55.A phase-locked loop (PLL) is a feedback circuit consisting of a A. phase detector. B. low-pass filter. C. VCO. D. all of the above Hint: A phase-locked loop is a feedback system combining a voltage controlled oscillator (VCO) and a phase comparator so connected that the oscillator maintains a constant phase angle relative to a reference signal. As the name suggests PLL, if the detected phase is having any error/distortion means the LPF filters it. Then the oscillator maintains the constant phase angle. 56.If a 1 MHz carrier is amplitude modulated with a 5 kHz audio signal, the upper-side frequency is ________ kHz. Radio broadcasts are generally Hint: Frequency modulation gives noise free reception and is used for radio broadcasts. 57.Consider the following statements 1.The amplitude of an FM wave is constant 2.FM is more immune to noise than AM 3.FM broadcasts operate in upper VHF and UHF frequency ranges 4.FM transmitting and receiving equipments are simpler as compared to AM transmitting and receiving equipments Which of the above are correct?
Hint: FM equipments are complex as compared to AM equipments. 58.Frequency shift keying is used mostly in A. telegraphy* B. telephony C. satellite communication D. radio transmission Hint:Frequency shift keying (FSK) is a system of frequency modulation used in telegraphy. 59.The rate at which information can be carried through a communication channel depends on Hint: Rate of information depends on bandwidth. 60.A carrier is simultaneously modulated by two sine waves having modulation indices of 0.4 and 0.3. The total modulation index will be 61.A 1000 kHz carrier is simultaneously modulated with 300 Hz, 800 Hz and 2 kHz audio sine waves. Which of the following frequency is least likely to be present in the output? Hint: Frequency present in the sidebands is equal to = fc± fm, f2fm, fc± 3fm62.Which of the following is the indirect way of FM generation?c± .
A. Reactance bipolar transistor modulator B. Armstrong modulator* C. Varactor diode modulator
D. Reactance FM modulator
It generates FM through phase modulation.