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MCQOPTIONS
This section includes 1362 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics & Communication Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
c(t) and m(t) are used to generate an AM signal. The modulation index of the generated AM signal is 0.5 then the quantity Total Sideband Power / Carrier Power is |
| A. | 1/2 |
| B. | 1/4 |
| C. | 1/3 |
| D. | 1/8 |
| Answer» E. | |
| 152. |
An FM signal with deviation δ is passed through mixer. Its frequency is reduced five fold. The deviation in output of mixer is |
| A. | 0.28 |
| B. | δ |
| C. | 5 δ |
| D. | very very high |
| Answer» C. 5 δ | |
| 153. |
A signal x(t) = 100 cos (24π x 10³t) is ideally sampled with a sampling period of 50 μ sec and then passed through an ideal low pass filter with cut off frequency of 15 kHz Which of the following frequencies are present at the filter output? |
| A. | 12 kHz only |
| B. | 8 kHz only |
| C. | 12 kHz and 9 kHz |
| D. | 12 kHz and 8 kHz |
| Answer» E. | |
| 154. |
An audio signal (say from 50 Hz to 10000 Hz) is frequency translated by a carrier having a frequency of 10⁶ Hz. The values of initial (without frequency translation) and final (after frequency translation) fractional change in frequency from one band edge to the other are |
| A. | 200 and 1.01 |
| B. | 200 and 10.01 |
| C. | 200 and 100.1 |
| D. | 200 and 200 |
| Answer» B. 200 and 10.01 | |
| 155. |
An amplitude modulated wave is e = 50 (1 + 0.4 cos 1000 t + 0.3 cos 10000 t) cos 10⁷ t |
| A. | 0.5 |
| B. | 0.3 |
| C. | 0.7 |
| D. | 0.4 |
| Answer» B. 0.3 | |
| 156. |
If S represents the carrier synchronization at the receiver and ρ represents the bandwidth efficiency, then the correct statement for the coherent binary PSK is |
| A. | ρ = 0.5, S is required |
| B. | ρ = 1.0, S is required |
| C. | ρ = 0.5, S is not required |
| D. | ρ = 1.0, S is not required |
| Answer» E. | |
| 157. |
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 |
| A. | 120 dB |
| B. | 90 dB |
| C. | 60 dB |
| D. | 30 dB |
| Answer» D. 30 dB | |
| 158. |
A diode detector load consists of 0.01 μF capacitor in parallel with a 5 k ohms resistor. The maximum depth of modulation without diagonal clipping at modulating frequency of 1000 Hz and 10 kHz is |
| A. | 0.76, 0.24 |
| B. | 0.95, 0.3 |
| C. | 0.24, 076 |
| D. | 0.3, 0.95 |
| Answer» C. 0.24, 076 | |
| 159. |
Consider the following applications/ advantages of radar beacons 1. navigation2. target identification3. accurate tracking of enemy targets4. large increase in maximum range Which of the above are correct? |
| A. | 1, 2, 3, 4 |
| B. | 1, 2, 4 |
| C. | 1, 2 |
| D. | 2, 3, 4 |
| Answer» C. 1, 2 | |
| 160. |
Consider the following advantages of phase array radar 1. simple circuitry2. ability to track and scan simultaneously3. ability to track many targets together4. very fast scanningWhich of the above are correct? |
| A. | 1, 2, 3 |
| B. | 1, 3, 4 |
| C. | 2, 3, 4 |
| D. | 1, 4 only |
| Answer» D. 1, 4 only | |
| 161. |
If each frequency component of f(t) is shifted by π/2, the resulting signal is |
| A. | Hilbert transform of f(t) |
| B. | Inverse Hilbert transform of f(t) |
| C. | Laplace transform of f(t) |
| D. | Fourier transform of f(t) |
| Answer» B. Inverse Hilbert transform of f(t) | |
| 162. |
Which statement is incorrect for the signal x(t) = 5 sin (2π x 10³t) sin (2π x 10⁶t)? |
| A. | Upper side band frequency is 1001000 |
