I had posted ALL of this info in the past....but had a hard time finding it....so here it is in ONE chunk. I hope some of you find it useful!
Depth / fishfinders are a God-send to some folks…yet others struggle with the electronics and operational aspects. I have accumulated some info over the years...tips and links here for those of you looking for help. For those of you that have some good info to offer, please don’t hesitate to leave it here to help out our fish-brothers and sisters. If you have had any different experiences that what I have posted here, PLEASE feel free to post them too.
Eagle product "emulators"
For Raymarine, you have to create an account...
And here's Si-Tex FAQ's / Q & A http://www.si-tex.com/html/faq_s.html
Fish Finder / GPS manufacturers
http://www.find-fish.com/ (Sells and supports ALL major brands)
http://www.humminbird.com/home.asp?ID=2 (main website)
http://www.lowrance.com/ (At the top of the page, click on the "Support" tab)
http://www.garmin.com/support/ (Tech Support)
http://www.eaglegps.com/Support/default.htm (Tech Support)
http://www.raymarine.com/raymarine/default.asp?site=1§ion=3 (Tech Support)
http://www.norcrossmarine.com/default (Hawkeye finders)
Here’s a website dedicated to fishfinders…
Fish Finder Reviews
Some Buying Tips
The Marine Electronics Journal
Learning to Use Fishfinders
Time on the water is your best teacher. If it is crystal clear and you can see the bottom, this will show you a lot also, and you can relate what the screen shows you versus what you can physically see. Another good idea can be to use a camera.
You’d probably be amazed at the number of folks that have spent a lot of time fishing for stupid rocks that they thought were fish.
Use the unit in automatic mode till you get the feel of how the unit performs. Once you feel comfortable with it, then switch it to manual mode, where you can do so much more with the unit. Also take the time to sit down and read the manual…there is a wealth of information in that book. Many folks still use older units, and during their time, they were the best of what was available. But they really don't compare to the newer units of today. The newer ones have better memory, better resolution and so much more cool stuff, many more features integrated into them. The night vision mode is very easy on the eyes, and the mapping units are amazing and very accurate.
Probably the biggest thing is trusting what the unit is telling you. Get rid of the fishy symbols as the unit is telling you what it thinks it sees, and it takes a lot of power to create those symbols.
Hard bottoms will show a thick grayline as the signal goes down bounces off and comes back fast, and soft bottoms will show a thin grayline as the signal gets lost in the mud and takes it a while to get back to the depth finder. Run your tracking speed wide open on the unit…the more information you can receive the better. Everything on the right side of the screen is the newest information. If the unit has a built-in flasher mode, you should consider having that on also, as it will show you real-time information plus what is directly under the boat.
You can set the sensitivity by going into approx. 20 foot of water and dropping a 1/4oz jig below the transducer. Let it hit the bottom, pick it up and drop it back down again. You should be able to bump up the sensitivity till you can see that jig go up and down on the screen, and that will get you real close to the ballpark of having the correct setting. In the automatic mode, it may filter it out or miss it totally, so manual mode would be the choice for this set-up.
Each and every time you go to launch the boat check the position of the transducer on the back, these things get bumped up or down during transportation, so each trip just make sure it is in the correct position as you undo the straps. Also, wipe it down, because dust or mud will collect and it is amazing what kind of readings you get with dust or mud on the eyes of a unit.
Sensitivity settings should be somewhere in the 65%-85% range depending on the units power. The more power, the less you have to crank up the sensitivity. The units work very well in 10- 50 foot of water…actually, the deeper the water the better separation between fish and structure. Bottom feeders like Flatheads will blend in with the bottom structure, so sometimes it is hard to pick them up, but there are tricks to the trade.
Remember also, and this is something many anglers don't understand about their electronics, is that the depth shown on your screen is the distance from the transducer to the shallowest point in the area displayed. If the bottom drops off in that area you will have a "dead spot", where there may be fish that you don't see. When you’re moving parallel along breaklines this can cause to you miss seeing many fish. You can see any fish that are on such structure by moving perpendicularly to the breakline, letting the edge of the cone travel up the slope of the contour, then moving out and repeating the perpendicular approach, stitching the breakline, in-and-out, in-and-out, etc.. Get rid of the fish pictures.
Manufacturers of fishing electronics try to make units that can be bought, off-the-shelf, installed and used by the average angler, with little or no technical knowledge, and deliver as much information as possible. There is no way however, for these units to differentiate between air bubbles, leaves or other suspended objects, or a layer where water density changes due to stratification, and fish. They will show you a fish picture whenever the signal bounces off of anything between the transducer and the bottom. Using your unit in manual mode, properly adjusted for water depths and conditions, will give you information that you can interpret, after gaining some experience, to give you a better idea of what is actually down there.
Sensitivity is one of the things that confuses some anglers. Many think that by increasing the sensitivity they will be able to see more and better. This isn't always the case. Take saugeye for an example; they are a bottom relating fish, and often lie so tight to the bottom that they are very hard to see. With the sensitivity turned up you will be able to see more and smaller baitfish, the dense water layer at the thermocline, etc…, but the strength of the signal will cause a fish that is on the bottom to "blend" with the bottom, showing merely a small bump, with no separation or internal Grayline. By decreasing your sensitivity setting you will lose the ability to see smaller objects like small baitfish but you will be more likely to see a separation of fish from the bottom. Using your Zoom function also helps in seeing fish that are glued to the bottom. When in the Zoom mode each pixel on your readout screen represents less of the water column, therefore providing more detail and better separation.
Tips to Remember
1. Do a physical check of the installation. It's important to look for cracks, chafing or breaks in the line since these problems can cause intermittent performance. When conducting your evaluation, pay close attention to the transducer cable.
2. Check a transom-mounted transducer for placement. It should be aligned with the water when it's in the down position. Also check that the kick-up mechanism is operating properly.
3. Check the inline fuse container. Approximately 60 percent of performance problems in older units can be traced to a buildup of oxidation where the fuse ends make contact with the container, says Luke Morris of Lowrance. If buildup exists, use a piece of Scotch Brite pad to scrub off the oxidation.
4. When prepping your boat for spring with a fresh coat of bottom paint, be sure to avoid covering your through-hull transducer. Special coatings for transducers are available.
5. Remember that the screen images you see are history. The only real-time "picture" is on the far right side of the screen, and on the A-scope, if your unit is equipped with that feature.
