MCQOPTIONS
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MCQOPTIONS
This section includes 551 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. |
If the instantaneous RF potentials on the two sides of a magnetron cavity are of opposite polarity, the operation is in the |
| A. | π mode |
| B. | π/2 mode |
| C. | 2π mode |
| D. | π/4 mode |
| Answer» B. π/2 mode | |
| 152. |
If k-factor is greater than 1, the array beam is bent |
| A. | Away from the earth |
| B. | Towards the ionosphere, |
| C. | Towards the earth |
| D. | Towards the outer space |
| Answer» D. Towards the outer space | |
| 153. |
Which causes multipath or frequency selective fading? |
| A. | Small reflector |
| B. | Nearer reflector |
| C. | Further reflector |
| D. | Large reflector |
| Answer» E. | |
| 154. |
In a pulsed radar set, the STC circuit is used to |
| A. | Improve the target bearing resolution |
| B. | Increases receiver sensitivity for echoes from targets |
| C. | Vary the pulse frequency in order to control the maximum target |
| D. | Reduce interference from the effects of sea return |
| Answer» E. | |
| 155. |
Rainfall is an important factor for fading of radio waves at frequencies above |
| A. | 10 GHz |
| B. | 100 GHz |
| C. | 1 GHz |
| D. | 100 MHz |
| Answer» B. 100 GHz | |
| 156. |
A shipboard equipment which measures the distance between the ship’s bottom and the ocean floor. |
| A. | Fathometer |
| B. | Echosounder |
| C. | LORAN |
| D. | SONAR |
| Answer» E. | |
| 157. |
A reflex klystron is oscillating at the frequency of its resonant cavity. If the reflector voltage is made slightly less negative, the |
| A. | Oscillation will cease |
| B. | Output power would increase |
| C. | The frequency will decrease |
| D. | Bunching would occur earlier in time |
| Answer» D. Bunching would occur earlier in time | |
| 158. |
Theoretically electromagnetic radiation field strength varies in inverse proportion to the square of the distance, but when atmospheric attenuation effects and the absorption of the terrain are taken into account the attenuation can be as high as the inverse ___________ power of the distance. |
| A. | Third |
| B. | Fourth |
| C. | Fifth |
| D. | Sixth |
| Answer» E. | |
| 159. |
In a radar-set receiver, the usual mixer stage is |
| A. | And FET |
| B. | A tunnel diode |
| C. | A silicon crystal |
| D. | A Rochelle salts crystal |
| Answer» D. A Rochelle salts crystal | |
| 160. |
The Gunn diode oscillator |
| A. | Is capable of generating continuous microwave power of the order of kilowatt |
| B. | Generates frequencies which are below 100 MHz |
| C. | Operates over a positive resistance characteristic |
| D. | Depends on the formation of charge domain |
| Answer» E. | |
| 161. |
What is the purpose of the electromagnetic field which surrounds a traveling-wave tube? |
| A. | To accelerate the electron |
| B. | To velocity modulate the electron beam |
| C. | To keep the electrons from spreading out |
| D. | To slow down the signal on the helix |
| Answer» D. To slow down the signal on the helix | |
| 162. |
What allow microwave to pass in only one direction? |
| A. | RF emitter |
| B. | Capacitor |
| C. | Varactor-triac |
| D. | Ferrite emitter |
| Answer» E. | |
| 163. |
The aquadag coating on the inside of PPI tube is used |
| A. | To focus the beam of primary electrons |
| B. | To shield the electron beam from unidirectional magnetic |
| C. | As a second anode and to prevent the build-up of secondary field |
| D. | All of these |
| Answer» D. All of these | |
| 164. |
The antenna separations (in meters) required for optimum operation of a space diversity system can be calculated from:where R = effective earth radius (m) and L = path length (m) |
| A. | S = 2λR/L |
| B. | S = 3λR/L |
| C. | S = λR/RL |
| D. | S = λR/L |
| Answer» C. S = λR/RL | |
| 165. |
When it is desired that short-range targets be clearly seen on a pulsed-radar set, it is important that the receiver and display system have |
| A. | A long time constant |
| B. | Low-pass filters |
| C. | The shortest possible time |
| D. | The restricted high-frequency response |
| Answer» D. The restricted high-frequency response | |
| 166. |