| B. | Carrier amplitude is 5 |
| C. | Lower sideband frequency is 990000 |
| D. | x(t) is DSB-SC |
| Answer» D. x(t) is DSB-SC | |
| 163. |
The spectral component of noise associated with kth frequency is given, in the limit as Δf → 0 by nk(t) written as nk(t) = Ck cos (2πk Δft + θk) Consider the following statements as regards Ck and θk 1. Ck and θk are independent of one another2. Ck and θk are independent of the amplitude of a spectral component at a different frequency3. Ct and θk are independent of the phase of a spectral component at a different frequency Which of the above statements are correct? |
| A. | 1, 2 only |
| B. | 1, 3 only |
| C. | 1, 2, 3 |
| D. | 2, 3 only |
| Answer» D. 2, 3 only | |
| 164. |
Some possible functions of AGC in a TV receiver are 1. To increase gain for weak signals2. To decrease gain for strong signals3. To change the contrast when we switch from one channel to other4. To reduce flutter Which of the above are correct? |
| A. | 1, 2, 3, 4 |
| B. | 1, 2, 4 |
| C. | 1, 2, 3 |
| D. | 2, 3, 4 |
| Answer» C. 1, 2, 3 | |
| 165. |
If carrier is modulated by a digital bit stream having one of the possible phases of 0°, 90°, 180°, and 270°, then modulation is called |
| A. | BPSK |
| B. | QPSK |
| C. | QAM |
| D. | MSK |
| Answer» C. QAM | |
| 166. |
If e = 10 sin(10⁸ t + 3 sin 10⁴ t) then modulating frequency is |
| A. | 159 Hz |
| B. | 1590 Hz |
| C. | 1.59 MHz |
| D. | 15.9 MHz |
| Answer» C. 1.59 MHz | |
| 167. |
If there are M messages and each message has probability p = 1/m, the entropy is |
| A. | 0 |
| B. | 1 |
| C. | log₂ M |
| D. | M log₂ M |
| Answer» D. M log₂ M | |
| 168. |
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 k = 1.38 x 10‾²³ J/K) |
| A. | 18.2 μV |
| B. | 182 μV |
| C. | 16.2 μV |
| D. | 162 μV |
| Answer» B. 182 μV | |
| 169. |
SWR for a transmission line is infinity when the load is 1. Short circuit2. Complex impedance3. Open circuit4. Pure reactance Of the above statements: |
| A. | 1, 3, 4 are correct |
| B. | 1 and 3 are correct |
| C. | 2, 3, 4 are correct |
| D. | 1, 2, 4 are correct |
| Answer» C. 2, 3, 4 are correct | |
| 170. |
A narrow band noise n(t) has symmetrical spectrum and has power density spectrum 0.2 x 10‾⁶. The power density of quadrature component is |
| A. | 0.2 x 10‾⁶ |
| B. | 10‾⁷ |
| C. | 4 x 10‾⁷ |
| D. | 5 x 10‾⁸ |
| Answer» C. 4 x 10‾⁷ | |
| 171. |
A three stage telephone switching structure is to have 128 input and 128 output terminals. It has been found that at peak time the utilization probability is 0.1. The number of intermediate links required for non-blocking configuration is 15. If the actual number of intermediate links is 5, the probability of blocking of call is |
| A. | 1% |
| B. | 0.5% |
| C. | 0.2% |
| D. | 0.1% |
| Answer» D. 0.1% | |
| 172. |
A signal m(t) = 5 cos 2π 100 t frequency modulates a carrier. The resulting FM signal is 10 cos {(2π10⁵ t) + 15 sin (2π 100 t)} The approximate bandwidth of the FM would be |
| A. | 0.1 kHz |
| B. | 6 kHz |
| C. | 3.2 kHz |
| D. | 100 kHz |
| Answer» E. | |
| 173. |
Consider the following statements about Yagi Uda antenna 1. It is unidirectional2. Its gain is about 7 dB3. It is used at VLF4. The optimum separation is 0.11 Which of the above are correct? |
| A. | 1 and 2 only |
| B. | 1, 2, 4 only |
| C. | 1, 2, 3, 4 |
| D. | 1 and 4 only |
| Answer» C. 1, 2, 3, 4 | |
| 174. |
If D is diagonal and F is focal length, lens angle θ is |