6. Re-read the manual while using the simulator. There is a ton of information that you may have overlooked last year or don't remember. When you're finished, be sure to deactivate the simulator.
7. If you want to buy a new fishfinder this season, don't be confused by the output power ratings. There are two specifications: Root Mean Square (RMS) and Peak-to-Peak (PtP). One is not more powerful than the other; it's just the way power ratings are measured and reported. RMS is a lower figure than PtP by a factor of eight. To get RMS, divide PtP by eight; to get PtP, multiply RMS by eight. It seems that freshwater fishermen understand PtP, while saltwater anglers deal in RMS.
8. When selecting a working frequency in a dual-frequency model, remember that 200 kHz is designed for shallower water to 600 feet, while 50 kHz penetrates deeper, especially in saltwater. Higher frequencies provide better resolution and target separation, while the lower range can "see" fish in deeper waters, although resolution and target separation suffer somewhat.
9. When "reading" the screen, remember that all targets are not located directly under the transducer at the depth specified on the display. A fish reported at 12 feet could actually be at only nine feet. It all depends on the fish's position within the 360-degree cone of energy generated by the transducer. In this case, if the fish is directly under the transducer, it's probably 12 feet down. If the fish is at the outer edge of the cone, it could be in nine feet of water.
Here's some help to one of our Members given by ouachitabassangler
Posted by bb July 05, 2005, 01:21 PM
Depth Finder Problems
I just had the 3rd depth finder in my boat go out. (Lowrance X-48 I think)They work for a little while and then they won't come on or they work intermittently.
There doesn't seem to be any power problems. There are no bare wires touching each other that I can find. The boat is 100% fiberglass/composite. Any ideas?
Posted by ouachitabassangler July 05, 2005, 02:00 PM
One thing to look at is to test the battery for adequate voltage. My Lowrance 332C quit on me on the lake, going off without notice, acting erratically. Turned out its battery was only putting out 10.6 volts, having one bad cell.
My next door neighbor came over with a similar problem. He had been replacing Lowrance sonars right & left, but was not changing out the power wiring since all the Lowrances use the same plugs on the NEMA cable standard. After going up the chain to a $2,600 unit that wouldn't work, he decided to get advice. It turned out the wiring he was "sure" was good wasn't, because when we replaced it with a completely new transducer and power wiring completely apart from other boat wires, the new unit worked perfectly.
Always put the new transducer on and ALWAYS run a good power wire from preferably a dedicated battery. I run boat lights and all electronics off one deep cycle battery that can be switched to the trolling motor. Once you get a k n o w n good power wire run through some plastic shielding (using braided wire for flexibility), you can periodically pull new wire through using the old as a pull guide.
Boats vibrate when run over water and over the road, weakening electrical connections. Rather than try to find all the bad spots, I save time replacing all of it.
Posted by bb July 06, 2005, 05:00 AM
Thanks for the info. Should I replace the transducer as well when I replace the wiring?
Posted by ouachitabassangler July 07, 2005, 07:50 AM
Whenever I change a sonar unit I always use the transducer that comes with it. They do eventually burn out, but before that begin sending bad signals. If there's a little crimp in the transducer cable, that alone can easily mess the sonar up. If not enough good signal is carried, the sonar will mess up in various ways, mostly showing too much noise on screen, or shut it down as though not even hooked up to a transducer.
Posted by Ronald powell July 20, 2005, 09:00 PM
CHECK YOUR GROUNDING A COMMON PROBLEM IS LOOSE GROUND CUASING SHORT IN DISPLAY
The next article was found at....
Finding or selecting the right fish finder can be a frustrating job! We are here to help give you some coaching that we hope will make the process easier for you.
As with most electronic items you will notice that technology has helped to create an environment where you get so much more today than years ago for less dollars.
The first thing to consider when purchasing or selecting a fish finder is what general price range do you want to stay with-in. Stick with-in your budget and see what options you have to still get all the necessary components included in your selection. Some models come either in monochrome or color. Color is nice but is it necessary?
How you plan to use your fish finder is extremely important! If you plan to go on a fishing trip and primarily use your fish finder in small row boats then you really need a portable fish finder or a standard fish finder that has a portable package to make it portable when you want it to be portable. If you are like me in that you enjoy your fishing trips but also want a permanent fish finder in your main boat then I would suggest that you consider one portable stand alone unit for your little row boat applications and then a permanent additional fish finder for your main boat.
In each of the different brands that I carry (Eagle, Lowrance, Humminbird and Garmin) I have the portable fish finders at the beginning of the product page. Notice whether the portable fish finder would sit on the seat of the boat in such a way that it would be readily visible for you to glance at. Your seat configuration of your small boat will help you decide how large of a unit you would want. I prefer to have my fish finder on the seat right in front of me as opposed to next to me on the same seat.
The power consumed in the portables will relate to the signal strength of the sonar and it will also affect the life of the batteries. Some use lantern style batteries and others have smaller D or A type batteries. To me the battery selection is not critical because once I get into my fishing position I will turn my fish finder off until I get ready to move again or start trolling.
Lets talk about monochrome and color again. Color is very nice if the dollars do not stand in your way. For years I have used a monochrome display and I have done just fine but as technology advances the price for color has become affordable and it would be like asking me if I want to watch black and white TV. I still get all the right messages with monchrome but color is so much more fun. Remember as I stated above STAY WITH-IN YOUR BUDGET!!!
Screen size just as in TV's typically means that the wider the screen and thus the viewing area the more costly the fish finder will be. The number of pixels that the unit has will directly affect the sharpness and clarity of the display. The more pixels that you have the sharper the image will be.
You have probably noticed that some fish finders are advertized touting that they are either single frequency or dual frequency. The transponder is either a dual frequency transponder with a 50KHZ and a 200KHZ Sonar or a single frequency transponder with a 200KHZ Sonar. The dual frequency transponder units typically cost more. The dual frequency units are great if you have the needs for the dual frequency unit which is that you are fishing in VERY VERY DEEP WATER or in SALT WATER. The 50KHZ transponder will penetrate the salt water better than the 200KHZ transponder and the 50KHZ transponder will also give a better signal in the deep water (over 200' deep). All that being said if you fish in inland lakes that are fresh water and under 200 feet deep you will most likely do well with the more INEXPENSIVE single frequency 200KHZ unit.
