Sonar
In 1957, Carl Lowrance began marketing his original Red Box and Green Box. Using a technology developed for the military, sonar has since taught generations of anglers how to locate fish and how to interpret bottom features represented by various models.

Does sonar technology help anglers locate more fish? That depends on how well it’s understood and used. Without factoring in all the other elements covered in this book, a sonar display won’t get you very far—you’ll be too busy checking out unproductive parts of the lake and then puzzling over display results, to do much productive fishing. But used as an adjunct to what your eyes tell you about lake or river structure, weather, water temperature, and where fish are in relation to the Calendar Period, sonar units can fine-tune the task of locating largemouths.

Original sonars used a lighted wheel, called a flasher. Paper graphs soon followed, drawing intricate pictures of the bottom and fish. Many anglers found them difficult to operate and maintain, however. Yet avid structure fishermen recognized them as far more accurate than other methods.

Today’s sonar units have now come a long way, with greatly improved picture definition, thanks to new screen technologies. New electronic circuitry has improved the speed of readings, approaching “real time.” The latest generation includes new colored displays featuring TFT technologies (thin film transistors) that enhance screen clarity in bright sunlight. This technology is the same as in your flat-screen TV.

Transducers
For most anglers, transducers are those things mounted on the back of boats or placed somewhere in their hulls. They get blamed for poor images, poor high-speed performance, and no picture. But if you know how these small but important objects work and how to make them work better, they will become the objects of interest they deserve to be.

All transducers have one thing in common: They contain a crystal that vibrates in response to electrical current. The crystal converts that current to sound energy, which is emitted at a particular frequency and direction. In the case of fishing sonar, the operating frequency from 50 kHz to 400 kHz is aimed at the lake bottom. When the sound energy bounces back—whether from fish, or from bottom and other structure—it’s reconverted (transduced) to electrical energy. This travels to the locator head, where it’s displayed as an image. Screen images are displayed as cross-sections of depth, and objects that have impeded the sonar unit’s sound waves are displayed at their respective depths.

Discussions of transducers usually center on their frequency and cone angle (beam width). Most freshwater sonar units operate in the 50- to 200-kHz range. Every frequency within this spectrum offers advantages and disadvantages. Manufacturers choose frequencies to optimize particular performances and functions. It’s important to know what these are before choosing a unit.

Cone angle or beam width refers to the diameter of the three-dimensional cone of water covered by the unit’s sonar at a particular depth, which is usually referred to as the “half-power point,” or –3 dB. Think of the cone angle as an inverted sugar cone, with the point as the transducer. A narrow cone angle looks like a narrow ice cream cone, while a wide cone angle looks like a broad one. Depending on frequency, cone angles typically range from about 8 to 50 degrees. Usually the cone angle is narrower at high operating frequency and broader at low frequency. These are physical limits that design can’t overcome.

A Narrow Cone Angle

A cone angle of say, one of fewer than 20 degrees provides more accurate bottom detail with less coverage, while a wide cone angle displays a larger area with perhaps more targets. But those targets are spread out over a larger area, and it’s unclear exactly how close they are to your boat. When you’ve located a fish with a narrow-beam transducer, you know that it’s near or under your boat. Measured at –3 dB, an 8-degree transducer covers an area whose diameter is about 1/6 of water depth (scans a 3-foot circle in 18 feet of water); a 20-degree transducer covers an area whose diameter is about 1/3 of water depth (6-foot circle); a 38-degree transducer, one whose diameter is about 2/3 of water depth (12-foot circle).

The disadvantages of low-frequency systems are that they usually don’t work well in water less than 10 to 15 feet, and that they penetrate deeper water more weakly than high-frequency systems. But a narrow-beam transducer (say, 8 degrees) can concentrate sound energy and reach deep water. In several hundred feet of water, even narrow beams penetrate to significant depths. For example, deep-water anglers on the Great Lakes often prefer low-frequency units. High-frequency systems, however, usually offer better target separation.

Because there are advantages to both designs, a few manufacturers produce sonar units able to operate at dual frequencies. A common dual frequency transducer operates at 50/200 kHz. A second design offers a dual-beam transducer whose frequency stays the same but whose cone width can be set for either 9 or 18 degrees. Yet another design is built around transducers containing multiple crystals of the same frequency; each scans in a different direction—right, left, or center—thus creating a wider beam of coverage.

