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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
 

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Discussion Starter #2
Well, just like sonar sees fish air bladders first, it sees air bubbles floating up from bottom. They appear like a fish swimming up, but their graphed line is too straight. A fish won't make such a perfect slanted line. If it's straight as an arrow from lower left to upper right all the way up at a sharp vertical angle >60 degrees, it's usually a gas bubble. A bass' line will break here and there, make more of a softer 45 degree angle or less. That's all based on high sonar chart speed. Slower chart speed sharpens the angles to more vertical. That's one reason I use fast chart speed, to easily recognize gas from fish. The other is I want a fast update on when a target is closest to the transducer, or whether it's moving away. I want to know whether I'm spooking them when I arrive, which if they are spooking I will only have a last parting shot at them leaving the outer cone range. I also want the lines of moving bass flattened out so I can evaluate better how bass are relating to a lure inside the cone. I like to watch the lure make it's line, and determine whether bass make lines paralleling or intersecting my lure's line. A slow chart compacts the lines too much. That information helps me adjust lure speed, depth, etc. If I interpret the screen to say bass approach but break away, there's something wrong with the lure- they don't like it. If I didn't see that happen I might just assume there were no feeding bas in the area. But if there are feeding bass, by the fact they are following my lure, changing lure presentation style or tying on another one might catch a bass instead of motoring away.

Using sonar to find bottom and whatever else you can't tell what it is?

I don't use a sonar mostly as a "fish finder" or bottom finder. I pay a lot more attention to a small school of shad than to fish arches. In order of priority I look for structure, then baitfish, then fish arches. The idea is to first locate "different" where bass are attracted to, any feature bass like to hang around, like a ledge, hump, stump, boulder. I watch for signs of things bass eat. If I see those then I know bass are not far away and will focus on fish arches that are sometimes very hard to recognize. If I'm still over a spot and a bass moves I'll see it make a line on the screen and know its depth, and whether its swimming up, down, or horizontally then decide on the best bait presentation.

Study the tutorial to always recognize easy to see structure and balls of baitfish and you'll be well on your way to locating fish more efficiently than looking for fish on the screen.

I drop shot often, so let it down right at the trolling motor. As long as the rig stays in the cone it will make a line going down on the graph. When it stops the line levels out. Any fish coming around the bait make their own lines, horizontal if stopped, or making a zig zagged line if moving, so I can tell how the bass is relating to the bait. If I'm stopped still a still fish shows as an arch. If the arch is close and turns into a line that stays on the graph, I assume its going for the bait or at least investigating. If the bait doesn't interest the fish enough to bite it I change to something that might get a reaction bite, like a spinnerbait, jig, or spoon. Those show up even better on the graph.

Almost any movement of either boat (over maybe 1 mph) or fish destroys the arch image and replaces it with a line if the fish is moving, an indistinct blotch if the boat is moving. Usually, when the boat is travelling a few miles an hour, any suspended fish appear as inverted slivers, the front or back half of an arch, very difficult to distinguish from debris, branches, etc.. If the sensitivity is high enough and you don't have any screen clutter (from electrical noise or lots of suspended junk), it's possible all fish would make horizontal lines though not moving at all. But in fact no fish remains perfectly suspended, so the slightest movement makes at least a very thin horizontal line or row of dots. But if the screen is full of dots from debris or baitfish, you won't see a row of dots.

The arch is a peculiar image that depends on very precise sending and receiving of a sound pulse. It takes "just right" sonar conditions to see a good arch. The more still the boat, the better the imagery. That's why it's usually a waste of time motoring around looking for fish arches. It's better to look for baitfish balls or habitat. You could be passing over hundreds of bass and see nothing but what appears to be clutter. It's best to stop dead still then look. The streaking is a dead giveaway. Arches can be tree branches with some algae clumps, so I try to zoom in on that and look for the yellow bladder dot in the middle of the arch.

Take another look at page 17 in the tutotial to see a shot made by a drifting boat that caught one arch really shallow right under the transducer, and lines of active feeding fish near bottom. The closer a fish is to the center of the cone and closer to the boat, the better the arch display.

When looking over an interesting spot using sonar and you see the little "fingernail clipping" shaped objects around structure (probably fish), circle it slowly rather than run straight grids as when locating any fish at all. If you will circle around you can better picture the layout of the structure. Running a grid search at that stage of the hunt isn't productive for me since it's too hard to piece the parts together in my mind. By the time I turn back for pass #2 I can't tell where I first saw the end of a ledge, for instance. Circling keeps the structure on screen but changing so as to give me an idea which way a ledge runs. After a circle or two I can decide on the best fishing angle and set a waypoint or toss out a marker, then come back to that point to begin fishing the ledge intelligently.

