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.
| 101. |
A square waveguide carries TE₁₁ mode whose axial magnetic field is given by following equation, 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 | |
| 102. |
In terms of R, L, G and C the propagation constant γ of a transmission line is |
| A. | A |
| B. | B |
| C. | c |
| D. | D |
| Answer» C. c | |
| 103. |
In the given figure power meters at A and B indicate 1 mW and 110 μW respectively. VSWR of line is |
| A. | 1.5 |
| B. | 2 |
| C. | 2.5 |
| D. | 3 |
| Answer» C. 2.5 | |
| 104. |
If ρv is reflection coefficient and VSWR is voltage standing wave ratio, then |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» C. C | |
| 105. |
Which of the following are true for magic tee in the given figure select the answer as per given codes1. S13 = S232. S14 = S243. S12 = 04. S34 = 0 |
| A. | 1, 2 and 3 |
| B. | 1, 2 and 4 |
| C. | 2, 3 and 4 |
| D. | 1, 3 and 4 |
| Answer» D. 1, 3 and 4 | |
| 106. |
The magnitudes of OC and SC input impedances of a transmission line an 100 Ω and 25 Ω. The characteristic impedance is |
| A. | 25 Ω |
| B. | 50 Ω |
| C. | 75 Ω |
| D. | 100 Ω |
| Answer» C. 75 Ω | |
| 107. |
Consider the following statements:1. Dissipative attenuator has a fixed value of attenuation.2. Reflective attenuator has a fixed value of attenuation.3. Both dissipative and reflective attenuators are available only with fixed attenuation.4. Both dissipative and reflective attenuators are available with either fixed or variable attenuation. Which of the above are correct? |
| A. | 1 only |
| B. | 1 and 2 |
| C. | 1, 2 and 3 |
| D. | 4 only |
| Answer» E. | |
| 108. |
In directional coupler of the given figure, the terms |S₁₄| and |S₂₃| of scattering matrix are nearly |
| A. | 1 each |
| B. | 0.5 each |
| C. | 0.1 each |
| D. | 1 and 0.5 respectively |
| Answer» B. 0.5 each | |
| 109. |
Consider the following statements 1. Fading of signals is generally greatest near radio horizon.2. Fading of signals is generally greatest in shadow zone.3. 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 | |
| 110. |
A microstrip line has ∈r = 9. The normalised wavelength (λ/λ₀) is about |
| A. | 10 |
| B. | 2 |
| C. | 1 |
| D. | 0.4 |
| Answer» E. | |
| 111. |
In 8 cavity magnetron the π mode corresponds to a total phase shift equal to |
| A. | ± 8 π radians around the periphery |
| B. | ± 4 π radians around the periphery |
| C. | ± 2 π radians around the periphery |
| D. | ± 16 π radians around the periphery |
| Answer» B. ± 4 π radians around the periphery | |
| 112. |
If QL is loaded Q, QE is external Q and QU is unloaded Q of a microwave resonator, then |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 113. |
Consider the following statements about directional coupler shown in the figure:1. Ports 1 and 2 are decouple2. Ports 3 and 4 are decoupled3. Pots 1 and 3 are decoupled4. Ports 1 and 4 are decoupledWhich of the above statements are correct? |
| A. | 1 and 2 only |
| B. | 3 and 4 only |
| C. | 1, 2 and 3 |
| D. | 2, 3 and 4 |
| Answer» B. 3 and 4 only | |
| 114. |
Guide wavelength (λg), cutoff wavelength (λc) and free space wavelength (λ₀) of a waveguide are related as |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 115. |
The scattering matrix of magic tee is |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 116. |
If wavelength in free space is λ₀ wavelength in insulator λ, μr is relative permittivity or insulator and ∈r is relative permittivity or insulator, then |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» C. C | |
| 117. |
In the given figure the E and H lines in a coaxial cable |
| A. | The radial lines are E lines and circular lines are H lines |
| B. | Radial lines are H lines and circular lines are E lines |
| C. | The directions of E and H lines are wrong |
| D. | Radial lines may be E and H lines depending an direction of current |
| Answer» B. Radial lines are H lines and circular lines are E lines | |
| 118. |
In a microwave coaxial line, the maximum operating frequency is f max and breakdown strength of dielectric is Ed' Then maximum power handling capacity is proportional to |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» C. C | |
| 119. |
For the strip line in the given figure the capacitance per unit length = |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |
| 120. |
At what position is the input signal inserted into a traveling-wave tube? |
| A. | At the cathode end of the helix |
| B. | At the collector |
| C. | At the collector end of the helix |
| D. | At the control grid of the electron gun |
| Answer» B. At the collector | |
| 121. |
What ferrite device can be used instead of duplexer of isolate microwave transmitter and receiver when both are connected to the same antenna? |
| A. | Isolator |
| B. | Magnetron |
| C. | Simplex |
| D. | Circulator |
| Answer» E. | |
| 122. |
In microwave transmission using digital radio, what causes most intersymbol interference? |
| A. | Delayed spreading |
| B. | Rayleigh fading |
| C. | Random Doppler shift |
| D. | Slow fading |
| Answer» B. Rayleigh fading | |
| 123. |
The resonant frequency of a cavity resonator depends upon |
| A. | The mode of operation |
| B. | Its electrical dimensions |
| C. | Its physical dimensions |
| D. | The capacitor which tunes it |
| Answer» D. The capacitor which tunes it | |
| 124. |
The highest frequency which a conventional vacuum tube oscillator can generate is not limited by the |
| A. | Electron transit time |
| B. | Distributed lead inductance |
| C. | Inter-electrode capacitance |
| D. | Degree of emission from the cathode |
| Answer» E. | |
| 125. |
To achieve good bearing resolution when using a pulsed-radar set, an important requirement is |
| A. | A narrow, antenna-beam width in the vertical plane |
| B. | A narrow, antenna-beam width in the horizontal plane |
| C. | A low repetition rate |
| D. | A high duty cycle |
| Answer» C. A low repetition rate | |
| 126. |
In an SHF pulsed radar set, a reflex klystron can be used as a |
| A. | Single mixer stage |
| B. | Local oscillator |
| C. | Transmitter oscillator |
| D. | Duplexer stage |
| Answer» C. Transmitter oscillator | |
| 127. |
Calculate the effective earth’s radius if the surface refractivity is 301. |
| A. | 8493 km |
| B. | 8493 mmi |
| C. | 6370 km |
| D. | 6370 mi |
| Answer» B. 8493 mmi | |
| 128. |
Which of the reception problems below that is not due to multipath? |
| A. | Delayed spreading |
| B. | Rayleigh fading |
| C. | Random Doppler shift |
| D. | Slow fading |
| Answer» E. | |
| 129. |
A thin layer of dirt and grime coverts the reflecting surface of the parabolic dish of a radar set. The particular effect on the performance of the radar will be |
| A. | A decrease in range |
| B. | A reduction in horizontal resolution |
| C. | No noticeable effect |
| D. | A decrease in gain |
| Answer» D. A decrease in gain | |
| 130. |
A Class-S Emergency Position-Indicating Radio Beacon (E.P.I.R.B) |
| A. | Must be capable of floating or being secured to a survival |
| B. | Must have its battery replaced after emergency use |
| C. | May be tested during the first five minutes of any hour |
| D. | All of these |
| Answer» E. | |
| 131. |
The maximum usable range of the usual radar set (on any particular range setting) is determined by |
| A. | The width of the transmitted pulses |
| B. | The interval between transmitted pulses |
| C. | The bandwidth of the receiver IF stages |
| D. | The duty cycle |
| Answer» C. The bandwidth of the receiver IF stages | |
| 132. |
Which of the following operating frequencies is used for the modern loran navigational system? |
| A. | Loran C: 100 kHz |
| B. | Loran D: 10.2 kHz |
| C. | Loran A: 1950 kHz |
| D. | Loran B: 900 kHz |
| Answer» B. Loran D: 10.2 kHz | |
| 133. |
The coarse frequency adjustment of a reflex klystron is accomplished by |
| A. | The AFC system |
| B. | Adjusting the flexible wall of the resonant cavity |
| C. | An adjustment in the synchronizer |
| D. | Varying the repeller voltage |
| Answer» C. An adjustment in the synchronizer | |
| 134. |
When used in conjunction with a radar set, the purpose of an echo box is to provide an artificial target. |
| A. | Which may be used to tune the radar synchronizer |
| B. | Which may be used to tune the radar receiver |
| C. | To the tone of the pulse repetition |
| D. | Tune the magnetron to the correct frequency |
| Answer» C. To the tone of the pulse repetition | |
| 135. |
The frequency of the oscillation generated by a magnetron, is mainly determined by |
| A. | The flux density of the external magnet |
