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.
| 1. |
Distilled water at 25°C is characterized by σ = 1.7 x 10 mho/m and ε = 78 ε at a frequency of 3 GHz. Its loss tangent is (ε = 10/36 F/m) |
| Answer» Loss tangent . | |
| 2. |
The input impedance of short-circuited line of length where < λ/4 |
| Answer» l < λ/4, ZL = 0 , if Zd comes +j kZC then inductive, If Zd comes -j kZC then capacitive. For 0 ≤ l ≤ 1/4, λ ≤ l ≤ 3λ/4 will be inductive. | |
| 3. |
If the height of transmitting and receiving antenna in a LOS system are 49 meter and a 9 meter respectively then the distance up to which communication may be possible is about |
| Answer» Distance = 0.4 [ht + hr] metre. | |
| 4. |
A material has conductivity of 10 mho/m and a relative permittivity of 4. The frequency at which conduction current in the medium is equal to displacement current is |
| Answer» Conduction current density J = wD J = σE σE = ωD = 2p fD | |
| 5. |
An end fire array consisting of several half-wave lengths of directive gain 40, then find the width of major lobe |
| Answer» . | |
| 6. |
In a line VSWR of a load is 6 dB. The reflection coefficient will be |
| Answer» VSWR = 100.6 | |
| 7. |
The refractive index of E layer at frequency of |
| Answer» | |
| 8. |
Calculate the directivity of a given linear end fire, uniform array of 20 element, each separated by λ/3 |
| Answer» . | |
| 9. |
For a 400 kHz transmission line having L = 0.5 mH/km, C = 0.08 mF and negligible R and G, the velocity propagation will be |
| Answer» m/sec. | |
| 10. |
Antenna efficiency of antenna is, if radiation resistance is 370 Ω and loss resistance is 100 Ω |
| Answer» . | |
| 11. |
At a particular time it is observed that the frequencies of F layer at Delhi is 3 MHz the maximum electron density is |
| Answer» fc = 9Nmax 3 x 106 = 9Nmax Nmax = 0.11 x 1012 11 x 1010/m3. | |
| 12. |
The effective length of an λ/2 antenna (Given R = 73 Ω and (A) = 0.13 λ and η = 120 is __________ . |
| Answer» . | |
| 13. |
Calculate cut off frequency for dominant mode in rectangular waveguide if dimensions are = 2, = 1 cm. |
| Answer» 7.5 x 109 Hz 7.5 GHz. | |
| 14. |
The input impedance for a half dipole if radii of both the antenna is 4 and 8 meter respectively |
| Answer» 657 Ω. | |
| 15. |
A rectangular waveguide measures 3 x 4.5 cm internally and has a 10 GHz signal propagated in it. Calculate the guide wavelength for dominant mode. |
| Answer» . | |
| 16. |
A rectangular waveguide measures 3 x 4.5 cm internally and has a 10 GHz signal propagated in it. Calculate the cut off frequency for dominant mode. |
| Answer» . | |
| 17. |
Find the flux crossing the plane surface defined by 0.5 ≤ ≤ 3.5 m and 0 ≤ ≤ 3 m. if |
| Answer» . | |
| 18. |
Gain of an antenna with a circular aperture of diameter 4 meter at frequency of 10 GHz, with directivity 60 |
| Answer» | |
| 19. |
If the electric field intensity is given by , the potential difference between (2, 0, 0) and (1, 2, 3) is |
| Answer» | |
| 20. |
Medium 1 has the electrical permittivity ε = 1.5 ε farad/m and occupies the region to the left of = 0 plane. Medium 2 has the electrical permittivity ε = 2.5 ε farad/m and the occupies the region to the right of = 0 plane. If E in medium 1 is volt/m, then E in medium 2 is |
| Answer» According to boundary condition hence, Ez1 = Ez2 Ey2 = Ey1 Et1 = Et2 | |
| 21. |
Polarization of a wave is |
| Answer» Direction of electric field is to be taken as reference. | |
| 22. |
Calculate the critical frequency for the E layer if maximum ionic densities are 3 x 10 |
| Answer» fc = 9Nmax 15.58 x 103 Hz. | |
| 23. |
An isolated sphere in air has a radius equal to meter, its capacitance is |
| Answer» C = 4p ε0 . R. | |
| 24. |
Find cut off wavelength for mode TE in a circular waveguide having radius 2 cm. Assume K' = 1.841 |
| Answer» . | |
| 25. |
The refractive index of E layer, if angle of incidence is 30° |
| Answer» μ = sin i | |
| 26. |
The sinusoidally time varying vector field is |
| Answer» 60° phase, same magnitude, it form. | |
