Direction: Given question consists of two statements, one labeled as the 'Assertion (A)' and the other as 'Reason (R)'. You are to examine these two statements carefully and select the answers to these items using the codes given below.Assertion (A): The power handling capacity of a receiver antenna could be very low compared to the identical transmitting antenna.Reason (R): A transmitter antenna has to radiate a large power. The receiver antenna will have to deal only with a very small fraction of the radiated power from the transmitter.

Both A and R are individually true and R is the correct explanation of A

Both A and R are individually true but R is NOT the correct explanation of A

Directions: The item consists of two statements, one labelled as the ‘Assertion (A)’ and the other as ‘Reason (R)’.You are to examine these two statements carefully and select the answers to the item using the codes given below:Assertion (A): A Cassegrain antenna uses a main paraboloidal reflector and a relatively small hyperboloidal sub-reflector with a small horn-feed at the vertex of the main paraboloidal reflector.Reason (R): The optical technique developed by William Cassegrain was used in telescope design to obtain large magnification with a physically short telescope.This configuration is found to be effective in the design of microwave antenna also.

Both A and R individually true and R is the correct explanation of A

Both A and R are individually true but R is not the correct explanation of A

A ring of radius R carries a linear charge density λ. It is rotating with angular speed ω. The magnetic field at its center is

\(\frac{{{\mu _0}\lambda \omega }}{\pi}\)

\(\frac{{3{\mu _0}\lambda \omega }}{2}\)

\(\frac{{{\mu _0}\lambda \omega }}{2}\)

\(\frac{{{\mu _0}\lambda \omega }}{\pi}\)

An antenna located on the surface of a flat earth transmits an average power of 200 kW. Assuming that all the power is radiated uniformly over hte surface of a hemisphere with the antenna at the center, the time average Poynting vector at 50 km is

\(\frac{2}{\pi }\;{\bar a_r}W/{m^2}\)

\(\frac{2}{\pi }\;{\bar a_r}\mu \;W/{m^2}\)

Parabolic reflectors use Cassegrain feed to :

increase the gain of the system

increase the beam width of the system

reduce the size of the main reflector

allow the feed to be placed at a convenient point

An antenna behaves as a Resonant Circuit if

Its height is an integral multiple of \(\frac{{n\lambda }}{2}\)

Its length is an integral multiple of \(\frac{{n\lambda }}{2}\)

Its height is an integral multiple of \(\frac{{n\lambda }}{2}\)

Its length is even multiple of \(\frac{{n\lambda }}{2}\)

Its length is an odd multiple of \(\frac{{n\lambda }}{2}\)

For a short dipole antenna:

The current distribution along its length is uniform irrespective of the length

The radiation intensity is maximum along the normal to the dipole axis

The current distribution along its length is uniform irrespective of the length

The effective length equals its physical length

The input impedance is independent of the location of the feed – point

Radiation resistance of a Hertzian dipole of length dl is

\(80π~(\frac{dl}{\lambda})\) ohms

\(80π^2(\frac{dl}{\lambda})^2\) ohms

\(80π~(\frac{dl}{\lambda})\) ohms

\(80~(\frac{dl}{\lambda})\)ohms

\(80π~(\frac{\pi dl}{\lambda})\) ohms

A dipole with a length of 1.5 m operates at 100 MHz while the other has a length of 15 m and operates at 10 MHz. The dipoles are fed with same current. The power radiated by the two antennas will be

Shorter antenna will radiate 10 times more power than the longer antenna

The longer antenna will radiate 10 times more power than the shorter one

Both antennas radiate same power

Shorter antenna will radiate 10 times more power than the longer antenna

Longer antenna will radiate √10 times more power than the shorter antenna

An isotropic radiator is one which radiates energy

uniformly in the horizontal plane

In a three element Yagi antenna

The reflector is longer than the driven element which in turn is longer than the reflector

All the three elements are of equal length

The driven element and the director are of equal length but the reflector is longer than both of them

The reflector is longer than the driven element which in turn is longer than the director

The reflector is longer than the driven element which in turn is longer than the reflector

