MCQOPTIONS
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MCQOPTIONS
This section includes 1085 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.
| 801. |
The polarization phenomena in Faraday rotation |
| A. | is non-reciprocal |
| B. | exists along perpendicular direction |
| C. | exists along the axis of array |
| D. | does not exist |
| Answer» B. exists along perpendicular direction | |
| 802. |
Maximum effective aperture of an antenna which is operating at a wavelength of 3 meters and has a directivity of 100 |
| A. | 71.68 m2 |
| B. | 716 m2 |
| C. | 7.16 m2 |
| D. | 71.6 m2 |
| Answer» E. | |
| 803. |
A transmission line having 50 Ω impedance is terminated in a load of (40 + j 30) Ω. The VSWR is |
| A. | j 0.033 |
| B. | 0.8.+ j 0.6 |
| C. | 1 |
| D. | 2 |
| Answer» E. | |
| 804. |
A higher directivity is specified by |
| A. | high gain low BW (Beamwidth) |
| B. | high gain high BW |
| C. | low gain high BW |
| D. | none of the above |
| Answer» B. high gain high BW | |
| 805. |
The waveguides compared to equivalent transmission lines at low frequency are |
| A. | able to carry more power |
| B. | less noisy |
| C. | having lower attenuation |
| D. | all of the above |
| Answer» E. | |
| 806. |
Dish antennas are |
| A. | loop |
| B. | helical |
| C. | parabolic |
| D. | conical |
| Answer» D. conical | |
| 807. |
The directivity of 20 turn helix having a = 12° circumference equal to one wavelength, will be |
| A. | 1.8 dB |
| B. | 6 dB |
| C. | 12 dB |
| D. | 18 dB |
| Answer» E. | |
| 808. |
Which of the antenna is best excited by a waveguide? |
| A. | Horn |
| B. | Discone |
| C. | Helical |
| D. | Biconical |
| Answer» B. Discone | |
| 809. |
The attenuation in waveguides near the cut off frequency is |
| A. | very low |
| B. | very high |
| C. | medium |
| D. | zero |
| Answer» C. medium | |
| 810. |
__________ will have the least value of relative permeability. |
| A. | Palladium |
| B. | Silver |
| C. | Cobalt |
| D. | Iron |
| Answer» C. Cobalt | |
| 811. |
A transmission line has characteristics impedance of (75 + j 0.01) Ω and is terminated in a load impedance of (70 + j 50) Ω. The reflection coefficient will be |
| A. | 0.08 + j 0.32 |
| B. | 0.32 + j 1.38 |
| C. | 0.70 - j 2.97 |
| D. | 1.1 + j 0.32 |
| Answer» B. 0.32 + j 1.38 | |
| 812. |
Which of following antenna produces elliptical polarisation? |
| A. | Helical |
| B. | Parabolic |
| C. | Dipole |
| D. | None |
| Answer» E. | |
| 813. |
The maximum usable frequency for the 'E' layer is 10 MHz. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 814. |
In an impedance smith chart, a clockwise movement along a constant resistance circle gives rise to |
| A. | decrease in the value of reactance |
| B. | an increase in the value of reactance |
| C. | no change in the reactance value |
| D. | no change in the impedance value |
| Answer» C. no change in the reactance value | |
| 815. |
In a loss-less transmission line |
| A. | R << ω L; G << ω C |
| B. | R = ω L, G = ω C |
| C. | R >> ω L; G >> ω C |
| D. | none of the above |
| Answer» B. R = œâ L, G = œâ C | |
| 816. |
The term critical frequency denotes |
| A. | the lowest frequency that is reflected by the ionosphere |
| B. | the highest frequency that is reflected by the ionosphere at vertical distance |
| C. | the lowest frequency by which communication is possible between two given points |
| D. | none of the above |
| Answer» C. the lowest frequency by which communication is possible between two given points | |
| 817. |
The I/P impedance of a short circuited quarter wave long transmission line is |