Fish finders now are also available with GPS, WAAS and mapping options. Depending on what and where you are going will determine whether you would want these options. When I am fishing in Canada and I am not familiar with the lake a GPS hand held does the trick for me. It maps out where my way
points are so that I can get back to camp at night with out getting lost. It also marks my hot fishing locations so I can come back later to the very same spot. If you are doing some serious boating around complicated structures and islands that become very confusing then the GPS, WAAS and mapping options are very beneficial to have.
If you want to learn what Sonar is and how Lowrance Electronics uses Sonar in its products, you are in the right place.
The word "Sonar" is an abbreviation for "SOund, NAvigation, and Ranging." It was developed as a means of tracking enemy submarines during World War II. A sonar consists of a transmitter, transducer, receiver and display.
In the simplest terms, an electrical impulse from a transmitter is converted into a sound wave by the transducer and sent into the water. When this wave strikes an object, it bounces back. This bounce back hits the transducer, which converts it back into an electric signal. This signal is amplified by the receiver and sent to the display. This process repeats itself many times per second.
There are four facets to a good sonar unit:
1. High power transmitter.
2. Efficient transducer.
3. Sensitive receiver.
4. High resolution and high contrast display.
High transmitter power increases the probability that you will get a return echo in deep water or poor water conditions. It also lets you see fine detail, such as bait fish and structure.
The transducer must not only be able to withstand the high power from the transmitter, but it also has to convert the electrical power into sound energy with little loss in signal strength. At the other extreme, it has to be able to detect the smallest of echoes returning from deep water or tiny bait fish.
The receiver also has an extremely wide range of signals it has to deal with. It must dampen the extremely high transmit signal and amplify the small signals returning from the transducer. It also has to separate targets that are close together into distinct, separate impulses for the display.
The display must have high resolution (vertical pixels) and good contrast to be able to show all of the detail crisply and clearly. This allows fish arches and fine detail to be shown.
Most Lowrance sonar units today operate at 192 or 200 kHz (kilohertz), with a few using 50 kHz. There are advantages to each frequency, but for almost all freshwater applications and most saltwater applications, 192 or 200 kHz is the best choice. It gives the best detail, works best in shallow water and at speed, and typically shows less "noise" and undesired echoes. Target definition is also better with these higher frequencies. This is the ability to display two fish as two separate echoes instead of one "blob" on the screen.
There are some applications where a 50 kHz frequency is best. Typically, a 50 kHz sonar (under the same conditions and power) can penetrate water to deeper depths than higher frequencies. This is due to water's natural ability to absorb sound waves. The rate of absorption is greater for higher frequency sound than it is for lower frequencies. Therefore, you'll generally find 50 kHz used in deeper saltwater applications. Also, 50 kHz transducers typically have wider coverage angles than 192 or 200 kHz transducers. This characteristic makes them useful in tracking multiple downriggers. Thus, even when these downriggers are in relatively shallow depths, 50 kHz is preferred by many fishermen.
In summary, the differences between these frequencies are:
192 or 200 kHz:
Narrow cone angle.
Better definition and target separation.
Less noise susceptibility.
Wide cone angle.
Less definition and target separation.
More noise susceptibility.
The transducer is the sonar unit's "antenna." It converts electric energy from the transmitter to high frequency sound. The sound wave from the transducer travels through the water and bounces back from any object in the water. When the returning echo strikes the transducer, it converts the sound back into electrical energy which is sent to the sonar unit's receiver. The frequency of the transducer must match the sonar unit's frequency. In other words, you can't use a 50 kHz transducer or even a 200 kHz transducer on a sonar unit designed for 192 kHz! The transducer must be able to withstand high transmitter power impulses, converting as much of the impulse into sound energy as possible. At the same time, it must be sensitive enough to receive the smallest of echoes. All of this has to take place at the proper frequency and reject echoes at other frequencies. In other words, the transducer must be very efficient.
Crystal The active element in a transducer is a man-made crystal (lead zirconate or barium titanate). To make these crystals the chemicals are mixed, then poured into molds. These molds are then placed in an oven which "fires" the chemicals into the hardened crystals. Once they've cooled, a conductive coating is applied to two sides of the crystal. Wires are soldered to these coatings so the crystal can be attached to the transducer cable. The shape of the crystal determines both its frequency and cone angle. For round crystals (used by most sonar units), the thickness determines its frequency and the diameter determines the cone angle or angle of coverage (see Cone Angles section). For example at 192 kHz, a 20 degree cone angle crystal is approximately one inch in diameter, whereas an eight degree cone requires a crystal that is about two inches in diameter. That's right. The larger the crystal's diameter - the smaller the cone angle. This is the reason why a twenty degree cone transducer is much smaller than an eight degree one - at the same frequency.
Housings Transducers come in all shapes and sizes. Most transducers are made from plastic, but some thru-hull transducers are made from bronze. As shown in the previous section, frequency and cone angle determine the crystal's size. Therefore, the transducer's housing is determined by the size of the crystal inside. For more information on transducer types and their applications see The Transducer Selection Guide.
Speed and the Transducer
Cavitation is a major obstacle to achieving high speed operation. If the flow of water around the transducer is smooth, then the transducer sends and receives signals normally. However, if the flow of water is interrupted by a rough surface or sharp edges, then the water flow becomes turbulent. So much so that air becomes separated from the water in the form of bubbles. This is called "cavitation." If these air bubbles pass over the face of the transducer (the part of the housing that holds the crystal), then "noise" is shown on the sonar unit's display. You see, a transducer is meant to work in water - not air. If air bubbles pass over the transducer's face, then the signal from the transducer is reflected by the air bubbles right back into it. Since the air is so close to the transducer, these reflections are very strong. They will interfere with the weaker bottom, structure, and fish signals, making them difficult or impossible to see.
The solution to this problem is to make a transducer housing that will allow the water to flow past it without causing turbulence. However, this is difficult due to the many constraints placed upon the modern transducer. It must be small, so that it doesn't interfere with the outboard motor or its water flow. It must be easy to install on the transom so that a minimum of holes need to be drilled. It must also "kick-up" without damage if struck by another object. Again, the patented design of the HS-WS transducer is Lowrance's latest improvement in high-speed transducer technology. It combines high speed operation with easy installation and will "kick-up" if struck by an object at high speed.
