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Appendix A
Selecting a Transducer
Transducers
The transducer acts as the eyes and ears of your new sonar. Proper transducer selection and
installation are critical to the operation of your unit. The transducer transmits sound waves toward the
bottom in a cone shape. The larger the cone angle, the larger the coverage area at a given depth.
A wide cone angle transducer works best in shallow water. The wide cone angle provides a large
coverage area, but at a decreased bottom resolution. In deeper water this can result in a large dead zone
where fi sh cannot be seen. A narrow cone angle transducer is better suited to deep-water installations.
The narrow cone angle provides a smaller viewing area (compared to a wide cone angle transducer at
the same depth) with improved bottom resolution and a smaller dead zone. Dual frequency transduc-
ers give you the best of both wide and narrow cone angles.
Included in the GPSMAP 188/188C/238 Sounder (with transducer) package is a 200/50 kHz
dual frequency 10/40° cone angle, temperature sensing, transom mount transducer. This transducer
provides good all-around performance. Since many mounting locations vary, listed below are a variety
of optional transducers and accessories which are available from your local dealer or Garmin:
• 200/50 kHz, 15/45°, bronze, thru-hull, depth, temp, speed
• 200/50 kHz, 15/45°, bronze, thru-hull/long stem, depth, temp, speed
• 200/50 kHz, 15/45°, bronze, thru-hull mount, depth only
• 200/50 kHz, 15/45°, plastic, transom mount, depth, temp, speed
• 200/50 kHz, 15/45°, bronze, thru-hull mount, depth only
• 200/50 kHz, 15/45°, plastic, transom mount, depth, temp
• 200/50 kHz, 15/45°, plastic, in-hull adjustable mount, depth, only
• Speed Sensor
• Temperature Probe
• Thru-hull fairing block
• 10 ft. Extension cable for transducers
• 20 ft. Extension cable for transducers
X
X
dead zone
fish notseen
Wide coneangle
Narrow coneangle
188188C238 Manual Part 2.indd 96 6/30/2003, 3:32:41 PM