In an axial mode operation of a helical antenna, maximum field radiated by the antenna is:

in a plane normal to the helix axis

along the axis of the helical antenna

in a plane normal to the helix axis

in both axial and normal planes

58 + Mcqs in Antennas in Electromagnetic Theory Page 1 McqOptions

1.	A radar system uses magnetron as high-power RF source. Its transmitter emits 300kW RF power at 10% duty factor. If the efficiency of radar transmitter during pulse is 60% and the power required during pulse off period is 1kW. The average power dissipation in radar is,
A.	50.9 kW
B.	301 kW
C.	20.9 kW
D.	150.5 kW
Answer» D. 150.5 kW

Discussion

2.	A broadside array operating at 100 cm wavelength consist of 4 half wave dipoles spaced 50 cm apart.Each element carries radio frequency current in the same phase and of magnitude 0.5 A. The radiated power will be _______ if the radiation resistance is 146 ohm.
A.	146 W
B.	73 W
C.	36.5 W
D.	18.25 W
Answer» C. 36.5 W

Discussion

3.	For pulse radar with a maximum unambiguous range of 60 km, what is the maximum allowable pulse repetition frequency?
A.	5 × 105 pps
B.	2 × 104 pps
C.	4 × 105 pps
D.	2.5 × 105 pps
Answer» E.

Discussion

4.	Consider a wireless communication link between a transmitter and a receiver located in free space, with finite and strictly positive capacity. If the effective areas of the transmitter and the receiver antennas, and the distance between them are all doubled, and everything else remains unchanged, the maximum capacity of the wireless link
A.	increases by a factor of 2
B.	decreases by a factor of 2
C.	remains unchanged
D.	decreases by a factor of √2
Answer» D. decreases by a factor of √2

Discussion

5.	Direction: Given question consists of two statements, one labeled as the 'Assertion (A)' and the other as 'Reason (R)'. You are to examine these two statements carefully and select the answers to these items using the codes given below.Assertion (A): The power handling capacity of a receiver antenna could be very low compared to the identical transmitting antenna.Reason (R): A transmitter antenna has to radiate a large power. The receiver antenna will have to deal only with a very small fraction of the radiated power from the transmitter.
A.	Both A and R are individually true and R is the correct explanation of A
B.	Both A and R are individually true but R is NOT the correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» E.

Discussion

6.	Consider the following statements:The inter element spacing of1. More than \(λ\) in array antenna will produce grating lobes in unscanned condition.2. More than λ/2 but less than λ in array antenna will produce grating lobe under scanned condition.3. Less than λ/2 in array antenna will not produce any grating lobe.4. More than 1.5 λ in array antenna will not produce any grating lobe.Which of the above statements are correct?
A.	1 and 2 only
B.	3 and 4 only
C.	1, 2 and 3 only
D.	1, 2, 3 and 4
Answer» D. 1, 2, 3 and 4

Discussion

7.	A pulsed radar, operating at 3 GHz, having a pulse width of 2 μsec receives an echo from a target, 10 μsec after sending the signal. The approximate range of the target is
A.	300 m
B.	1500 m
C.	3000 m
D.	5000 m
Answer» C. 3000 m

Discussion

8.	Match List I with List II and select the correct answer using the given below the list:List IList IIA. Two isotropes half wavelength apart fed in phaseB. Two isotropes quarter wavelength apart 90° phase shift2. C. Two isotropes quarter wavelength apart fed in phase3.
A.	A - 1, B - 3, C - 2
B.	A - 2, B - 3, C- 1
C.	A - 1, B - 2, C - 3
D.	A - 2, B - 1, C - 3
Answer» C. A - 1, B - 2, C - 3

Discussion

9.	Directions: The item consists of two statements, one labelled as the ‘Assertion (A)’ and the other as ‘Reason (R)’.You are to examine these two statements carefully and select the answers to the item using the codes given below:Assertion (A): A Cassegrain antenna uses a main paraboloidal reflector and a relatively small hyperboloidal sub-reflector with a small horn-feed at the vertex of the main paraboloidal reflector.Reason (R): The optical technique developed by William Cassegrain was used in telescope design to obtain large magnification with a physically short telescope.This configuration is found to be effective in the design of microwave antenna also.
A.	Both A and R individually true and R is the correct explanation of A
B.	Both A and R are individually true but R is not the correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

10.	An axial magnetic field is applied to a cylindrical rod. The Faraday rotation of a plane-polarized beam after emergence from the rod is 5°. If both the field and length of the rod are doubled, then the angle of rotation is
A.	40°
B.	5°
C.	10°
D.	20°
Answer» E.

