waecE-LEARNING
Electronics Paper 2, Nov/Dec. 2011  
Questions: 1 2 3 4 5 6 7 8 9 10 Main
General Comments
Weakness/Remedies
Strength















Question 4

(a)      Explain the following processes in a radio receiver:
          (i)      demodulation;
          (ii)      automatic frequency control;
          (iii)     automatic gain control.
(b)     State two advantages of F.M. over A.M.

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OBSERVATION

The expected answers were:

(i)      Demodulation: It is a means by which the audio information

          is extracted or removed from the carrier signal.
(ii)      Automatic frequency control: It is a means by which a portion
        of the output frequency of the IF stage of an FM receiver is detected and used to control the receivers         oscillator frequency to ensure a constant IF frequency.
(iii)     Automatic Gain Control: It is a means by which the amplitude
          of the IF signal is deflected into a d.c. voltage to maintain a
          constant output(volume).

 Advantages of Frequency Modulation over Amplitude Modulation

  1. All types of noise and interferences are eliminated.
  2. The modulated signal contains all fundamental and harmonic frequency of the signal.
  3. Less power is needed in the modulation process.

The question was on Communication System. It was popular with the candidates. The performance of the candidates was not encouraging.

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