Test: Modulation And Detection Of Signals - NEET MCQ

The abbreviation WWW means world wide web in communication.

The process of impressing information by changing the original signal is called ‘modulation’, and it is done in a variety of ways. In all cases the radio waves simply act as a vehicle for the information, so they are commonly called ‘carrier waves’.

Attenuation is a general term that refers to any reduction in the strength of a signal. Attenuation occurs with any type of signal, whether digital or analog. Sometimes called loss, attenuation is a natural consequence of signal transmission over long distances.

A repeater is an automated radio station that extends the range of communications.To use a repeater, a user's radio is configured to receive on the repeater's transmitting frequency, and when the push-to-talk button is pressed, transmit on the repeater's receiving frequency.

Amplitude modulation, Frequency modulation and Phase modulation are used for the carrier wave which is a continuous wave whereas Pulse amplitude modulation, Pulse width modulation and Pulse position modulation is used if the wave is not a continuous one and is in the form of pulses.

For maximum value modulation index can be greater than 1 or it can take any value depending on the amount of carrier present in the overall modulated signal. Maximum value of modulation index in 1. Above 1 over modulation occurs which cause distortion of signal. Minimum value is 0.

In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted.

Given, peak voltage of the carrier signal is V_c​=10V and 
 peak voltage of the modulated signal is V_m​=2×1=2V (as peak voltage =2× amplitude of voltage)
Modulation index is defined as, μ= V_m /V_c​​=2/10=0.0.2

Power remains constant irrespective of the modulation index in case of F.M. signal.

Velocity modulation is then defined as that variation in the velocity of a beam of electrons caused by the alternate speeding up and slowing down of the electrons in the beam. This variation is usually caused by a voltage signal applied between the grids through which the beam must pass.