Discussion

11.	A vertical wire of 1 m length caries a current of 1 A at 10 MHz. The total radiated power is nearly
A.	0.43 W
B.	0.88 W
C.	7.3 W
D.	73 W
Answer» C. 7.3 W

Discussion

12.	An antenna can be modeled as an electric dipole of length 5 m at 3 MHz. Find the radiation resistance of the antenna assuming uniform current over the length.
A.	2 Ω
B.	1 Ω
C.	4 Ω
D.	0.5 Ω
Answer» B. 1 Ω

Discussion

13.	If the minimum range is to be doubled in a radar, the peak power has to be increased by a factor of
A.	4
B.	8
C.	16
D.	32
Answer» D. 32

Discussion

14.	Calculate the radiation efficiency of an antenna if the input power is 100 W and the power dissipated is 5W:
A.	0.05
B.	0.95
C.	1
D.	0.4
Answer» B. 0.95

Discussion

15.	Consider the following statements associated with microstrip patch antenna:1. The microstrip patch behaves more like a leaky cavity rather than like a radiator and this is not a highly efficient antenna.2. They can be adapted for radiation of circularly polarized waves.Which of the above statements is/are correct?
A.	1 only
B.	2 only
C.	Both 1 and 2
D.	Neither 1 nor 2
Answer» B. 2 only

Discussion

16.	A ring of radius R carries a linear charge density λ. It is rotating with angular speed ω. The magnetic field at its center is
A.	\(\frac{{3{\mu _0}\lambda \omega }}{2}\)
B.	\(\frac{{{\mu _0}\lambda \omega }}{2}\)
C.	\(\frac{{{\mu _0}\lambda \omega }}{\pi}\)
D.	μ0λω
Answer» C. \(\frac{{{\mu _0}\lambda \omega }}{\pi}\)

Discussion

17.	A parabolic reflector is designed to have a directivity of 30 dB at 300 MHz. If the aperture efficiency is 55% then the half power beamwidth is
A.	4.31°
B.	8.62°
C.	17.24°
D.	none of these
Answer» E.

Discussion

18.	A radio cab company with its antenna at a height of 15 m communicates with a cab having its antenna 1.5 m. The maximum communication distance without obstacles is roughly:
A.	10 km
B.	20 km
C.	28 km
D.	36 km
Answer» C. 28 km

Discussion

19.	An antenna located on the surface of a flat earth transmits an average power of 200 kW. Assuming that all the power is radiated uniformly over hte surface of a hemisphere with the antenna at the center, the time average Poynting vector at 50 km is
A.	Zero
B.	\(\frac{2}{\pi }\;{\bar a_r}W/{m^2}\)
C.	\(\frac{40}{\pi }\;\mu W/m^2\)
D.	\(\frac{2}{\pi }\;{\bar a_r}\mu \;W/{m^2}\)
Answer» E.

Discussion

20.	A stationary CW radar operating at 5 GHz. What is the Doppler frequency shift, if the target is moving at 108 km/hr speed?
A.	3.6 kHz
B.	1000 Hz
C.	500 Hz
D.	1800 Hz
Answer» D. 1800 Hz

Discussion

21.	A fixed radar station transmits 100 kW at 3 GHz. The smallest ocean-going ship has a radar cross-section of 200m2. The radar antenna gain is 16 dB. If detection requires a minimum of 1 nW /m2 at the radar antenna, the effective range of the radar is nearly
A.	7.1 km
B.	8.4 km
C.	70.7 km
D.	84.0 km
Answer» C. 70.7 km

Discussion

22.	Parabolic reflectors use Cassegrain feed to :
A.	increase the gain of the system
B.	increase the beam width of the system
C.	reduce the size of the main reflector
D.	allow the feed to be placed at a convenient point
Answer» E.