| A. | purely reactive |
| B. | purely resistive |
| C. | depend on the characteristic impedance of the line |
| D. | none of the above |
| Answer» E. | |
| 818. |
High frequency waves are |
| A. | absorbed by the F2 layer |
| B. | reflected by the D layer |
| C. | affected by the solar cycle |
| D. | none of the above |
| Answer» D. none of the above | |
| 819. |
For static magnetic field Maxwell's curl equation is given by |
| A. | ∇ . = μ0 |
| B. | ‚àá x = 0 |
| C. | ∇ x = μ0 |
| D. | ∇ x = μ0/ |
| Answer» D. ‚àá x = Œº0/ | |
| 820. |
What will be the propagation constant at 10 MHz? |
| A. | 3.4 radians/km |
| B. | 34.4 radians/km |
| C. | 344 radians/km |
| D. | 3440 radians/km |
| Answer» D. 3440 radians/km | |
| 821. |
An antenna has 40 Ω resistance and 60 Ω radiation resistance. The efficiency of the antenna is |
| A. | 0.3 |
| B. | 0.4 |
| C. | 0.5 |
| D. | 0.6 |
| Answer» E. | |
| 822. |
The affect of ground on radiation pattern is to |
| A. | cause cancellation of radiation along the ground |
| B. | produce more number of nulls |
| C. | both (a) and (b) |
| D. | either (a) or (b) |
| Answer» D. either (a) or (b) | |
| 823. |
A higher value of Standing Wave Ratio indicates |
| A. | least mismatch between line and load |
| B. | greater mismatch between load and line |
| C. | number of nodes is equal to the number of antinodes |
| D. | none of the above |
| Answer» C. number of nodes is equal to the number of antinodes | |
| 824. |
The skip distance is |
| A. | same for each layer |
| B. | independent of frequency |
| C. | independent of the state of ionisation |
| D. | independent of transmitted power |
| Answer» E. | |
| 825. |
So-called 'grounded' antennas are often found insulated from the ground electrically. |
| A. | 1 |
| B. | |
| Answer» B. | |
| 826. |
Which of the following relations is correct? |
| A. | ‚àá . = r |
| B. | ‚àá . = r |
| C. | ‚àá . = - r |
| D. | ‚àá . = |
| Answer» C. ‚àá . = - r | |
| 827. |
For VLF antennas radiation resistance is usually of the order of |
| A. | less than one ohm |
| B. | 13 to 20 ohms |
| C. | around 100 ohms |
| D. | more than 200 ohms |
| Answer» B. 13 to 20 ohms | |
| 828. |
In an home T.V. receiver, the leed in from the antenna is |
| A. | coaxial cable of 75 Ω |
| B. | ordinary twisted wire |
| C. | bar copper wire |
| D. | twin wire |
| Answer» E. | |
| 829. |
When the magnetic vector is parallel to the boundary surface and electric vector is parallel to the place of incidence, the polarization is |
| A. | zero |
| B. | vertical |
| C. | perpendicular |
| D. | horizontal |
| Answer» C. perpendicular | |
| 830. |
The gain of a current element is |
| A. | 0 dB |
| B. | 1.67 dB |
| C. | 1.76 dB |
| D. | 3 dB |
| Answer» D. 3 dB | |
| 831. |
For space propagation, what will be the electric field strength at receiving antenna |
| A. | |
| B. | 30 WTGT |
| Answer» B. 30 WTGT | |
| 832. |
The incidence from dielectric medium 1 (ε1) into dielectric medium 2 (ε2), Brewster angle θB and the corresponding angle of transmission θt for will be respectively |
| A. | 30° and 30° |
| B. | 30° and 60° |
| C. | 60° and 30° |
| D. | 30° and 60° |
| Answer» D. 30¬∞ and 60¬∞ | |
| 833. |
Which type of fading causes serious distortion of modulated signal? |
| A. | Selective fading |
| B. | Interference fading |
| C. | Absorption fading |
| D. | Polarization fading |
| Answer» B. Interference fading | |
| 834. |
A loop antenna is a commonly used for |
| A. | radar |
| B. | direction finding |
| C. | satellite communication |
| D. | all of the above |
| Answer» C. satellite communication | |
| 835. |