| A. | θ = tan‾¹ (D/F) |
| B. | θ = 2 tan‾¹ (D/F) |
| C. | θ = tan‾¹ (D/2F) |
| D. | θ = 2 tan‾¹ (D/2F) |
| Answer» E. | |
| 175. |
In VHS format the width of tape is |
| A. | 2" |
| B. | 1" |
| C. | 1/2" |
| D. | 1/4" |
| Answer» D. 1/4" | |
| 176. |
A 100 + j 100 Ω load is to be matched to a line with Z0 = 300 Ω to give SWR = 1. The reactance of stub is |
| A. | j 200 Ω |
| B. | -j 200 Ω |
| C. | j 100 Ω |
| D. | -j 100 Ω |
| Answer» C. j 100 Ω | |
| 177. |
In TV transmitter some possible advantages of IF modulation are 1. The modulator section and visual exciter can be solid state devices2. VSB filter can be introduced at low power level3. The subsequent stages following VSB filter can be tuned permanently for wideband linear operation4. It is economical which of the above are true? |
| A. | 1 and 2 |
| B. | 1, 2 and 3 |
| C. | 2, 3 and 4 |
| D. | 1, 2, 3 and 4 |
| Answer» E. | |
| 178. |
A paraboloid reflector has mouth diameter D meters, wavelength λ meters. Its beam width φ is equal to |
| A. | 70λ/D |
| B. | 70D/λ |
| C. | λ/70D |
| D. | D/70λ |
| Answer» B. 70D/λ | |
| 179. |
A resistor R is in parallel with capacitance C. The rms noise voltage of resistor in the equivalent circuit can be written as |
| A. | kT/C |
| B. | kTC |
| C. | kC/T |
| D. | kT/C² |
| Answer» B. kTC | |
| 180. |
Consider the following test signal patterns 1. Ramp2. Grill3. Grey shades4. Sine pulse5. Picture line up generating equipment Which of the above are used in TV studios? |
| A. | All |
| B. | 1, 2 and 3 only |
| C. | 1, 2 and 5 only |
| D. | 2, 3, 4 and 5 only |
| Answer» B. 1, 2 and 3 only | |
| 181. |
Consider the following functions 1. It detects the AM video carrier IF so as to produce the video signal2. It produces and separates out the inter carrier sound IF of 5.5 MHz3. It amplifies the video signal4. It amplifies the audio signalThe video detector in a colour TV performs which of the above functions |
| A. | 1, 2 and 3 |
| B. | 1, 2, 3 and 4 |
| C. | 1 and 2 |
| D. | 1, 2 and 4 |
| Answer» D. 1, 2 and 4 | |
| 182. |
The PSD and the power of a signal g(t) are respectively Sg(ω) and Pg, the PSD and the power of signal a.g(t) are respectively |
| A. | aS²g (ω) and a²Pg |
| B. | aSg² (ω) and aPg |
| C. | aSg (ω) and a²Pg |
| D. | aSg (ω) and aPg |
| Answer» B. aSg² (ω) and aPg | |
| 183. |
If the ratio of ac to dc load impedance of a diode detector is low, the result will be |
| A. | poor AGC operation |
| B. | poor AF response |
| C. | negative peak clipping |
| D. | diagonal clipping |
| Answer» D. diagonal clipping | |
| 184. |
A sequence x(n) with the z transform X(z) = z⁴ + z² - 2z + 2 - 3z - 4 is applied as an input to a linear, time invariant system with the impulse response h(n) = 2δ(n - 3) where δ(n) is given below. The output at n = 4 is |
| A. | - 6 |
| B. | zero |
| C. | 2 |
| D. | - 4 |
| Answer» C. 2 | |
| 185. |
Fourier series expansion of a real periodic signal with fundamental frequency is given by following equation. It is given that c₃ = 3 + j5. then c-₃ is |
| A. | 5 + j3 |
| B. | -3 - j5 |
| C. | -5 + j3 |
| D. | 3 - j5 |
| Answer» E. | |
| 186. |
A signal m(t) with bandwidth 500 Hz is first multiplied by a signal g(t) where g(t) is given by below equation. The resulting signal is then passes through an ideal low pass filter with bandwidth 1 kHz the output of the low pass filter would be |
| A. | δ(t) |
| B. | m(t) |
| C. | 0 |
| D. | m(t) δ(t) |