| 27. |
A transmission line having 50 Ω impedance is terminated in a load of (40 + 30) Ω. The VSWR is |
| Answer» ZC = 50 Ω, ZL = 40 + J30, r . | |
| 28. |
A broadside array consisting of 200 cm wavelength with 10 half-wave dipole spacing 10 cm. And if each array element feeding with 1 amp. current and operating at same frequency then find the radiated power |
| Answer» Prad = n I2 . Rr 10 x 73 x 1 730 watt. | |
| 29. |
For static magnetic field Maxwell's curl equation is given by |
| Answer» For static field, time varying factor will be zero, ∇ x H . | |
| 30. |
For a reflection co-efficient of 0.5, the value of SWR is |
| Answer» . | |
| 31. |
If and the time average Poynting vector is |
| Answer» | |
| 32. |
Calculate the wave number in waveguide having dimensions 4 x 2 cm at 3 GHz |
| Answer» . | |
| 33. |
For a transmission line with homogeneous dielectric the capacitance per unit length is '', the relative permittivity of the dielectric is 'ε' and velocity of light in free space is '' the characteristic impedance is equal to |
| Answer» . | |
| 34. |
The I/P impedance of a short circuited quarter wave long transmission line is |
| Answer» Because for irrotational, ∇ x = 0. | |
| 35. |
A dipole antenna of λ/8 length has an equivalent total loss resistance of 1.5 Ω. The efficiency of the antenna is |
| Answer» Rr = 80p2 , Re = 1.5 Ω, . | |
| 36. |
A vertical wire of 1 meter length carries a current of 1 A at 10 MHz. The total radiated power is nearly |
| Answer» P = I2 . R (1)2 . 73 73 watt. Here, vertical wire will be considered as dipole. | |
| 37. |
The length of half-wave antenna is at 30 MHz |
| Answer» . | |
| 38. |
For a 400 kHz transmission line having L = 0.5 mH/km, C = 0.08 mF and negligible R and G, the characteristic impedance will be |
| Answer» f = 400 kHz, L = 0.5 mH, C = 0.08 mF . | |
| 39. |
Beamwidth (between first nulls) will be for an antenna at 3 MHz with directivity of 100 |
| Answer» . | |
| 40. |
The value of VSWR is taken as ∞ when the line is |
| Answer» For VSWR = ∞ , reflection coefficient must be 1 VSWR if t = 1 VSWR = ∞ for t = 1, ZL = ∞ . | |
| 41. |
The ratio of the directivity of an end fire antenna to that of a broadside antenna is |
| Answer» In Broadside, D = 2n In End fire D = 4n. | |
| 42. |
If the electric field intensity associated with a uniform plane electromagnetic wave travelling in a perfect dielectric medium is given by E(, ) = 10 cos (2 x 10 - 0.1 ) volt/metre, then the velocity of the travelling wave is |
| Answer» E(z, t) = 10 cos (2p x 107t - 0.1 pz) f = 107 Hz, β = 0.1p | |
| 43. |
An end fire array consisting of several half-wave lengths of directive gain 40, then Find width of major lobe for broadside |
| Answer» . | |
| 44. |
A uniform plane wave travelling in air is incident on the plane boundary between air and another dielectric medium with ε = 4. The reflection coefficient for the normal incidence is |
| Answer» Reflection coefficient . | |
| 45. |
A transmission line has characteristics impedance of (75 + 0.01) Ω and is terminated in a load impedance of (70 + 50) Ω. The transmission coefficient will be |
| Answer» Transmission coefficient . | |
| 46. |
Maximum effective aperture of an antenna which is operating at a wavelength of 3 meters and has a directivity of 100 |
| Answer» . | |
| 47. |
The distance between maxima and minima of a standing wave is |
| Answer» | |
| 48. |
A TV. transmitting aerial is fixed on top of a 150 metre tower located on a mountain 1200 m height. The range of transmitter is |
| Answer» 1 = 1.44[ht + ht] | |
| 49. |
A line of characteristic impedance ohms, phase velocity V = 2 x 10 m/sec and length = 2 m is terminated by a load impedance Ohms. The reflection coefficients at the input end and load end are respectively for a frequency of 50 MHz will be |
| Answer» ri . | |
| 50. |
The I/P impedance of a long short circuited section of a loss less transmission line is |
| Answer» if Zi = -jkZ0 then capacitive = jkZ0 the inductive. | |