Modulation - Analog Communication MCQs

Explanation: For a signal to be transmitted to a distance, without the effect of any external interferences or noise addition and without getting faded away, it has to undergo a process called as Modulation.

Explanation: The signal which contains a message to be transmitted, is called as a message signal. It is a baseband signal, which has to undergo the process of modulation, to get transmitted. Hence, it is also called as the modulating signal.

Explanation: There are two types of modulation : Continous-wave modulation and Pulse modulation.

Explanation: True, In digital modulation, the modulation technique used is Pulse Code Modulation (PCM) where the analog signal is converted into digital form of 1s and 0s.

Explanation: Squelch is a circuit that acts to suppress the audio (or video) output of a receiver in the absence of a sufficiently strong desired input signal. Squelch is added to suppress noise. It is added after detector when there is no carrier.

Explanation: In continuous-wave modulation, a high frequency sine wave is used as a carrier wave.

Explanation: Emitter Modulator operates in class A region. It has very low efficiency. The output power is low so for modulation at high level, it is not suitable.

Explanation: Signal to Noise ratio compares signal power to noise power. It determines how much signal is present in a transmitted wave compared to presence of noise. It is generally expressed in decibels(dB). For a hi-fi system, it should be equal to 50dB.

Explanation: True, The resultant signal after the process of modulation is called as a modulated signal

Explanation: Leak bias is a type of bias in which the input signal draws grid current from a circuit made of resistors and capacitors. Thus, Leak bias is mainly used to prevent excessive grid current in plate modulated amplifiers.