Garmin GPSMAP 298C Owner's Manual - Page 87

Using Dual Frequency Dual frequency works best for deep water (or off-shore) applications. The 200 kHz frequency provides great bottom detail. The 50 kHz frequency provides less detailed information, but penetrates to greater depths with the same power. You can choose either or both frequencies to get the information that you want. If you choose dual frequency, the transducer alternates between the 50 kHz and 200 kHz signals. This capability allows you to see the best picture available at any depth. Using Dual Beam Dual beam works best for shallow water (or inland) applications. A dual beam transducer can transmit either a narrow or a wide beam. The water area covered by the transmitted sound waves is determined by the beam width of the transducer and the water depth. The narrow beam provides crisp detail of what is under your boat, and is very helpful if you are fishing in deeper water where the beam covers more area (for example, at a 30-foot depth, the narrow beam covers the area of about a 7-foot circle). USING SONAR > UNDERSTANDING SONAR Narrow Beam Wide Beam The wide beam is more helpful in shallow water, because it gives you a wider view of objects in the water, including areas beyond the sides of your boat. At a 30-foot depth, the wide beam covers the area of approximately a 20-foot circle. GPSMAP 292/298 Owner's Manual 81