InterviewSolution
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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
A tweeter should be fed from the input through a |
| Answer» Tweeter is high frequency loudspeaker covering the range above 5000 Hz. | |
| 52. |
The modulation index is, if = 500 Hz, Δ = 2.25 kHz |
| Answer» Δf = 2.25 kHz, fm = 500 Hz . | |
| 53. |
Compact discs use |
| Answer» CD uses optical recording and retrieval. | |
| 54. |
A carrier is phase modulated (PM) with frequency deviation of 10 kHz by a single tone frequency of 1 kHz. If the single tone frequency is increased to 2 kHz, assuming that phase deviation remains unchanged, the bandwidth of the PM signal is |
| Answer» Frequency deviation = 10 kHz, fm = 1 kHz 2(fm + Df) Bandwidth = 22 kHz 2(10 + 1) 22 kHz fm is doubled Hence 22 x 2 44 kHz bandwidth. | |
| 55. |
In a communication receiver, a squelch circuit is normally inserted |
| Answer» Squelch, i.e., muting is added after detector to suppress noise when no carrier is present at input. | |
| 56. |
In PCM, the information lies |
| Answer» Depending on which logic is used. | |
| 57. |
Some advantages of optical fibre cables are Which of the above are correct? |
| Answer» Fibre optic cables have all these advantages. | |
| 58. |
A directional microphone gives an output of 0.5 mV whereas an omnidirectional one gives an output of 0.5 μV in the same position for the same sound pressure. The directivity of the directional microphone is |
| Answer» Directivity = = 60 dB. | |
| 59. |
If E, the energy per bit of a binary digital signal is 10 watt sec. and the one sided power spectral density of the white noise N = 10 W/Hz, then the output SNR of the matched filter is |
| Answer» O/P SNR = 10 log10 [2 x 10-6 x 10-5]. | |
| 60. |
Noise with uniform power spectral density of Nω/H is passed through a filter H(ω) = 2 exp (-J ω ) followed by an ideal low pass filter of bandwidth B Hz. The output noise power in watts is |
| Answer» Output spectral power density = | H(ω) | x I/P spectral power density = 2 x 2N0 4N0 Output power = 4 N0B. | |
| 61. |
In an AM wave the carrier and one of the side bands is suppressed. If = 1, the percentage saving in power is |
| Answer» . | |
| 62. |
A superheterodyne receiver is to operate in the frequency range 550 kHz - 1650 kHz, with the intermediate frequency of 450 kHz. Let denote the required capacitance ratio of the local oscillator and I denote the image frequency (in kHz) of the incoming signal. If the receiver is tuned to 700 kHz, then |
| Answer» Image frequency = 700 + 2 x 450 1600 kHz fmax = 1650 + 450 2100 kHz fmin = 550 kHz + 450 1000 kHz R = 4.41, I = 1600 kHz. | |
| 63. |
The contrast control in colour TV receiver is done by |
| Answer» Luminance amplifier changes the luminance levels and provides contrast control. | |
| 64. |
The requirements of carrier frequency are |
| Answer» Both should have a precise value and low drift. | |
| 65. |
If N bits are lumped together to get an N-bit symbol, the possible number of symbols is |
| Answer» Each bit can have two levels. Hence 2N. | |
| 66. |
The received signal frequency at any time of a super-heterodyne receiver having IF = 456 kHz is 1 MHz. The corresponding image signal is |
| Answer» Image signal frequency = Received signal frequency - 2 x Intermediate frequency. = 1 MHz - 2 x 456kHz 1 MHz - 912 kHz 88 kHz which lies in medium bond. | |
| 67. |
In Vidicon camera tube, the resistance of photoconductive material on the target plate |
| Answer» Light dependent resistor (LDR) has high resistance in darkness and low resistance in brightness. | |
| 68. |
In a satellite transponder the power amplifier feeds power to the transmitting antenna of gain G. If distance of earth is , the power flux density is |
| Answer» Available power is PG and is spread over 4 nd2. | |
| 69. |
The discone antenna is |
| Answer» Discone antenna is a combination of disc and cone. It is omnidirectional and is used in VHF and UHF range especially at airports. | |
| 70. |
The direction of pick up in a CD is |
| Answer» It is linear from centre to edge. | |
| 71. |
A (75 - 50) Ω load is connected to a coaxial line of Z = 75 Ω at 10 GHz. The best method of matching consists of using |
| Answer» A short-circuited stub placed at a suitable distance from load provides best matching. | |
| 72. |
In a colour TV receiver the bandwidth of RF amplifier is |
| Answer» It is kept a little more than channel width so that reception is not restricted. | |
| 73. |
An FM signal with a deviation is passes through the mixer, and has its frequency reduced five fold. The deviation in the output of the mixer is |
| Answer» Δf (frequency deviation) is independent of fm , Δf depends only upon amplitude of message signal. Δf = kf.Am . | |