The cavitation problem is not limited to the shape of the transducer housing. Many boat hulls create air bubbles that pass over the face of a transom mounted transducer. Many aluminum boats have this problem due to the hundreds of rivet heads that protrude into the water. Each rivet streams a river of air bubbles behind it when the boat is moving, especially at high speed. To fix this problem, mount the face of the transducer below the air bubbles streaming from the hull. This typically means you have to mount the transducer's bracket as far down as possible on the transom.
Transducer Cone Angles:
The transducer concentrates the sound into a beam. When a pulse of sound is transmitted from the transducer, it covers a wider area the deeper it travels. If you were to plot this on a piece of graph paper, you would find that it creates a cone shaped pattern, hence the term "cone angle." The sound is strongest along the center line or axis of the cone and gradually diminishes as you move away from the center. In order to measure the transducer's cone angle, the power is first measured at the center or axis of the cone and then compared to the power as you move away from the center. When the power drops to half (or -3db[decibels] in electronic terms), the angle from that center axis is measured. The total angle from the -3db point on one side of the axis to the -3db point on the other side of the axis is called the cone angle.
This half power point (-3db) is a standard for the electronics industry and most manufacturers measure cone angle in this way, but a few use the -10db point where the power is 1/10 of the center axis power. This gives a greater angle, as you are measuring a point further away from the center axis. Nothing is different in transducer performance; only the system of measurement has changed. For example, a transducer that has an 8 degree cone angle at -3db would have a 16 degree cone angle at -10db.
Lowrance offers transducers with a variety of cone angles.
Wide cone angles will show you more of the underwater world, at the expense of depth capability, since it spreads the transmitter's power out. Narrow cone angle transducers won't show you as much of what's around you, but will penetrate deeper than the wide cone. The narrow cone transducer concentrates the transmitter's power into a smaller area. A bottom signal on the sonar unit's display will be wider on a wide cone angle transducer than on a narrow one because you are seeing more of the bottom. The wide cone's area is much larger than the narrow cone.
High frequency (192 - 200 kHz) transducers come in either a narrow or wide cone angle. The wide cone angle should be used for most freshwater applications and the narrow cone angle should be used for all saltwater applications. Low frequency (50 kHz) sonar transducers are typically in the 30 to 45 degree range. Although a transducer is most sensitive inside its specified cone angle, you can also see echoes outside this cone; they just aren't as strong. The effective cone angle is the area within the specified cone where you can see echoes on the display. If a fish is suspended inside the transducer's cone, but the sensitivity is not turned up high enough to see it, then you have a narrow effective cone angle. You can vary the effective cone angle of the transducer by varying the receiver's sensitivity. With low sensitivity settings, the effective cone angle is narrow, showing only targets immediately beneath the transducer and a shallow bottom. Turning the sensitivity control up increases the effective cone angle, letting you see targets farther out to the sides.
Water and Bottom Conditions: The type of water you're using the sonar in affects its operation to a large degree. Sound waves travel easily in a clear freshwater environment, such as most inland lakes. In salt water however, sound is absorbed and reflected by suspended material in the water. Higher frequencies are most susceptible to this scattering of sound waves and can't penetrate salt water nearly as well as lower frequencies. Part of the problem with salt water is that it's a very dynamic environment - the oceans of the world. Wind and currents constantly mix the water. Wave action creates and mixes air bubbles into the water near the surface, which scatters the sonar signal. Micro-organisms, such as algae and plankton, scatter and absorb the sonar signal.
Minerals and salts suspended in the water do the same thing. Fresh water also has wind, currents and micro-organisms living in it that affect the sonar's signal - but not as severely as salt water.
Mud, sand and vegetation on the bottom absorb and scatter the sonar signal, reducing the strength of the return echo. Rock, shale, coral and other hard objects reflect the sonar signal easily. You can see the difference on your
sonar's screen. A soft bottom, such as mud, shows as a thin line across the screen. A hard bottom, such as rock, shows as a wide line on the sonar's screen.
Water Temperature and Thermoclines:
Water temperature has an important influence upon the activities of all fish. Fish are cold-blooded and their bodies are always the temperature of the surrounding water. During the winter, colder water slows down their metabolism. At this time, they need about a fourth as much food as they consume in the summer.
Most fish don't spawn unless the water temperature is within rather narrow limits. The surface water temperature gauge built into many of our sonar units helps identify the desired surface water spawning temperatures for various species. For example, trout can't survive in streams that get too warm. Bass and other fish eventually die out when stocked in lakes that remain too cold during the summer. While some fish have a wider temperature tolerance than others, each has a certain range within which it tries to stay. Schooling fish suspended over deep water lie at the level that provides this temperature. We assume they are the most comfortable here.
The temperature in a lake is seldom the same from the surface to the bottom. Usually there is a warm layer of water and a cooler layer. Where these layers meet is called a thermocline. The depth and thickness of the thermocline can vary with the season or time of day. In deep lakes there may be two or more thermoclines. This is important because many species of game fish like to suspend in, just above, or just below the thermocline. Many times bait fish will be above the thermocline while larger game fish will suspend in or just below it. Fortunately, this difference in temperatures can be seen on the sonar screen. The greater the temperature differential, the denser the thermocline shows on the screen.
After starting your boat, go to a protected cove and stop. Leave the engine on. You may want to take a partner along to operate the boat while you learn how to use the sonar. Press the sonar unit's ON key and idle slowly around the cove. You'll probably see a screen similar to the one to the left. The dashed line at the top of the screen represents the surface. The bottom shows in the lower part of the screen. The current water depth (33.9 feet) shows in the upper left corner of the screen. The depth range in this example is 0 to 40 feet. Since the unit is in the automatic mode, it continually adjusts the range, keeping the bottom signal on the display.
Fish-Symbol I.D.™ Every Lowrance LCG offers the convenience of our Advanced Fish-Symbol I.D.™. Activated by the press of a button, Advanced Fish Symbol I.D.™ lets your unit do the work of interpreting return sonar signals. Advanced Fish Symbol I.D.™ works in automatic mode only. If you turn it on while in manual mode, it will switch to automatic mode. Fish and other suspended targets are clearly displayed as fish-shaped symbols in four different sizes. Advanced Fish Symbol I.D.™ is designed to give a simplified, easy to interpret display of suspended targets that are assumed to be fish. After gaining experience with your sonar, you will probably turn it off much of the time so you can see all of the detailed information on fish movement, thermoclines, schools of baitfish, weed beds, bottom structure, etc.