Coupling into and out of a traveling-wave tube can be accompanied by a |
| A. | Waveguide match |
| B. | Cavity match |
| C. | Direct coax-helix match |
| D. | All of the above |
| Answer» E. | |
| 167. |
Which device has internal positive feedback? |
| A. | Two cavity klystron amplifier |
| B. | Multi-cavity klystron amplifier |
| C. | Reflex klystron amplifier |
| D. | All of the above |
| Answer» D. All of the above | |
| 168. |
If other parameter are constant, transmission loss at 5 GHz as compared to that at 0.5 GHz is |
| A. | 700 dB more |
| B. | 100 dB less |
| Answer» B. 100 dB less | |
| 169. |
A PIN diode can be used |
| A. | as a shunt mounted switch |
| B. | as a series mounted switch |
| C. | both as series or shunt mounted switch |
| D. | non of the above |
| Answer» D. non of the above | |
| 170. |
The electric field in a TWT due to applied signal |
| A. | is directed along the helix axis |
| B. | is directed radially from helix axis |
| C. | is inclined to the helix axis by about 60° |
| D. | is inclined to the helix axis by about 45° |
| Answer» B. is directed radially from helix axis | |
| 171. |
Which of the following is used in integrated circuits? |
| A. | Twin wire line |
| B. | Shield cable |
| Answer» B. Shield cable | |
| 172. |
Consider the following statements Fading of signals is generally greatest near radio horizon.Fading of signals is generally greatest in shadow zone.Fading is small when a good optical path is present. Which of the above statements are correct? |
| A. | 1, 2 and 3 |
| B. | 1 and 2 only |
| C. | 1 and 3 only |
| D. | 2 and 3 only |
| Answer» B. 1 and 2 only | |
| 173. |
In laboratory experiment the output from reflex klystron is moderated by square wave because |
| A. | it prevents frequency modulation |
| B. | detector circuit is less complicated |
| Answer» C. | |
| 174. |
Assertion (A): Impatt diode can be used in both amplifiers and oscillators.Reason (R): Impatt diode has a low resistance. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 175. |
A microstrip line has dielectric having relative permittivity ‚ààr. The effective dielectric constant is |
| A. | more than ‚ààr |
| B. | equal to 1 |
| C. | less than ‚ààr |
| D. | either a or b |
| Answer» D. either a or b | |
| 176. |
TE10 mode of propagation of electromagnetic energy in waveguides can be thought of as |
| A. | three TEM waves travelling along length of wave-guide |
| B. | One TEM wave travelling along length of wave guide and one TEM wave propagation in the transverse plane |
| C. | One TEM wave travelling along the length of wave guide and two TEM waves |
| D. | none of the above |
| Answer» D. none of the above | |
| 177. |
A line of length slightly longer than and open circuited at far end behaves as |
| A. | L and C in series |
| B. | L and C in parallel |
| Answer» B. L and C in parallel | |
| 178. |
Which part of radio spectrum is more crowded? |
| A. | Lower frequency part |
| B. | Higher frequency part |
| C. | Both (a) and (b) |
| D. | None of these |
| Answer» E. | |
| 179. |
Power gain of a multicavity klystron amplifier is |
| A. | more than 30 dB |
| B. | causes retardation of all electrons |
| C. | causes acceleration of some electrons and retardation of others |
| D. | none of the above |
| Answer» B. causes retardation of all electrons | |
| 180. |
Two identical hybrid tees are joined as shown in the given figure. If 16 mW power is fed into port 1, the power output at ports 2 , 3, 1', 2', 3' respectively is |
| A. | 0, 8, 2, 2, mW |
| B. | 8, 2, 4, 2, 0 mW |
| Answer» C. | |
| 181. |
Assertion (A): A line of length and short circuited at far end has an input impedance of infinity.Reason (R): A line of length and short circuited at far end behaves as a parallel resonant circuit. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» B. Both A and R are correct but R is not correct explanation of A | |
| 182. |
If the repeller voltage in a klystron oscillator is increased the transit time of electron |
| A. | will be increased |
| B. | will be decreased |
| C. | will remain the same |
| D. | either (a) or (b) |
| Answer» D. either (a) or (b) | |
| 183. |