| 74. |
An analog signal is band limited to B Hz sampled at Nyquist rate and samples are quantized into 4 levels each with probability . The information rate is |
| Answer» . Signal should be sampled at frequency 2B Hz. Hence, information rate = 2 (2B) = 4B bits/s. | |
| 75. |
The HV supply to a TV receiver is 25 kV and the total beam current for the three electron guns is 2000 μA. The power handled by IHVT is |
| Answer» 25 x 103 x 2000 x 10-6 = 50 W. | |
| 76. |
A + 1.9 lens has a focal length of 25 mm. The diameter of lens is about |
| Answer» . | |
| 77. |
If the amplitude of the voltage is kept constant, but its frequency is raised to 6 kHz, the new deviation will be for the modulation index is, if = 500 Hz, Δ = 2.25 |
| Answer» Δf = β x fm 4.5 x 6 kHz 27 kHz. | |
| 78. |
In TV scanning sequence of lines is |
| Answer» Scanning is always from left to right. | |
| 79. |
The frequency response of a microphone means |
| Answer» 100 Hz is taken as standard for specifying the output. | |
| 80. |
Graphic equaliser system in stereophonic systems generally have |
| Answer» Stereo systems have 3 or 4 bands at 300 Hz, 1000 Hz, 10000 Hz etc. in graphic equaliser system. | |
| 81. |
An amplifier operating over a frequency range of 18 to 20 MHz has 10 kΩ input resistance. At a temperature of 27° C, the noise voltage at input of amplifier is (Boltzman constant = 1.38 x 10 J/K) |
| Answer» Using Equation Va = (4 x 1.38 x 10-23 x 300 x 2 x 106 x 104)0.5 = 18.2 x 10-6 V. | |
| 82. |
Some sources of TV programs are Which of the above are actually present in a TV studio? |
| Answer» All these are present. | |
| 83. |
In PCM the amplitude levels are transmitted in a 7 unit code. Sampling frequency is 10 kHz. The bandwidth should be |
| Answer» Bandwidth = (10 x 7) = 35 kHz. | |
| 84. |
In colour television V and U signals are |
| Answer» U = 0.493 (B - Y) and V = 0.877 (R - Y). | |
| 85. |
Two messages , and have a probability of 0.5 each. The entropy is |
| Answer» Entropy = 0.5 log2 2 + 0.5 log2 2 = 1. | |
| 86. |
A TV receiver is 40 cm wide and 30 cm high. The EHT supply required is about |
| Answer» and EHT supply is 1 kV per diagonal inch. | |
| 87. |
In a TV studios, flying spot scanner is a device for |
| Answer» It is used to telecast feature films. Flying spot scanner uses a special low persistence high brightness cathode ray tube. | |
| 88. |
A broadcast radio transmitter radiates 5 kW when the modulation percentage is 60. How much of this is carrier power? |
| Answer» m = 1, | |
| 89. |
A device has two resistances 300 Ω and 200 Ω respectively. The noise voltages due to these two resistance calculated separately are 5.38 μV and 4.38 μV respectively. When both of them are used together, the noise voltage will be |
| Answer» . | |
| 90. |
Directive gain is |
| Answer» Directive gain is the ratio of power density radiated in a particular direction by the antenna to the power density that would be radiated by isotropic antenna. | |
| 91. |
A line has standing waves with a voltage maximum of 35 mV and minimum of 17.5 mV VSWR is |
| Answer» . | |
| 92. |
For a bit rate of 8 kbps, the best possible values of the transmitted frequencies in a coherent binary FSK system are |
| Answer» where i is integer, and nc is fixed integer. fi = Rb(nc + i) (3 + 1) x 8 32 kHz (4 + 1)0.8 40 kHz. | |
| 93. |
If luminance signal Y = 0.3 R + 0.59 G + 0.11 B, the hue of R - Y colour is |
| Answer» R - Y = R - 0.3R - 0.59C - 0.11B = 0.7R - 0.59G - 0.11B. | |
| 94. |
Trap circuits used in video IF amplifier of colour TV are |
| Answer» High Q LC resonant circuit provides high selectivity. | |
| 95. |
In colour TV system the colour sub carrier frequency is 4.43 MHz. |
| Answer» Video monitor does not have RF tuner and IF amplifier stages. | |
| 96. |
A transmitter power of 5 W is increased by 20 dB. The effective radiated power is |
| Answer» or P = 500 W. | |
| 97. |
The percentage saving in power of 100% modulated suppressed carrier AM signal is |
| Answer» m = 1, if carrier is suppressed then . | |
| 98. |
The maximum distance between television transmission and receiving antennas for reasonably good reception should be |
| Answer» Television transmission is governed by line of sight distance which is about 100 km or less. | |
| 99. |
An AM signal is detected using an envelope detector, the carrier frequency and modulating signal frequency are 1 MHz and 2 kHz respectively. An appropriate value for the time constant of the envelope detector is |
| Answer» In envelope detector, for proper detection 10-6 ≤ RC ≤ 250 μ sec. Only 20 m sec satisfies the condition. | |
| 100. |
For signal amplitude modulated to a depth of 100% by a sinusoidal signal, power is |
| Answer» When m = pt = 1.5 Pc | |