ASP™ (Advanced Signal Processing)
Advanced Signal Processing (ASP™) is another exclusive Lowrance innovation that uses sophisticated programming and advanced digital electronics to continually monitor the effects of boat speed, water conditions and other interference sources - and automatically adjusts the sonar settings to provide the clearest picture possible. ASP™ sets the sensitivity as high as possible while keeping the screen free of "noise." It automatically balances sensitivity and noise rejection. The feature can be turned off and on and will work whether the sonar is in automatic or manual mode. With ASP™ operating behind the scenes you'll spend less time making routine sonar adjustments and more time spotting fish.
The sensitivity controls the ability of the unit to pick up echoes. A low sensitivity level excludes much of the bottom information, fish signals, and other target information. High sensitivity levels enable you to see this detail, but it can also clutter the screen with many undesirable signals. Typically, the best sensitivity level shows a good solid bottom signal with GRAYLINE® and some surface clutter. When in the automatic mode, the sensitivity is automatically adjusted to keep a solid bottom signal displayed, plus a little more. This gives the unit the capability to show fish and other detail. In automatic mode, the unit also adjusts sensitivity automatically for water conditions, depth, etc. When you adjust the sensitivity up or down, you are biasing up or down the normal setting the unit's automatic control would choose. With ASP™ enabled, the automatic mode picks the proper sensitivity level for 95% of all situations, so it is recommend to always use this normal mode first. But, for those unusual situations where it is warranted you can bias it up or down. You can also turn off the automatic sensitivity control for special uses.
To properly adjust the sensitivity while the unit is in the manual mode, first change the range to double its current setting. For example, if the range is 0 - 40 feet, change it to 0 - 80 or 0 - 100 feet. Now increase the sensitivity until a second bottom echo appears at twice the depth of the actual bottom signal. This "second echo" is caused by the echo returning from the bottom reflecting off the surface of the water, making a second trip to the bottom and returning. Since it takes twice as long for this echo to make two trips to the bottom and back, it shows at twice the depth of the actual bottom. Now change the range back to the original scale. You should see more echoes on the screen. If there is too much noise on the screen, back the sensitivity level down a step or two.
GRAYLINE® lets you distinguish between strong and weak echoes. It "paints" gray on targets that are stronger than a preset value. This allows you to tell the difference between a hard and soft bottom. For example, a soft, muddy or weedy bottom returns a weaker symbol which is shown with a narrow or no gray line. A hard bottom returns a strong signal which causes a wide gray line. If you have two signals of equal size, one with gray and the other without, then the target with gray is the stronger signal. This helps distinguish weeds from trees on the bottom or fish from structure.
GRAYLINE® is adjustable. Since GRAYLINE® shows the difference between strong and weak signals, adjusting the sensitivity may also require a different GRAYLINE® level.
You may see fish arches while trolling with the unit in a 0 - 60 foot scale, however it it much easier to see the arches when using the zoom feature. This enlarges all echoes on the screen. Turning the zoom feature on gives you a screen similar to the one at left. The range is 8 - 38 feet, a 30-foot zoom. As you can see, all targets have been enlarged, including the bottom signal. Fish arches (A & B) are much easier to detect, and important structure (C) near the bottom is magnified. This also shows small fish hanging just beneath the surface clutter (D). The above steps are all that's required to manually adjust your sonar unit for optimum fish finding capability. After you've become more familiar with your unit, you'll be able to adjust the sensitivity properly without having to look for a second echo.
Fish Arches: One of the most common questions that we receive is "How do I get fish arches to show on my screen?" It's really pretty simple to do, but it does require attention to detail, not only in the way you make the adjustments to the unit, but to the whole sonar installation. It also helps to see the Why Fish Arch section below. This explains how arches are created on your sonar's screen.
Screen Resolution The number of vertical pixels that the screen is capable of showing is called Screen Resolution. The more vertical pixels on a sonar's screen, the easier it will be for it to show fish arches. This plays an important role in a sonar unit's capability to show fish arches.
One pixel represents a larger volume of water with the unit in the 0 - 100 foot range than it does with the unit in the 0 - 10 foot range. For example, if a sonar has 100 pixels vertically, with a range of 0 - 100 feet, each pixel is equal to a depth of 12 inches. A fish would have to be pretty large to show up as an arch at this range. However, if you zoom the range to a 30-foot zoom (for example from 80 to 110 feet), each pixel is now equal to 3.6 inches. Now the same fish will probably be seen as an arch on the screen due to the zoom effect. The size of the arch depends on the size of the fish - a small fish will show as a small arch, a larger fish will make a larger arch, and so on. Using a sonar unit with a small number of vertical pixels in very shallow water, a fish directly off the bottom will appear as a straight line separate from the bottom. This is because of the limited number of dots at that depth. If you are in deep water (where the fish signal is displayed over a larger distance of boat travel), zooming the display into a 20 or 30 foot window around the bottom shows fish arches near the bottom or structure. This is because you have reduced the pixel size in a larger cone.
Chart Speed The scrolling or chart speed can also affect the type of arch displayed on the screen. The faster the chart speed, the more pixels are turned on as the fish passes through the cone. This will help display a better fish arch. (However, the chart speed can be turned up too high. This stretches the arch out. Experiment with the chart speed until you find the setting that works best for you.)
Transducer Installation If you still don't get good fish arches on the screen, it could be the transducer's mounting is incorrect. If the transducer is mounted on the transom, adjust it until its face is pointing straight down when the boat is in the water. If it is angled, the arch won't appear on the screen properly. If the arch slopes up but not down, then the front of the transducer is too high and needs to be lowered. If only the back half of the arch is printed, the nose of the transducer is angled too low and needs to be raised.
Fish Arch Review
1. Sensitivity Automatic operation with Advanced Signal Processing (ASP™) turned on should give you the proper sensitivity settings but, if necessary, the sensitivity may be increased.
2. Target Depth The depth of the fish can determine if the fish will arch on the screen. If the fish is in shallow water, the fish is not in the cone angle very long, making it difficult to show an arch. Typically, the deeper the fish, the easier it is to show an arch.
3. Boat Speed The boat's engine should be in gear at an idle or just above. Experiment with your boat to find the best throttle location for good arches. Usually, a slow trolling speed works best.