Discussion

23.	An antenna behaves as a Resonant Circuit if
A.	Its length is an integral multiple of \(\frac{{n\lambda }}{2}\)
B.	Its height is an integral multiple of \(\frac{{n\lambda }}{2}\)
C.	Its length is even multiple of \(\frac{{n\lambda }}{2}\)
D.	Its length is an odd multiple of \(\frac{{n\lambda }}{2}\)
Answer» B. Its height is an integral multiple of \(\frac{{n\lambda }}{2}\)

Discussion

24.	In the near field, the radiated waves take the form of:
A.	Spherical wave
B.	Plane-wave
C.	Cylindrical wave
D.	Conical wave
Answer» B. Plane-wave

Discussion

25.	Match List I with List II and select the correctanswer using the code given below the listsList IList IIA. \(\frac{d}{\lambda } = 0.25,\;\alpha = 90^\circ \)1. B. \(\frac{d}{\lambda } = 0.5,\;\alpha = 0^\circ\)2. C. \(\frac{d}{\lambda } = 0.5,\;\alpha = 180^\circ \)3. D. \(\frac{d}{\lambda } = 1.0,\;\alpha = 180^\circ \)4. Code:
A.	A - 4, B - 3, C - 1, D - 2
B.	A - 2, B - 1, C - 3, D - 4
C.	A - 4, B - 1, C - 3, D - 2
D.	A - 2, B - 3, C - 1, D - 4
Answer» E.

Discussion

26.	In a communication system, both transmitting and receiving antennas are vertically polarized. On a clear sunny day, the power received at the Receiver is 1 mW. On a rainy day due to rain-induced depolarization, the plane of polarization of the received wave gets rotated by 60° when it reaches the receiving antenna. The received power at the receiver shall be:
A.	0.5 mW
B.	0.866 mW
C.	1 mW
D.	0.25 mW
Answer» E.

Discussion

27.	Consider the following statements:If the maximum range of radar has to be doubled1. the peak transmitted power may be increased 16 folds2. the antenna diameter may be doubled3. the sensitivity of receiver may be doubledWhich of the above statements are correct?
A.	1 only
B.	2 and 3
C.	3 and 4
D.	1 and 4
Answer» B. 2 and 3

Discussion

28.	An instrument to check whether RF power in the transmission line is transferred to the antenna is:
A.	an antenna tuner
B.	a dummy load
C.	a keying monitor
D.	wave ratio meter
Answer» E.

Discussion

29.	A radar receiver has a detection SNR threshold of 10 dB for a 4 MHz bandwidth signal at 300 MHz frequency. If the transmit EIRP of the radar is 40 dBW and receive G/T is 10 dB/K, what is the minimum Radar Cross section (in dB-meter square) detectable at 10 km range?(Given: 10 log (4π) = 11, log 10 (k) = -228.6, k is Boltzmann constant)
A.	-15.6 dBm2
B.	-8.6 dBm2
C.	-9.6 dBm2
D.	-5.6 dBm2
Answer» D. -5.6 dBm2

Discussion

30.	For a short dipole antenna:
A.	The radiation intensity is maximum along the normal to the dipole axis
B.	The current distribution along its length is uniform irrespective of the length
C.	The effective length equals its physical length
D.	The input impedance is independent of the location of the feed – point
Answer» B. The current distribution along its length is uniform irrespective of the length

Discussion

31.	A Cassegrain reflector antenna has a sub-reflector whose geometrical shape is:
A.	Paraboloid
B.	Hyperboloid
C.	Ellipsoid
D.	Spherical
Answer» C. Ellipsoid

Discussion

32.	Radiation resistance of a Hertzian dipole of length dl is
A.	\(80π^2(\frac{dl}{\lambda})^2\) ohms
B.	\(80π~(\frac{dl}{\lambda})\) ohms
C.	\(80~(\frac{dl}{\lambda})\)ohms
D.	\(80π~(\frac{\pi dl}{\lambda})\) ohms
Answer» B. \(80π~(\frac{dl}{\lambda})\) ohms

