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The ILS receiver of an aircraft on approach and flying on the glide path will receive..
  • A
    the same modulation frequency signals from both lobes with the maximum magnitude.
  • B
    the modulation from both lobes at equal depth.
  • C
    the maximum magnitude of the difference between the two amplitudes.
  • D
    no modulated signal because the two lobes cancel each other along the centerline.

Refer to figure.

As seen in the figure, the glide path is indicated by 2 different lobes. A 90 Hz lobe and a 150 Hz lobe.

When both the signals from the 90 Hz lobe and the 150 Hz lobe received at the same strength it means the aircraft will be on the ‘ideal’ glideslope and the glideslope needle will indicate zero.

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