4. Chart Speed Use at least 3/4 chart speed or higher.
5. Zoom Size If you see markings that are possible fish, but they do not arch, zoom in on them. Using the zoom function lets you effectively increase the screen's resolution.
Final Notes on Fish Arches
Very small fish probably will not arch at all. Because of water conditions such as heavy surface clutter or thermoclines, the sensitivity sometimes cannot be turned up enough to get fish arches. For the best results, turn the sensitivity up as high as possible without getting too much noise on the screen. In medium to deep water, this method should work to display fish arches. A school of fish will appear as many different formations or shapes depending on how much of the school is within the transducer's cone. In shallow water, several fish close together appear like blocks that have been stacked in no apparent order. In deep water, each fish will arch according to its size.
Why Fish Arch
The reason fish show as an arch is because of the relationship between the fish and the cone angle of the transducer as the boat passes over the fish. As the leading edge of the cone strikes the fish, a display pixel is turned on. As the boat passes over the fish, the distance to the fish decreases. This turns each pixel on at a shallower depth on the display. When the center of the cone is directly over the fish, the first half of the arch is formed. This is also the shortest distance to the fish. Since the fish is closer to the boat, the signal is stronger and the arch is thicker. As the boat moves away from the fish, the distance increases and the pixels appear at progressively deeper depths until the cone passes the fish. If the fish doesn't pass directly through the center of the cone, the arch won't be as well defined. Since the fish isn't in the cone very long, there aren't as many echoes to display, and the ones that do show are weaker. This is one of the reasons it's difficult to show fish arches in shallow water. The cone angle is too narrow for the signal to arch.
Remember, there must be movement between the boat and the fish to develop an arch. Usually, this means trolling at a slow speed with the main engine. If you are anchored or stopped, fish signals won't arch. Instead, they'll show as horizontal lines as they swim in and out of the cone.
What is GPS? (Garmin tutorial)
The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS.
How it works
GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the user's exact location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map.
A GPS receiver must be locked on to the signal of at least three satellites to calculate a 2D position (latitude and longitude) and track movement. With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude). Once the user's position has been determined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time and more.
How accurate is GPS?
Today's GPS receivers are extremely accurate, thanks to their parallel multi-channel design. Garmin's 12 parallel channel receivers are quick to lock onto satellites when first turned on and they maintain strong locks, even in dense foliage or urban settings with tall buildings. Certain atmospheric factors and other sources of error can affect the accuracy of GPS receivers. Garmin® GPS receivers are accurate to within 15 meters on average.
Newer Garmin GPS receivers with WAAS (Wide Area Augmentation System) capability can improve accuracy to less than three meters on average. No additional equipment or fees are required to take advantage of WAAS. Users can also get better accuracy with Differential GPS (DGPS), which corrects GPS signals to within an average of three to five meters. The U.S. Coast Guard operates the most common DGPS correction service. This system consists of a network of towers that receive GPS signals and transmit a corrected signal by beacon transmitters. In order to get the corrected signal, users must have a differential beacon receiver and beacon antenna in addition to their GPS.
The GPS satellite system
The 24 satellites that make up the GPS space segment are orbiting the earth about 12,000 miles above us. They are constantly moving, making two complete orbits in less than 24 hours. These satellites are traveling at speeds of roughly 7,000 miles an hour.
GPS satellites are powered by solar energy. They have backup batteries onboard to keep them running in the event of a solar eclipse, when there's no solar power. Small rocket boosters on each satellite keep them flying in the correct path.
Here are some other interesting facts about the GPS satellites (also called NAVSTAR, the official U.S. Department of Defense name for GPS):
The first GPS satellite was launched in 1978. A full constellation of 24 satellites was achieved in 1994. Each satellite is built to last about 10 years.
Replacements are constantly being built and launched into orbit. A GPS satellite weighs approximately 2,000 pounds and is about 17 feet across with the solar panels extended. Transmitter power is only 50 watts or less. What's the signal?
GPS satellites transmit two low power radio signals, designated L1 and L2. Civilian GPS uses the L1 frequency of 1575.42 MHz in the UHF band. The signals travel by line of sight, meaning they will pass through clouds, glass and plastic but will not go through most solid objects such as buildings and mountains.
A GPS signal contains three different bits of information — a pseudorandom code, ephemeris data and almanac data. The pseudorandom code is simply an I.D. code that identifies which satellite is transmitting information. You can view this number on your Garmin GPS unit's satellite page, as it identifies which satellites it's receiving.
Ephemeris data, which is constantly transmitted by each satellite, contains important information about the status of the satellite (healthy or unhealthy), current date and time. This part of the signal is essential for determining a
The almanac data tells the GPS receiver where each GPS satellite should be at any time throughout the day. Each satellite transmits almanac data showing the orbital information for that satellite and for every other satellite in the system.
Sources of GPS signal errors
Factors that can degrade the GPS signal and thus affect accuracy include the following:
Ionosphere and troposphere delays — The satellite signal slows as it passes through the atmosphere. The GPS system uses a built-in model that calculates an average amount of delay to partially correct for this type of error. Signal multipath — This occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing errors. Receiver clock errors — A receiver's built-in clock is not as accurate as the atomic clocks onboard the GPS satellites. Therefore, it may have very slight timing errors. Orbital errors — Also known as ephemeris errors, these are inaccuracies of the satellite's reported location. Number of satellites visible — The more satellites a GPS receiver can "see," the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. GPS units typically will not work indoors, underwater or underground. Satellite geometry/shading — This refers to the relative position of the satellites at any given time. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Poor geometry results when the satellites are located in a line or in a tight grouping. Intentional degradation of the satellite signal — Selective Availability (SA) is an intentional degradation of the signal once imposed by the U.S. Department of Defense. SA was intended to prevent military adversaries from using the highly accurate GPS signals. The government turned off SA in May 2000, which significantly improved the accuracy of civilian GPS receivers.
What is WAAS?
You've heard the term WAAS, seen it on packaging and ads for Garmin® products, and maybe even know it stands for Wide Area Augmentation System. Okay, so what the heck is it? Basically, it's a system of satellites and ground stations that provide GPS signal corrections, giving you even better position accuracy. How much better? Try an average of up to five times better. A WAAS-capable receiver can give you a position accuracy of better than three meters 95 percent of the time. And you don't have to purchase additional receiving equipment or pay service fees to utilize WAAS.
