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question_answer1) A sky wave with a frequency 55 MHz is incident on D-region of earth's atmosphere at 45o. The angle of refraction is (electron density for D-region is 400 electron/cm3) [Haryana PMT 2003]
question_answer2) In a diode AM-detector, the output circuit consist of R = 1kW and C = 10 pF. A carrier signal of 100 kHz is to be detected. Is it good
question_answer3) Consider an optical communication system operating at l~800 nm. Suppose, only 1% of the optical source frequency is the available channel bandwidth for optical communication. How many channels can be accommodated for transmitting audio signals requiring a bandwidth of 8 kHz
question_answer4) A photodetector is made from a semiconductor In 0.53Ga 0.47As with Eg = 0.73 eV. What is the maximum wavelength, which it can detect
question_answer5) A transmitter supplies 9 kW to the aerial when unmodulated. The power radiated when modulated to 40% is
question_answer6) The antenna current of an AM transmitter is 8 A when only carrier is sent but increases to 8.96 A when the carrier is sinusoidally modulated. The percentage modulation is
question_answer7) The total power content of an AM wave is 1500 W. For 100% modulation, the power transmitted by the carrier is
question_answer8) The total power content of an AM wave is 900 W. For 100% modulation, the power transmitted by each side band is
question_answer9) The modulation index of an FM carrier having a carrier swing of 200 kHz and a modulating signal 10 kHz is
question_answer10) A 500 Hz modulating voltage fed into an FM generator produces a frequency deviation of 2.25 kHz. If amplitude of the voltage is kept constant but frequency is raised to 6 kHz then the new deviation will be
question_answer11) The audio signal used to modulate 60 sin (2p ´ 106 t) is \[15\sin 300\pi t.\]The depth of modulation is
question_answer12) The bit rate for a signal, which has a sampling rate of 8 kHz and where 16 quantisation levels have been used is
question_answer13) An amplitude modulated wave is modulated to 50%. What is the saving in power if carrier as well as one of the side bands are suppressed
question_answer14) In AM, the centpercent modulation is achieved when
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