In microwave communication links the fading due to rain occurs. The methods to solve this problem include |
| A. | antenna replacement and feed correction |
| B. | amplitude trimming and phase correction |
| C. | polarization shifting and code diversity |
| D. | path diversity and frequency diversity |
| Answer» E. | |
| 184. |
A rectangular waveguide has width a. Then at the cutoff frequency (with corresponding wave length λc) |
| A. | |
| B. | a = λc |
| Answer» B. a = Œªc | |
| 185. |
Assertion (A): In TE10 mode the cutoff frequency of rectangular waveguide is where a is the broad dimension and c is velocity of light.Reason (R): TE10 mode is the dominant mode in rectangular waveguide. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 186. |
A circular waveguide carries TE11 mode whole radial electric field is given byEr = E0j1(r) sin Φ V/mwhere r is radial distance in cm from the axisThe cut off wavelength is |
| A. | 2 p cm |
| B. | 8 cm |
| Answer» B. 8 cm | |
| 187. |
Assertion (A): A backward wave oscillator can be used as a sweep generator.Reason (R): The frequency of oscillation of a backward wave oscillator can be changed by varying the voltage which controls the beam velocity. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R are correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» B. Both A and R are correct but R is not correct explanation of A | |
| 188. |
Directive gain of elementary doublet is |
| A. | 100 |
| B. | 10 |
| C. | 1.5 |
| D. | 0.5 |
| Answer» D. 0.5 | |
| 189. |
If in line the characteristic impedance becomes real. |
| A. | 1 |
| B. | |
| C. | a + b |
| D. | p(a + b) |
| Answer» B. | |
| 190. |
A disadvantage of microstrip line as the connections of compared to strip line is that former |
| A. | do not lend themselves to printed circuit |
| B. | are more likely to radiate |
| C. | are bulky |
| D. | are more expensive and complex |
| Answer» C. are bulky | |
| 191. |
Microwaves are used for |
| A. | TV systems |
| B. | all of the above |
| C. | the spacing between adjacent turns is very large |
| D. | the spacing between adjacent turns approaches zero |
| Answer» E. | |
| 192. |
A square waveguide carries TE11 mode whose axial magnetic field is given by Hz = H0 , where the guide dimensions are in cms. The cut off frequency of the mode is |
| A. | 5 GHz |
| B. | 7.5 GHz |
| C. | 6.5 GHz |
| D. | 8 GHz |
| Answer» C. 6.5 GHz | |
| 193. |
When a line is loaded the characteristic impedance is equal to |
| A. | (R + jωL)(G + jωC) |
| B. | |
| Answer» C. | |
| 194. |
In a TWT the axial component of electric field advances along the tube |
| A. | at a velocity that is about 50% of speed of light |
| B. | at a velocity that may be even more than speed of light |
| C. | 20 dB more |
| D. | 20 dB less |
| Answer» C. 20 dB more | |
| 195. |
In a Gunn diode oscillator drift velocity of electron is 107 cm/s and active region length is 10 x 10-4 cm. The natural frequency of oscillation is |
| A. | 1 GHz |
| B. | 10 GHz |
| C. | Both A and R are correct and R is correct explanation of A |
| D. | Both A and R are correct but R is not correct explanation of A |
| Answer» E. | |
| 196. |
In a multicavity klystron amplifier the signal to be amplified develops an ac voltage of signal frequency across the gap in buncher cavity |
| A. | 1 |
| B. | |
| C. | short circuit |
| D. | complex impedance |
| Answer» B. | |
| 197. |
A branched duplexer requires |
| A. | TR tubes |
| B. | ATR tube |
| C. | both TR and ATR tube |
| D. | none of the above |
| Answer» D. none of the above | |
| 198. |
VTM stands for voltage tunable magnetron. |
| A. | 1 |
| B. | |
| C. | Microstrip line |
| D. | Coaxial line |
| Answer» B. | |
| 199. |
A rectangular waveguide has a discontinuity in the form of reduced narrow dimension. In the equivalent circuit this discontinuity can be represented by |
| A. | a shunt resistance at the discontinuity |
| B. | none of the above |
| C. | 1 |
| D. | |
| Answer» B. none of the above | |
| 200. |
At millimeter wavelength the favoured mode in circular wave guide is |
| A. | TE20 |
| B. | TE21 |
| C. | it is easy to generate a square wave |
| D. | crystal diode operates in square law region of i-v characteristics |
| Answer» B. TE21 | |