The origins of WAAS
The Federal Aviation Administration (FAA) and the Department of Transportation (DOT) are developing the WAAS program for use in precision flight approaches. Currently, GPS alone does not meet the FAA's navigation requirements for accuracy, integrity, and availability. WAAS corrects for GPS signal errors caused by ionospheric disturbances, timing, and satellite orbit errors, and it provides vital integrity information regarding the health of each GPS satellite.
How it Works
WAAS consists of approximately 25 ground reference stations positioned across the United States that monitor GPS satellite data. Two master stations, located on either coast, collect data from the reference stations and create a GPS correction message. This correction accounts for GPS satellite orbit and clock drift plus signal delays caused by the atmosphere and ionosphere. The corrected differential message is then broadcast through one of two geostationary satellites, or satellites with a fixed position over the equator. The information is compatible with the basic GPS signal structure, which means any WAAS-enabled GPS receiver can read the signal.
Who benefits from WAAS?
Currently, WAAS satellite coverage is only available in North America. There are no ground reference stations in South America, so even though GPS users there can receive WAAS, the signal has not been corrected and thus would not improve the accuracy of their unit. For some users in the U.S., the position of the satellites over the equator makes it difficult to receive the signals when trees or mountains obstruct the view of the horizon. WAAS signal reception is ideal for open land and marine applications. WAAS provides extended coverage both inland and offshore compared to the land-based DGPS (differential GPS) system. Another benefit of WAAS is that it does not require additional receiving equipment, while DGPS does.
Other governments are developing similar satellite-based differential systems. In Asia, it's the Japanese Multi-Functional Satellite Augmentation System (MSAS), while Europe has the Euro Geostationary Navigation Overlay Service (EGNOS). Eventually, GPS users around the world will have access to precise position data using these and other compatible systems.
© 2005 http://www.crappie.com/wwwfish/crappie/messages/3984.html
There is a cone of sound waves (think of a sugar ice cream cone or a dunce hat or one of those highway construction cones) that goes out from the transducer to the bottom of the lake then the sound wave bounces off the bottom and back up to the transducer in a straight line ( the sound waves that are detected have to come back in a straight line to the transducer or they won't be detected.
Now anything that is on the bottom that is hit by the sound waves will reflect those sound waves back in all directions. Those sound waves from that object that go to the transducer will be the ones that are received by the transducer. Now a flasher will show each sound wave that is reflected back according to the total travel time (distance) from the transducer down to the object and back to the transducer divided by two) Since we know the speed of sound in water we can calculate the depth by measuring the time traveled to the bottom and back up again to the transducer. Easy right? Now a graph can't show the entire cone of influence. It has to show the shortest distance to the bottom and cut off the other areas. But on a flat that won't make much difference. Anything in the cone of influence will show up according to how far away it is from the transducer.
In shallow water you may only see a 2ft section of the lake bottom. In 100ft water you may see 33ft section (circle) of the lake bottom. Anything (fish) that is in between the bottom of the lake and the transducer and can reflect sound waves off it and back up to the transducer will show up as an echo according to how far away it is from the transducer.
Now when you are moving the object will be shown on the graph as soon as the sound hit's it and travels back up to the transducer and it sent to the depth finder unit's computer and is displayed on the graph or the flasher unit. That could take just a few milliseconds.
So depending on if your moving our standing still and how fast you are moving the fish that you detect may still be 10ft under your boat or 10 ft out in front of your boat but still in the cone of influence. Objects that are in deeper water can be further away from the boat in any direction. In shallow water with a small cone angle (small cone of influence) the object will almost have to be right under the transducer to be hit by the sound waves and show up on the graph. So those objects will be right under the transducer. If you are going 60 mph over the lake then you are traveling 88.1 ft/sec and the object will be way behind your boat in one second. Remember it takes longer for the sound waves to travel to the bottom and back up to the transducer in deep water than it will in shallow water and the time to process the signal and display it on the graph is probably constant or so small to be discounted. In one second I would think that the signal could easily be bounced off the bottom and received and process and displayed on the screen. Also remember that the way you mount your transducer will influence what part of the bottom you will see. Imagine a powerful flashlight beam of light mounted to your transom of your boat. That beam of light can be pointed anyway left right up or down. You want the beam to point straight down or slightly forward (maybe 2 deg or less) towards the front of your boat so that you can catch the reflected beam in the transducer as you are moving forward at high speed.
The transducer must be in contact with the water at all times and there must Not be any air bubbles between the transducer face and the water. Air bubbles will disrupt the sound waves. Sound travels much better in water than it does in air. Air bubbles will slow or even stop the sound waves from going out into the water and then there is no way you can receive an echo if the sound is not going out of the transducer.
I would go to the www.garmin.com web site or the Humminbird.com web site and see if you can find the depth finder tutorials there and read up on this so that you really understand the scientific principles of sonar.
The fish could be anywhere in a circle of 33ft around your boat when you are sitting still in 100ft of water.
Fishfinder Buying Guide
Roaming a lake in your boat fishing at random locations often results in disappointment. Adding a fishfinder to your fishing arsenal greatly increases your chances of having an enjoyable time on the water. From basic fishfinder models under $100 to elaborate color display, GPS enhanced, and 3D readout versions.
Fishfinders, also called depth finders, are an important tool for the fisherman. This device sends a sound wave into the water by way of the transducer. The sound wave reflects off an object such as a fish, or the bottom, and is detected by the transducer also. These echoes are interpreted by the fishfinder and sent to the display. This simple process can provide you with a wealth of information about the unseen region below the water's surface.
The typical fishfinder can reveal a wide range of underwater items. Single fish, schools of fish, bottom composition (soft, rocky), thermoclines (a large change in water temperature), weeds, many types of structure (stumps, wrecks, drop offs, mounds), and much more. Fishfinders with added features can also provide surface water temperature, speed, barometric pressure, and location
Choose Your Fishfinder Equipment
Fishfinder manufacturers make a range of models to suit the far ranging needs of fisherman. You can spend less than $100 or more than $2000 depending on the degree of features you require.
Your individual fishing style will dictate what fishfinder features you should select.
The two major decisions you'll have to make are regarding the transducer and display.
• Do you need wide beam, narrow beam, both, or specialized beam?