| B. | The ratio of the dc cathode voltage to the magnetic flux density |
| C. | The number of the cavity resonators |
| D. | The dimension of each cavity resonator |
| Answer» E. | |
| 136. |
If the duration of the radar transmitted pulse, on a particular range of operation, is increased, the required bandwidth of the receiver’s IF amplifiers |
| A. | Must remain as before |
| B. | Must be increased |
| C. | May be decreased |
| D. | Must be doubled |
| Answer» D. Must be doubled | |
| 137. |
A magnetron is operated at a duty cycle of 0.001. It has a peak power output of 100 kilo-watts. Its average power is |
| A. | 10,000 watts |
| B. | 100 watts |
| C. | 1,000 watts |
| D. | 1,000,000 watts |
| Answer» C. 1,000 watts | |
| 138. |
__________ is the progressive decrease of signal strength with increasing distance. |
| A. | Radiation |
| B. | Attenuation |
| C. | Modulation |
| D. | Propagation |
| Answer» C. Modulation | |
| 139. |
Which of the following is used as an oscillator device in the SHF band? |
| A. | Thyratron tube |
| B. | Tunnel diode |
| C. | Klystron tube |
| D. | Both B and C |
| Answer» E. | |
| 140. |
Microwave frequencies are normally regarded as those in the range of |
| A. | 1 to 500 MHz |
| B. | 1000 to 10,000 GHz |
| C. | 1 to 100 GHz |
| D. | 10 to 1000 GHz |
| Answer» D. 10 to 1000 GHz | |
| 141. |
What do you call an attenuation that occurs over many different wavelengths of the carrier? |
| A. | Rayleigh fading |
| B. | Rician fading |
| C. | Wavelength fading |
| D. | Slow fading |
| Answer» E. | |
| 142. |
In a pulsed radar set, the function of the duplexer is to |
| A. | Aid in calibrating the display unit |
| B. | Prevent frequency drift in the klystron |
| C. | Allow the transmitter and the receiver to operate from a common antenna |
| D. | All of these |
| Answer» D. All of these | |
| 143. |
As the electron beam moves through a klystron’s intercavity drift space |
| A. | Frequency modulation at the input cavity creates velocity modulation at the output cavity |
| B. | Velocity modulation at the input cavity creates density modulation at the output cavity |
| C. | Density modulation at the input cavity creates velocity modulation at the output cavity |
| D. | Phase modulation at the input cavity creates velocity modulation at the output cavity. |
| Answer» C. Density modulation at the input cavity creates velocity modulation at the output cavity | |
| 144. |
The main frequency determining element of a klystron is |
| A. | The repeller voltage |
| B. | The accelerating voltage |
| C. | Its resonant cavity |
| D. | Its mode of operation |
| Answer» D. Its mode of operation | |
| 145. |
Which of the following permits a microwave signal to travel in one direction with virtually no loss, but severely attenuates any signal attempting to travel in the reverse direction? |
| A. | Isolator |
| B. | Wave trap |
| C. | Tunnel diode |
| D. | Circulator |
| Answer» B. Wave trap | |
| 146. |
Klystron oscillators are most often used in the frequency range of |
| A. | 300 to 3000 MHz |
| B. | 3000 to 30000 MHz |
| C. | 30 to 30000 MHz |
| D. | 10 to 10000 MHz |
| Answer» C. 30 to 30000 MHz | |
| 147. |
A high-power microwave pulse of the order of megawatts can be generated by a |
| A. | Traveling-wave tube |
| B. | Magnetron |
| C. | Reflex klystron |
| D. | Gunn diode |
| Answer» C. Reflex klystron | |
| 148. |
It is possible to increase the maximum range of a radar equipment by |
| A. | Lowering the pulse frequency |
| B. | Raising the peak power of the transmitter |
| C. | Narrowing the beam width and increasing the pulse duration |
| D. | All of these |
| Answer» E. | |
| 149. |
A PPI cathode-ray tube as used on a radar set |
| A. | Is used to check the percentage of modulation |
| B. | Indicates both the range and azimuth of a target |
| C. | Indicates only the range of a target |
| D. | Is used for receiver alignment |
| Answer» C. Indicates only the range of a target | |
| 150. |
Oscillators of a klystron tube are maintained |
| A. | By bunches of electrons passing the cavity grids |
| B. | By plate-to-cathode feedback |
| C. | By feedback between the accelerating grid and the repeller |
| D. | By circulating bunches of electrons within the cavities. |
| Answer» B. By plate-to-cathode feedback | |