The input impedance for a half dipole if radii of both the antenna is 4 and 8 meter respectively |
| A. | 600 Ω |
| B. | 100 Ω |
| C. | 657 Ω |
| D. | 650 Ω |
| Answer» D. 650 Œ© | |
| 836. |
For infinite value of SWR on a transmission line, the line be terminated with impedance as |
| A. | an open-circuit |
| B. | a short-circuit |
| C. | a pure resistance |
| D. | all of the above |
| Answer» E. | |
| 837. |
The unit of ‚àá x H is |
| A. | Ampere |
| B. | Ampere/meter |
| C. | Ampere/m2 |
| D. | Ampere-meter |
| Answer» D. Ampere-meter | |
| 838. |
A time varying magnetic field produces |
| A. | electric field only |
| B. | magnetic field only |
| C. | both magnetic and electric fields |
| D. | none of the above |
| Answer» D. none of the above | |
| 839. |
A lossless transmission line is connected to two identical voltage source as shown in figure. The impedance measured at the midpoint AA' is |
| A. | ‚àû |
| B. | 100 |
| C. | 50 |
| D. | 25 |
| Answer» B. 100 | |
| 840. |
Magnesium is alloyed with conducting materials for antenna primarily with the purpose of |
| A. | increasing efficiency |
| B. | improving radiative power |
| C. | reducing weight |
| D. | increasing density |
| Answer» D. increasing density | |
| 841. |
Which one of following is correct for broadside array? |
| A. | Direction of radiation is perpendicular to axis |
| B. | Also perpendicular to the plane |
| C. | Current is fed of equal amplitude equal phase |
| D. | All |
| Answer» E. | |
| 842. |
The attenuation in waveguide above to cut off frequency |
| A. | very high |
| B. | very low |
| C. | zero |
| D. | infinite |
| Answer» C. zero | |
| 843. |
Brewster angle is the angle for which there is |
| A. | no reflection and the incident wave is vertically polarized |
| B. | reflection and the incident wave is horizontally polarized |
| C. | no reflection and the incident wave is horizontally polarized |
| D. | none of the above |
| Answer» B. reflection and the incident wave is horizontally polarized | |
| 844. |
A loss less transmission line is terminated in a load which reflects a part of the incident power. The measured VSWR is 2. The percentage of the power that is reflected back is |
| A. | 57.73 |
| B. | 33.33 |
| C. | 0.11 |
| D. | 11.11 |
| Answer» E. | |
| 845. |
The ratio of the directivity of an end fire antenna to that of a broadside antenna is |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 5 |
| Answer» B. 3 | |
| 846. |
The value of VSWR is taken as ‚àû when the line is |
| A. | short-circuited |
| B. | open-circuited |
| C. | terminated with full load |
| D. | terminated with load equal to the characteristic impedance of the load |
| Answer» C. terminated with full load | |
| 847. |
SHF range is |
| A. | 30 - 300 MHz |
| B. | 300 - 3000 MHz |
| C. | 3000 - 30000 MHz |
| D. | 30000 - 300000 MHz |
| Answer» D. 30000 - 300000 MHz | |
| 848. |
Which of the following statements is incorrect regarding Balun transformer? |
| A. | It changes impedance like current transformer |
| B. | It changes balanced to unbalanced line |
| C. | It is used to couple a co-axial line to a parallel line wire |
| D. | Any of the above |
| Answer» B. It changes balanced to unbalanced line | |
| 849. |
A parabolic antenna produces a radiation pattern which is |
| A. | circularly polarized |
| B. | highly directional |
| C. | omnidirectional |
| D. | linearly polarized |
| Answer» C. omnidirectional | |
| 850. |
Radiowaves are electromagnetic waves having frequency range |
| A. | 0.001 to 50 H |
| B. | 0.001 to 50 kHz |
| C. | 0.002 to 50 MHz |
| D. | 0.001 to 1016 Hz |
| Answer» E. | |