Transducer Power
Power determines how deeply sonar penetrates; a more powerful unit can send its signal deeper into water. For deep fishing, a 3,000-watt unit performs better than a 200-watt one. The latest units boast up to 8,000 watts peak-to-peak. But how much power do you need? Bottom hardness, fresh or salt water, plankton concentration, interference, and receiver sensitivity are factors affecting the depth to which a unit can penetrate.

Two aspects of sonar power should be factored into your decisions about how much sonar to buy: edge detection and target separation.

Edge detection—The strongest signal is along the axis of the transducer. On the edges of that sound cone, energy decreases. Powerful locators— sonar units— help detect targets at the edges of the cone better than less powerful ones.

Target separation—Another aspect of sonar power is a unit’s ability to detect and display objects like fish, rocks, and weeds. Greater power can drive sound waves to lake bottom in deeper water, making possible the separation of objects that are close together. Most units with midrange frequency can separate targets that are about 3 inches apart in shallow water. That is, if a fish is 4 inches above bottom, a midrange unit can show the fish and bottom as distinct objects. But if a fish lies 2 inches off bottom, fish and bottom are likely to blend into a single image. Similarly, if your boat is floating over three fish all the same distance from the transducer, even though they’re at different depths only one fish will be displayed. Target separation widens in deeper water, so the more powerful a unit is, the greater likelihood that it can bounce off bottom and separate objects in close proximity to each other.

How much edge and target separation to buy depends on where you do most of your fishing. If you rarely fish deeper than 30 feet and bottom there is relatively firm, 300 watts may be adequate for you. If you fish soft-bottomed lakes or deeper water, you’ll get more satisfaction from a 2,000- to 3,000-watt unit.

Interpreting Sonar
The problem with both deep water and soft bottom is the weak signal they return. In deep water, the signal travels a long way on its round-trip from surface to lake bottom and back to the surface again. As it travels, it becomes weaker and therefore harder to detect, translate, and display. On soft bottoms like muck and silt, much of the signal is absorbed by the substrate. To improve readings over such substrates, turn up the unit’s sensitivity in manual mode to a level higher than the default one the unit’s auto mode selected. In water shallower than 5 feet, the return signal can be too strong because of the short distance it travels: In this case, auto mode may not reduce the sensitivity setting enough to produce a clear picture. Instead, the whole screen may “gray out.” To adjust, turn down the sensitivity in shallow water or over a hard bottom, thereby providing a narrower cone angle. In deeper water or over softer bottom, increase sensitivity to provide a broader cone angle.

Weeds provide another set of challenges for controlling sensitivity. Bass fishing along the edges of weedlines or over weedbeds is common. Locators that are set in auto mode have difficulty handling such locations. If you increase the sensitivity to penetrate to the bottom in a weedbed, the screen will be saturated and lacking in detail. Remember that increasing sensitivity raises the unit’s listening ability, not the locator’s power. When you power up in auto mode in dense vegetation, you get a strong return signal because vegetation is a good reflector, sending back a strong signal that lacks detail because of its multiple surfaces. Your unit is on overload. To reduce the unit’s sensitivity around weeds, use the sonar in manual mode, changing its sensitivity settings several times to learn which works best.

The sensitivity control is the locator’s most important function. Learn how it affects what you see on screen, so that the unit is working for and not against you. Head out to your favorite body of water and position your boat in shallow water, deep water, over hard bottom, soft bottom, over rockpiles and in front of weedlines. See how the unit reports back on each of these areas. Adjust its sensitivity settings to see how doing so affects the information displayed. Decide which work best in situations you’re familiar with. Doing so will give you more confidence in your sonar’s capabilities.

Global Positioning Satellite (GPS) Systems
The Global Positioning Satellite system is the most important locating technology to be introduced to fishing since the introduction of the depthfinder. GPS was developed for the U.S. Department of Defense, and its first widespread use was during the Gulf War. Drawing on a network of satellites orbiting some 11,000 miles above the earth, a GPS unit can triangulate locations for latitude and longitude to within 20 to 70 feet.
Not surprisingly, the number of anglers who own GPS units has skyrocketed. Prices have fallen and new technologies have appeared for both boat-mounted and handheld units.

