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antennas produce a space-modulated signal resulting from the vectorial addition of two or more audio signals that vary according to position of the receiving aircraft. The difference between the two modulation depths produce an error current signal in the airborne receiver. When an aircraft follows
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the course line, the difference in the depths of the modulation between the two frequencies is zero. This difference is conventionally displayed by the deflection of a moving coil indicator or needle on an instrument known as a
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In directive systems employing overlapping lobes with modulated signals, a ratio obtained by subtracting from the percentage of modulation of the larger signal the percentage of modulation of the smaller signal and dividing by
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in conjunction with the associated airborne receiving equipment to define a position in airspace. DDM is usually expressed in percentage but may also be expressed in microamperes. The two individual audio
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A modulation depth comparison navigational aid (MDCNA), also known as an
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frequencies and their associated sidebands are 90 and 150
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McGraw-Hill
Dictionary of Scientific and Technical Terms
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to provide guidance to aircraft when on final approach.
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125:"Difference in the depth of modulation".
100:International Civil Aviation Organization
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18:difference in the depth of modulation
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72:(SBO) signal, transmitted from
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83:horizontal situation indicator
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26:instrument landing systems
51:instrument landing system
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39:full scale deflection
95:Amplitude modulation
53:uses the concept of
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157:Radio navigation
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106:Radio navigation
55:space modulation
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68:(CSB), and
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78:glide path
31:modulation
74:localizer
151:Category
89:See also
66:sideband
85:(HSI).
62:carrier
102:(ICAO)
45:Method
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76:and
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22:DDM
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60:A
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35:Hz
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