So now maybe you have the whole picture. Run grids until you come across something interesting, then stop and circle around it for a closer view, zooming in on the depth of activity. Get a "picture" how the terrain is laid out and plan where to hold the boat.

Have you ever wished you could replay a view on your sonar to nail down a hot spot you got blown away from in high wind? I passed over a school of baitfish that seemed to be in the same spot in deep water, hovering around a lone group of submerged trees, not noticing that until the view was almost off the screen. I did it again in apparently the same spot the next day, and missed setting a waypoint again. I did notice trees on a lone hump, one of 3 in the area, but all different in size and height and tree/stump arrangement. I suspected that was a permanent resting place for those shad. I retraced the GPS trail but couldn’t get back on the exact spot. I needed to see what features came together that would give me a clue which way to move the boat a few feet alongside the trail, east or west along the N-S path I took. If I had been recording a sonar log I could have replayed the scenes in Simulator Mode while out there, then be able to recognize the right hump, then focus on locating the school on it. If you have the sonar feature, here’s how to do it with a Lowrance LMS332C, with similar steps on other units. With the sonar page displayed press MENU, then scroll down to Log Sonar Chart Data. Press ENT. If you accept the default options, press ENT to begin recording whatever is displayed on the screen. A MMC or SD memory card must already be in the card slot. You can record about 11 hours of sonar on a 128 MB card, 45 hours on a 512 MB card (0.9 hours per MB). When you get home you can view the whole trip on a computer using the free downloaded Sonar Viewer program, requiring a card reader to read the memory card containing the log. It’s a great way to learn more about the lake, as when fishing it’s not practical to watch the sonar constantly, so you miss some really interesting details like a school of bass suspending in a creek bottom while you were focusing on casting 150 feet the wrong direction. You can review a GPS trail automatically recorded to help figure out where the sonar view was located. Just knowing a school of large fish was suspended in a creek bottom at 25 feet depth is valuable knowledge, especially during a tournament. That could be a factor is finding a pattern that might work the next day. I’ve used the feature to run grids over a target area every 50 feet, getting a great profile of an entire creek mouth. That will paint out distribution patterns of structure, cover, and fish.

Jim
 

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Discussion Starter #3
Ya'll add your tips, or feel free to ask questions.

Jim
 

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Wow, I think I may of responded to the wrong thread earlier .

This is giving me alot to think about for when I do make the plunge and get one.

I appreciate all your time and effort in this Jim . Trust me, it isnt gong to waist.
 

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Discussion Starter #5
I've taught partners to use a GPS sounder in just a few trips, well enough for them to use the console unit from the rear deck, and use it as well as I can. There really isn't all that much to learn, about like using a VCR remote. Ugh, that might scare some folks off :eek: 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.

Jim
 

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I'd like to add my $0.02. I pride my self as being an above average shallow water guru, a trick i have been useing for awhile is to turn off my electronics when i'm 2 feet or less as it produces alot of unwanted sound. The unit is really not that much help in water that deep any way. peace out, Drew
 

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Discussion Starter #9
I've been letting this thread rest while folks find it/absorb that much, before going on. It's a favorite subject for me. I love troubleshooting GPS & Sonar problems, being trained far more than needed by Uncle Sam, attending every course available from 1995 until about 2004. A private company started up in town that wants to handle that technology for us. Well, that ended my own training and teaching government users.

So, I've enjoyed passing on the technology the past ten years, and am very active all over the internet doing that.

My aim is for nobody that wants to learn something about their equipment needs to go without or have difficulty finding answers and tips.

Glad to see some interest here :D

Jim
 

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I have a question. From what you are saying, the sonar actually picks up stronger signals directly under the transducer, and weaker at the edges. I have seen transducers that have a 60 degree cone, and some are 60/20. I have been considering buying one with the option of the 20deg. cone. Would this really be worth the money invested? I recently bought an Eagle 320C, which seems to be plenty for my boat. I guess I should look for an adapter or new transducer for that, if it really makes a difference. Also, I read in Don Iovino's book that the hooks for fish that are off to the side are recognizable because the hook is elongated to the side the fish is on. Basically, if the fish is to the right of the cone, the right side of the hook will be longer. These are extremely valuable tips for those of us who consistently set our boats up in 20+ foot of water.
 

