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Figure 4-7.-Transducer installed on a moving ship
MAJOR COMPONENTS - 14030_90

Aviation Electronics Technician 1 (Organizational)
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The submarine reflects an echo of higher pitch than that caused by the particles in the water, which are not moving. When the echo from the oncoming submarine is higher in frequency than the echoes from the reverberations, the Doppler is high. The opposite form of Doppler shift will occur when the submarine is heading away from the transducer. In this case, the pitch of the echo is lower than the pitch of the reverberations. (See figure 4-10.) The degree of Doppler indicates how rapidly the submarine is moving relative to the transducer. For example, a submarine moving directly toward the transducer at 6 knots returns an echo of higher frequency than one moving at only 2 knots. Also, a submarine moving at 6 knots directly at the transducer returns an echo of higher frequency than one moving only slightly at the transducer. Refer to figure 4-11. This figure shows 12 submarines traveling at various speeds and courses with respect to a stationary transducer supported by the helicopter. Notice how the Doppler of each submarine is influenced by its speed and direction. Doppler also makes it possible to distinguish the difference between a wake echo and a submarine echo. Relatively speaking, the submarine’s wake is stationary. Therefore, its wake returns an echo with a frequency different from that of the Doppler shifted submarine echo. AIRBORNE SONAR SYSTEM Learning Objective: Recognize components and operating principles of an airborne sonar system. Figure 4-11-Varying degrees of Doppler effect due to differences in course and speed of submarines. 4-9







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