The transducer sends down a sound wave usually in the shape of a cone. Think of an ice cream cone with the pointed end attached to your transducer and the open, round end, extending down into the water all the way to the bottom. A narrow beam usually has an angle of about 20 degrees. If you are in 20 feet of water, that would translate into a circle on the bottom about 7 feet across. If you had a wide beam transducer (usually about 60 degree angle), it would form a circle on the bottom 22 feet across. Your fishfinder can only give you information on objects that are within the cone. The wider beam covers more area under water and can locate more fish within its larger cone. The drawback of the wider beam is that it looses strength much quicker. Because of this, it cannot go as deep as the narrow cone. The narrow cone can penetrate water much deeper and even in shallower water; can give more information on the composition of the bottom (mud, weed, rock, etc.)
The best of both worlds is the dual beam (also called dual frequency), that combines both features into one transducer.
There are also specialized transducers. Some have multiple beams (4 or more) that cover a very large area underwater and can create a 3D image on the display. There are also side beam transducers that actually shoot their beam to the sides to increase the search area for fish.
• How will you mount your transducer?
The transducer that is included with the fishfinder you purchase will probably be one that attaches to the transom of your boat. If you have a single hulled fiberglass boat, you can usually mount the transducer to the inside bottom of your boat with epoxy. This is referred to as,"shooting through the hull" mounting.
• It's all about pixels!
The more pixels you get, the more detail you'll see, and the more money you'll spend. A pixel is the smallest dot (or square) on the display screen. A low priced model may list their display as 160V x 132H. That would be a display that is 160 pixels vertically and 132 pixels horizontally. But even with this low priced model, that amounts to a screen with 21,120 dots on it. A higher priced fishfinder may have 640V x 320H which would squeeze about 10 times more dots on the screen giving you better resolution.
Each pixel can have varying degrees of black. Low priced fishfinders may have no greyscale at all or a 4 level grey scale. Higher priced models may have 12 levels of grey for each pixel.
Color has its price. You will pay more for a color display. You will also pay in the amount of resolution you get. The typical color display will cost more and have fewer pixels than a similar black and white model. But instead of 12 levels of grey, each pixel may have up to 256 color choices.
Every website or auction or store should have a good screenshot of the fishfinder's display. You'll have to judge for yourself whether you want color or black and white, and what degree of resolution you require.
• Other display features: There is usually a lengthy list of display features for a fishfinder. You'll have to decide if any of them are important to you.
The power of the fishfinder determines its maximum usable depth. A 100 watts of power can reach up to 600 feet. While a 500 watt model that can go to 1500 feet. Salt water absorbs more energy so higher power models are preferred.
Portable fishfinders are entirely self-contained. The fishfinder comes in its own carrying case with battery power supply. The transducer is attached to the transom by way of a suction cup.
GPS will be discussed separately below, but is a major decision in the buying process.
Fishfinder manufacturers that you see most often are Eagle, Garmin, Humminbird, and Lowrance. Other manufacturers include Bottomline, Furuno, Interphase, Navman, PinPoint, Raymarine, Simrad, and Sitex.
These are all the extra features manufacturers attach to their fishfinders to make them better or different than their competition. They include things like: backlit screen, adjustable display speed, freeze frame, and many more.
Add GPS for the Ultimate Fishing Tool
The Global Positioning System (GPS) uses information it receives from satellites to calculate your exact position. Unlike satellite TV which charges a subscription fee, the GPS radio signal is free for everyone to use.
Affordable GPS is now one of those "must have" fishing items. Having one unit on your console that is both a fishfinder and a GPS is economical and a real space saver. Just like fishfinder features, the GPS component can range from basic features to elaborate detail with color background maps.
The three main reasons you should have GPS
• Saving hot spot locations: This is the biggest feature for the fisherman. The ability to find a hot fishing spot, mark it on your GPS and be able to return to the same spot in the future is a powerful feature. Most GPS capable fishfinders give you the ability to mark hundreds or thousands of spots (called waypoints) for future use.
Example: In the middle of Lake Erie are some sunken train cars. They were pushed off of a barge to dispose of them decades ago. Walleye stick to this structure like a magnet. Finding this spot out in open water without a fishfinder and GPS is impossible. If you have just a fishfinder, you may be able to find it, but it takes a lot of time zigzagging around until to happen to go over it. This wastes a lot of valuable fishing time. With a GPS, your fishfinder GPS combo gives you a heading and a distance that will put you right on top of it with no wasted time.
How Close Will a GPS Get You? Your basic GPS will get you within about 50 feet of your waypoint. Most GPS units now come with WAAS. This enhancement adds additional accuracy to your location and can get you within 10 feet of your waypoint every time.
• Navigation: If you need to refer to charts to navigate your way, you should select a fishfinder GPS combo unit with background maps and charts included.
• Safety: When you start your day of fishing, you mark your starting point with a waypoint on your GPS. You are now free to fish wherever you choose with the confidence that your GPS can point you home with ease. You may have followed a random path of fishing locations throughout the day, lost sight of land, or severe weather has rolled in limiting your visibility and your GPS can tell you exactly what heading to go and how far away "home" is.
New marine radios have a feature that allows you to connect your GPS fishfinder combo unit to your marine radio. Should you have to activate your radio's DSC distress feature, it can transmit your exact location to get help to you the quickest.
GPS Functional or GPS Ready? Some fishfinders are GPS functional right out of the box. Some fishfinders are GPS "ready". They have the GPS software and functions built into the unit already, but require you to purchase something extra (usually the antenna/receiver) to activate the GPS features.
Every fishfinder is ready to use right out of the box. The transducer, cables, and mounting hardware are included. But you may desire some added features to improve its usefulness.
Some of the most common accessories are:
• Transducer replacement: The transducer that comes with your fishfinder is usually the only one you will ever need. All manufacturers offer alternate transducers.
• Speed sensor: If you don't have GPS, adding a speed sensor can be quite helpful if your fishing method includes trolling.
• Search for fishfinder, fish finder, & depth finder to find the most listing.
• Humminbird has no "G"
Large area generalizations...I have found that the 3D finders work the best for me for giving me a "generalization" of an area. The biggest things to remember are....
1. How the display relates to the position of your boat.
2. How accurate the display is due to the combination of transducer and the settings you make on the finder.
Mind you...that is my personal experiences...and in no way may it end up being what any of you experience
Life Member David BB Linkmeister US Army '78-'85 West Central Wisconsin