Where is Modulation done?
A. Radio receiver
B. Transmitter.
C. Between radio receiver and transmitter.
D. None of the above.

Hint: The modulation is done in the transmission of the pictures at4.2GHz of bandwidth.
The modulation is done at the carrier signal while transmitting that signal. Hence the carrier signal properties get modulated.
The receiver section demodulates the modulated signal to extract the original signal.


Complete step-by-step solution:
The modulation is like hiding some signal inside the carrier signal. The modulation changes the shapes of the carrier wave to hide the original message signal.
The process of imposing the input signal into the carrier signal is known as the modulation. There are various kinds of modulation out there. The most common types of modulation techniques are
Amplitude modulation
Frequency modulation
Phase modulation
In amplitude modulation, the height of the signal is modulated hence it is called amplitude modulation.
In frequency modulation, the frequency of the input signal is modulated. In phase modulation, the phase of the signal is modulated. These are the modulation techniques.
Modulation is important for the communication system. There are some needs for modulation signals; it helps to spare the signal from the different transmitter, helps to reduce the antenna height, and helps to transmit the signal over a long distance without any interference.
Hence the Option(B) is the correct answer.

Note:The modulated signal give the noise immunity to the input signals at high frequency
The modulation can be an analog modulation or digital modulation.
The analog modulation has an input sine wave. And digital modulation is a little more complex.