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51.

Which among the following is not a reason for the use of antenna coupler?(a) To make the antenna look resistive(b) To provide the output amplifier with correct load impedance(c) To discriminate against harmonics(d) To prevent re-radiation of the local oscillatorI got this question in quiz.I want to ask this question from Practical Aspects of Sampling in chapter Multiplexing & Sampling of Bandpass Signal of Analog Communications

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The correct choice is (d) To PREVENT re-radiation of the local oscillator

Explanation: ANTENNA coupler is a DEVICE connected between a radio transmitter or receiver and its antenna to improve power TRANSFER between them. Antenna coupler is never USED to prevent re-radiation of the local oscillator.
Discussion
52.

Which of the following term is not applied to the Yagi-Uda array?(a) low impedance(b) high gain(c) good bandwidth(d) high reception of signalsI had been asked this question by my college director while I was bunking the class.This question is from Practical Aspects of Sampling in chapter Multiplexing & Sampling of Bandpass Signal of Analog Communications

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Correct answer is (b) high gain

For explanation: A Yagi-Uda antenna is a directional antenna CONSISTING of many parallel elements in a line. It consists of a single DRIVEN element and also contains parasitic elements. It consists of 3 or 4 DIRECTORS and 1 reflector.
Discussion
53.

Why top loading is used with an antenna?(a) to increase its effective height(b) to increase its beamwidth(c) to increase its bandwidth(d) to increase its impedanceThis question was addressed to me in quiz.This intriguing question comes from Practical Aspects of Sampling in division Multiplexing & Sampling of Bandpass Signal of Analog Communications

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The correct choice is (a) to increase its effective HEIGHT

To ELABORATE: Length of an and it’s height are significant parameters for the functioning of the ANTENNA. When length of the antenna is SHORTER than a quarter wavelength (^ʎ⁄4), top loading is used to increase its effective height.
Discussion