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The fish hook trick is standard operating prcedure with about all of todays units. a solid dark fish or hook indicates the fish is in the center of the cone.
 

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Fish hooks never match the depth indicated unless directly under the transducer. In reality the sonar is only telling you how far away from the transducer a fish hook is in terms of depth. If the hook isn't equal sided, tails equal on each side of the center, then the fish is below you and if it appears to be 12' down it is. But if the same fish is swimming horizontally it will register deeper and deeper depth as though diving, because the length from the transducer is getting longer. That's why it's important to note which tail of the hook is longest, indicating which side of the boat it is and therefore direction of travel if it started out as a balanced fish hook.

Fish near the edge of the sound cone will appear as fingernail slices, not hooks, since they are in the "line of view" the shortest amount of time, getting scanned maybe once in a single reflected ping.

Hard to find for bass boats and compatible with our style electronics, a 60 degree cone is at it's best in shallow water and for boats on the go, "seeing" farther ahead. Large commercial ships use wider angles than we do. The 20 degree gives us the close-up precision scan we need, but we sacrifice area of bottom viewed. A 20 degree transducer only sees a circle of bottom 1/3 of depth to it. A wider 35-45 degree cone is delivered with a 50 khz transducer, but the target separation is lousy. That's the better choice for very deep water and salt water since sound is absorbed more there, the higher frequencies like 200 khz being absorbed more than lower frequencies like 50 khz.

Jim
 

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Jim, I currently have a sonar unit mounted on the console and just got another for Christmas which I intend to mount on the bow.  Should I mount the transducer on the trolling motor or elsewhere.  The unit I have on the console is a Humminbird 565 and the new unit is a 535.  The first transducer is mounted on the outside of the transom.  Also, if you have two units running at the same time, what ping rate do you need to use or is it best to just run one unit at a time?   ??? ??? ???
 

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Discussion Starter #14
You can get the trolling motor mount kit but it's cheaper to just use an electric clothes dryer exhaust band. Most of the tducer brackets have the slot for it.

I wouldn't want to try attaching a bow tducer to the hull. Stick it on the trolling motor. When you are at the console it's likely the trolling motor is pulled up and nobody is on the bow anyway.

I run both at once most of the time. The console unit is constantly logging sonar on a MMC card so I can study what I missed while fishing and not paying attention to the sonar screen.

I always run the console at 100% ping at the console since that's needed for high speed sounding, and keep the bow unit at below 50%.

You can also aim the aft tducer a few degrees farther aft without messing up accuracy. That way even in deep water the sound cones never touch. Under 10 feet you only have a viewing spot under a tducer measuring about 3 feet wide, so you might as well turn both off. Bass can easily hear the pinging and associate that with the outline of your boat, then scram.

Jim
 

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I have a 14 ft. jonboat, as I think you know. My transducer is mounted on my trolling motor. The problem with this is that my trolling motor is on an angle to the water, as my jonboat is built bow up. (I hope you can understand) I really dont want to drill any holes, but I need a better mount for my transducer. As it is, the thing can vary 2-5 feet in water depth just by a change in the direction the trolling motor is facing.
 

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I think I get it, like the gator trolling motors that slant way behind the transom, sort of lying flat?

Sounds to me like you have no alternative but to mount a separate braket holding just the tducer that can be dropped in the water with or without trolling motor. You could probably make a simple hinged arm.

You could also mount the second ducer on the transom, but then run one or the other.

Jim
 

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I was also thinking about using epoxy to permanently attach the transducer to the bottom of the boat. (Hopefully below the waterline, if I do it right :p ) But it seems that I read somewhere that the aluminum would cause interference in the signal. Is this true, if the thing is attached outside the boat?
 

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Unless you have a Vexilar AlumaDucer that is supposed to shoot through an aluminum hull, you need a skimmer designed to attach outside the boat in the water. If you can find a flat place in the bow that allows the ducer to shoot straight down, that'll work fine without interference. Be sure to aim the round nose forward. You'd have to figure a way to attach the cable to the hull so nothing can slide between the cable and hull, rippingthe ducer free and maybe severing the cable. The problem with that setup is beaching it on a rock. Gone. Just having it on hard ground and stepping on the bow could crack it.

To keep the bow deck clear another idea I have is to mount a pivoting bar or board on the side of the bow. Put a hook on one end to clamp the thing level with the gunwale while boating around, then unhook it, swing the ducer end into the water, hook it in place somehow. That way it's completely out of the way, and when you see that bar standing you are reminded to stow it away before cranking up. Rednecky enough for ya? ;D

Jim
 
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