definite handicap. Might as well say that, it's fact. Do your best to come up with a 480 X 480 pixel display or better. It's the best place to put your hard earned money, above power, above screen size, or any other sonar feature including color. I'd rather have a 3" wide screen at high resolution than a 10" screen with 280 X 280 pixels. It would be no different than choosing a 40” screen TV with a very poor grainy picture over a 14” screen with excellent quality images.
To see fish arches:
1. Turn off Fish ID. The sooner you give that up the more you will get from sonar. With ID turned on you will be targeting debris galore and occasionally discover some fish.
2. Minimum noise on sonar screen. Not excess dots and meaningless lines all over. Remove all sources of electrical interference.
3. Hot battery for strong signal. Transducer cleaned of oil film, aimed bottom down, not tilted, tight in bracket.
4. Abandon auto sensitivity. Run it to 100%. You can always back off later if there’s too much junk on screen.
5. Ping rate 100% unless operating two sonars at once.
6. Boat speed barely moving up to fast trolling speed. In the old paper chart days it was a no-brainer to adjust chart speed to boat speed. It’s a little harder to learn now. In shallow water less than 25 feet you can run grids faster searching for fish. A scenario for you in one place might be 5 mph and medium chart speed. In deeper water slow the chart speed and drop back to lower mph. Give echoes time to return. If stopped over fish any moving fish make growing lines. If they are suspended move the boat a little to set up a typical arch display. You just need to bump the trolling motor to get a shot, like snapping a photo hitting the shutter once. Once you get a signal it will draw on the right edge of the screen and that’s all you need to watch if wishing to remain still and in stealth mode. The idea is to play with settings and speeds until you discover the best setup for the water you are in.
7. ZOOM. I rarely see anyone use the Zoom feature. It’s VERY important. The most common error is leaving a sonar set to always display all the depth range, say from 0-100 in 100’ of water. Mostly empty water column is displayed. As soon as the unit picks up a target depth range, manually zoom in to the active target depth, ignoring empty water above. You only want to view from bottom to target and slightly above target. That magnifies the images so you can pick out fish arches or more likely “slivers”, more like bananas on end or fingernail clippings.
8. Keep in mind the lessons in the document. Rounded arches are closer to center of cone and high contrast images are closer, echoing stronger signals. Faint arches sometimes appear as half arches, and those are sometimes almost standing on end, more so in the outer cone range.
If you have a problem in any of those steps we can get into detail on them. I hope that works without having to solve problems like noise.
Jim
Odds are your sonar has been mostly a bottom finder. Most of us just turned it on and take whatever it seems willing to tell us. The manual was boring and didn’t seem to connect much to real life scenarios. The demo mode always has nice fish arches and cool structure, but never on my screen. If that’s you, read on. I want to try making sonar easy toward better fishing. I highly recommend visiting the following web site for some basic information. It’s a great introduction to the subject.
http://webpages.charter.net/abshire5078/Chart tutorial.doc
Now that you’ve learned so much already, let’s think through the tool we’re trying to use. I have a 10-cell flashlight that shines a powerful small light beam surrounded by a floodlight. The center spot is really bright. The floodlight tapers off the farther from center it shines. Pointing that light down into the lake will make a cone of light shaped like a cone of sound broadcast from a sonar transducer. A small area of lake bottom would be illuminated brightly, the outer edges of light dissolving. The sound from a transducer is most powerful directly under it. The cone of a 20 degree transducer covers an area of lake bottom about 1/3 its depth, so in 100 feet the cone covers an area roughly 30 feet in diameter. But the real power is in a smaller center spot about 10 feet wide, everything outside that center in the fringe. The entire cone is like a stack of cones, the inner cone the strongest, each cone farther away from the cone axis a little weaker. It’s important to bring all that together to remember the following conclusions when using a sonar fish finder. Whatever is directly below a transducer will reflect back a strong echo. The deeper it is the longer it takes for the echo to return. Whatever is in the center cone will be reflected back stronger and sooner than anything outside that center strongest cone. Maybe now you can understand why a fish 5 feet off to the side of the cone axis and only 5 feet deep can return less of a signal as one 40 feet down directly under the transducer. The closer the stronger, but with loss of strength with increased angle away from the cone axis. That explains why you can pass directly over a large shallow fish that won’t show on the screen. It was too far out in the fringe area. At 5 feet depth the cone couldn’t be over 2 feet in diameter, so you would have to be right on that fish to display it. Yet, a school of bass is easily displayed 80 feet down.