Anglers use GPS for better positioning accuracy, marking spots, mapping, and charting routes within water bodies. GPS mapping systems offer electronic displays of lakes, rivers, and their shorelines. Back in the mid-90s when GPS units first appeared on the sporting goods scene, maps were cartridge-based and quite basic. They displayed freeway systems, state roads, large and midsized lakes, rivers, and medium to large towns. Background maps typically covered the entire U.S. as well as parts of Canada and Mexico. Greater topographic detail became available when manufacturers introduced cartridges that enhanced designated areas on background maps. These provided additional useful navigational information— buoy markers, reefs, channels, and water depths. Extent and detail of coverage varies and certain computer applications are required, so check features before you buy electronic maps.

Cartridge mapping systems are available in chart-by-chart or seamless options. The chart-by-chart method is a digital version of the paper maps you’ve worked with for years, and it carries with it the same problem—differences of scale when you move from one map to another. The seamless method scrolls across a map with a uniform scale. The quality of mapping details is a function of two factors, the electronic file in the map cartridge and the acuity of your display monitor. In the case of a typical LCD screen, the total pixel count and the screen’s ability to react to light are the factors determining detail. Coarse screens may not adequately display all of the information available on a cartridge, particularly small details.

Keep in mind that zooming down to a small scale may not increase detail. It may mean instead that what you saw at 2 miles is only bigger at 0.2 mile, not more detailed. Different levels of detail should appear at different zoom or scale levels. For example, contour lines, small reefs, and islands that may not appear on a 20-mile scale should become visible on a 3-mile scale. Check to make sure that the mapping system you buy offers that capability.

The appearance of CD-ROMs in the GPS lineup means that instead of buying a handful of cartridges to cover all the areas you travel for outdoor activities, you can now cover the entire country in great detail with one or two CDs. When you load a mapping CD—such as Lowrance’s MapCreate or Garmin’s Road and Recreation and MetroGuide U.S.—the program appears on the monitor. Select or outline the area you want transferred to your GPS unit. The transfer is done through a data cable that attaches to the computer’s data port. Mapping programs allow you to create or customize your own maps, so you can choose the details you want displayed—small streams, rural roads, restaurants, street names, navigational aids, state parks, and so on.

Once you’ve selected a map area for downloading, the information is transferred into a “flash memory” (typically, 2 to 8 MB of memory on a blank cartridge or MMC card that fits in your GPS unit). Depending on the level of detail you’ve chosen, a single file can include a state the size of Georgia.

GPS Applications
Marking waypoints is another strength of GPS systems. You can mark important points like home port, boat ramps, rocks, and reefs on your GPS maps so that you can avoid hazards or accurately return to fishing spots again, even in bad weather or at night. Thanks to contour maps offered by such companies as Lakemaster, C-Map, Fishing Hot Spots, Lowrance, and Navionics in cartridge, CD, and website formats, you can add waypoints to existing contour maps. When you’re working on your computer with mapping systems, such as those produced by Fishing Hot Spots and Waypoint Technologies, you can move your mouse to locations and set them as waypoints. The system numbers your waypoints and you can name them for better identification. Marking underwater points, inside turns, and sunken islands is simple. This information can then be downloaded to your GPS unit.

Most GPS units let you place markers or icons on the screen to mark fish or interesting structure for future reference. Most anglers don’t bother to punch in names for locations of caught fish, as they expect them to change. You can enter them on your computer later or log them into a notebook in case of GPS unit failure. GPS also is a safety feature, provided your batteries don’t go dead. Even on familiar waters, anglers can become disoriented in fog, heavy rain, or other severe weather. Waypoints, icons, or saved trails can lead you to your destination. GPS has turned many shoreline casters into open-water anglers, thanks to the technology’s ability to get them back home over featureless, expansive waters.

Underwater Cameras
Today, underwater viewing systems are available with features like lights for night viewing and enhanced camera positioning systems. Many are available for less than the cost of a good sonar or trolling motor, or about the same as a top-of-the line reel.

We’ve found that cameras don’t spook bass as was initially reported. Rather, they often seem curious, swimming up to investigate the apparatus. Closely examining specific cover objects on favorite spots demonstrates that subtle characteristics attract big bass, while other nearly identical areas remain lifeless. We’ve discovered that it isn’t odd to spot bass roaming well above the bottom, sometimes far from cover objects. We also learned that bass do indeed swim down to chase prey.

Beyond mysteries solved, underwater viewing during fishing trips brings an immediate boost of confidence, whether you’re exploring a new lake or preparing for tournament competition. Accurate visualization spawns this confidence, a mindset that inevitably yields more fish.