| Answer» C. 0 | |
| 187. |
For a three stage cascaded amplifier, having gains of G₁, G₂ and G₃ and noise figures of F₁, F₂, F₃ the overall noise figure |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 188. |
A π matching network for coupling the transmitter output of the antenna is shown in figure.In this C₂ should be tuned for |
| A. | minimum D.C. plate current |
| B. | maximum D.C. plate current |
| C. | maximum RF antenna current |
| D. | specified value of the D.C. plate current |
| Answer» C. maximum RF antenna current | |
| 189. |
Consider the following: 1. A TV receiver antenna should pick up the TV signal and develop maximum voltage from the available strength of signal2. It should reject unwanted signals3. It should not suffer from co-channel interference4. It should have a very narrowband The correct statements are |
| A. | 1 and 2 only |
| B. | 1, 2 and 3 only |
| C. | 1, 2, 3, 4 |
| D. | 2, 3 only |
| Answer» C. 1, 2, 3, 4 | |
| 190. |
Consider the following statements about Rhombic antenna 1. It is non resonant2. It is a broad band antenna3. It is ideally suited for HF transmission Which of the above are correct? |
| A. | 1, 2, 3 |
| B. | 1, 3 only |
| C. | 2, 3 only |
| D. | 1 only |
| Answer» B. 1, 3 only | |
| 191. |
If aspect ratio is 4/3 and number of lines in each frame is 625, the number of picture elements in one frame is |
| A. | 4/3 x 625 |
| B. | 4/3(625)² |
| C. | 625² |
| D. | 3/4(625)² |
| Answer» C. 625² | |
| 192. |
In a two stage cascade amplifier the equivalent noise temperatures are Te1 and Te2. If the gains of the two stages are G1 and G2, the overall noise temperature Te is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 193. |
The carrier frequency will be if L = 50 µH and C = 1 nF. |
| A. | 512 |
| B. | 612 kHz |
| C. | 712 kHz |
| D. | 812 kHz |
| Answer» D. 812 kHz | |
| 194. |
The open loop gain of an amplifier is 50 but is likely to change by 20%. If negative feedback with β = 0.1 is used, the change in gain will be about |
| A. | 20% |
| B. | 10% |
| C. | 4% |
| D. | 0.05% |
| Answer» D. 0.05% | |
| 195. |
If an isotropic source is radiating power P in all directions, the electric field at a distance d from the source is proportional to |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |
| 196. |
A carrier A cos ωct is modulated by a signal mt A cos ω₁t + m₂ A cos ω₂t + m₃ A cos ω₃t. The total modulated power is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 197. |
Which of the following operation are performed on linear queues?1. Testing a linear queue for underflow2. Enqueue operation3. Dequeue operation4. Testing a linear queue for overflow Select the correct answer using the codes given below the lists |
| A. | 1, 2 and 3 |
| B. | 2, 3 and 4 |
| C. | 1, 3 and 4 |
| D. | 1, 2, 3 and 4 |
| Answer» E. | |
| 198. |
Which of the following does not cause losses in optical fibre cables? |
| A. | Stepped index operation |
| B. | Impurities |
| C. | Microbending |
| D. | Attenuation in glass |
| Answer» B. Impurities | |
| 199. |
If B is channel bandwidth, S is signal power and N is the total noise within the channel bandwidth, the channel capacity C of a white band limited gaussian channel is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 200. |
When E1, E2, E3 etc. are the simultaneous modulating voltages, then the total modulating voltage Et will be |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» D. D | |