Sonar readily "sees" the air bladder in a fish as easily as air bubbles floating up from bottom show up on screen, but also can detects their scales and fins to a lesser degree. The flesh of a fish is too close to the refractive index of water for it to distinguish the majority of a fish’s bulk. Some species have large air bladders so their arch is more pronounced than others. The closer the transducer gets to the air bladder the thicker the arch display.
By the way, one way to diagnose some fish species on sonar is to note how quickly it can swim up a great distance. A lake trout can do that easily because of a duct that regulates it's bladder. A walleye, however, must take time to burp air out to swim up quickly, the reason you should never horse a walleye from deep to shallow if you intend to release it. Let it burp its way up and there will be much less lactic acid and other gas bubble buildup in its bloodstream, and much more likely to survive to be released or stored in a livewell. Find out what your favorite fish species' air bladder characteristics are to better manage finding and handling them.
I read back through the document and decided to clarify a point or two. When a signal first appears on the right side of the screen, keep in mind it contains all echoes in a 360 degree range around the transducer. Most of what you see is going to be toward the edges of the cone, including the best signal from directly below the transducer. That's why a fish appearing on the screen probably isn't directly beneath the boat, but it appears that way. That's why it's important to compare round topped arches to sharp bent arches. It pays to study those pictures to learn the two arch shapes.
Another point is not to be discouraged over the emphasis on a color display. For obvious reasons that's much better than grayscale. I know. I've used grayscale many years and now color, and won't consider going back, but I could get along with grayscale just fine if fishing out of your boat using that display. We’re going to get into color later in another chapter. The document information applies to all display types. You can interpret the colors as variations of gray on your grayscale display. What shows up in color would appear as simply lighter or darker on grayscale. The stronger the echo, the stronger the colors. If you use grayscale you'll just have to spend more time examining the display. This also would apply to portable units hanging off a dock or tossed out from a shore. The basic principles are all the same regardless.
The display in the document is high resolution. Your unit might not be able to match that, showing blocks of images. That's a definite handicap. Might as well say that, it's fact. Do your best to come up with a 480 X 480 pixel display or better. It's the best place to put your hard earned money, above power, above screen size, or any other sonar feature including color. I'd rather have a 3" wide screen at high resolution than a 10" screen with 280 X 280 pixels. It would be no different than choosing a 40” screen TV with a very poor grainy picture over a 14” screen with excellent quality images.
To see fish arches:
1. Turn off Fish ID. The sooner you give that up the more you will get from sonar. With ID turned on you will be targeting debris galore and occasionally discover some fish.
2. Minimum noise on sonar screen. Not excess dots and meaningless lines all over. Remove all sources of electrical interference.
3. Hot battery for strong signal. Transducer cleaned of oil film, aimed bottom down, not tilted, tight in bracket.
4. Abandon auto sensitivity. Run it to 100%. You can always back off later if there’s too much junk on screen.
5. Ping rate 100% unless operating two sonars at once.
6. Boat speed barely moving up to fast trolling speed. In the old paper chart days it was a no-brainer to adjust chart speed to boat speed. It’s a little harder to learn now. In shallow water less than 25 feet you can run grids faster searching for fish. A scenario for you in one place might be 5 mph and medium chart speed. In deeper water slow the chart speed and drop back to lower mph. Give echoes time to return. If stopped over fish any moving fish make growing lines. If they are suspended move the boat a little to set up a typical arch display. You just need to bump the trolling motor to get a shot, like snapping a photo hitting the shutter once. Once you get a signal it will draw on the right edge of the screen and that’s all you need to watch if wishing to remain still and in stealth mode. The idea is to play with settings and speeds until you discover the best setup for the water you are in.
7. ZOOM. I rarely see anyone use the Zoom feature. It’s VERY important. The most common error is leaving a sonar set to always display all the depth range, say from 0-100 in 100’ of water. Mostly empty water column is displayed. As soon as the unit picks up a target depth range, manually zoom in to the active target depth, ignoring empty water above. You only want to view from bottom to target and slightly above target. That magnifies the images so you can pick out fish arches or more likely “slivers”, more like bananas on end or fingernail clippings.
8. Keep in mind the lessons in the document. Rounded arches are closer to center of cone and high contrast images are closer, echoing stronger signals. Faint arches sometimes appear as half arches, and those are sometimes almost standing on end, more so in the outer cone range.
If you have a problem in any of those steps we can get into detail on them. I hope that works without having to solve problems like noise.
Jim
There's about a dozen major functions to fiddle with, and once you get some images identified correctly, you can read on your own. Then you would explore the many minor functions that make it all the sweeter.