Discussion

33.	If the frequency of the signal is 1 MHz, the minimum height of the transmitting antenna should be:
A.	70 m
B.	75 m
C.	50 m
D.	72.5 m
Answer» C. 50 m

Discussion

34.	A dipole with a length of 1.5 m operates at 100 MHz while the other has a length of 15 m and operates at 10 MHz. The dipoles are fed with same current. The power radiated by the two antennas will be
A.	The longer antenna will radiate 10 times more power than the shorter one
B.	Both antennas radiate same power
C.	Shorter antenna will radiate 10 times more power than the longer antenna
D.	Longer antenna will radiate √10 times more power than the shorter antenna
Answer» C. Shorter antenna will radiate 10 times more power than the longer antenna

Discussion

35.	A short current element has length l = 0.03 λ, where λ is the wavelength. The radiation resistance for uniform current distribution is
A.	0.072π2 Ω
B.	80π2 Ω
C.	72 Ω
D.	80 Ω
Answer» B. 80π2 Ω

Discussion

36.	An isotropic radiator is one which radiates energy
A.	in a well-defined direction
B.	uniformly in all directions
C.	inside a hollow space
D.	uniformly in the horizontal plane
Answer» C. inside a hollow space

Discussion

37.	If the diameter of a \(\frac{\lambda }{2}\) the dipole antenna is increased from \(\frac{\lambda }{{100}}\) to \(\frac{\lambda }{{50}},\) then its
A.	Bandwidth increases
B.	Bandwidth decreases
C.	Gain increases
D.	Gain decreases
Answer» D. Gain decreases

Discussion

38.	In a radar system if the peak transmitted power is increased by a factor of 16, and the antenna diameter is increased by a factor of two, then the maximum range will increase by a factor of
A.	16
B.	4
C.	8
D.	2
Answer» C. 8

Discussion

39.	A half-wave dipole working at 100 MHz in free space radiates a power of 1000 Watts. The field strength at a distance of 10 kms in the direction of maximum radiation is
A.	1.73 mV/m
B.	2.12 mV/m
C.	2.22 mV/m
D.	22.2 mV/m
Answer» D. 22.2 mV/m

Discussion

40.	A half wavelength dipole is kept in the x-y plane and oriented along 45° from the x-axis. Determine the direction of null in the radiation pattern for 0 ≤ Φ ≤ π. Here the angle θ (0 ≤ θ ≤ π) is measured from the z-axis, and the angle Φ (0 ≤ Φ ≤ 2π) is measured from the x-axis in the x-y plane.
A.	θ = 90°, Φ = 45°
B.	θ = 45°, Φ = 90°
C.	θ = 90°, Φ = 135°
D.	θ = 45°, Φ = 135°
Answer» B. θ = 45°, Φ = 90°

Discussion

41.	In a three element Yagi antenna
A.	All the three elements are of equal length
B.	The driven element and the director are of equal length but the reflector is longer than both of them
C.	The reflector is longer than the driven element which in turn is longer than the director
D.	The reflector is longer than the driven element which in turn is longer than the reflector
Answer» D. The reflector is longer than the driven element which in turn is longer than the reflector

Discussion

42.	Match List-I with List-II and select the correct answer using the code given below the lists:List-IList-IIA.Helical antenna1.Fan-shaped beamsB.Sect-oral horn2.Shaped beamsC.Phased arrays3.Circular polarizationD.Parabolic reflector4.Pencil beams
A.	A-3, B-1, C-2, D-4
B.	A-4, B-1, C-2, D-3
C.	A-3, B-2, C-1, D-4
D.	A-4, B-2, C-1, D-3
Answer» B. A-4, B-1, C-2, D-3

Discussion

43.	An antenna with an efficiency of 90% has a maximum radiation intensity of 0.5 W/Steradian. Calculate the directive gain of the antenna when the input power to the antenna is 0.4 W.
A.	18.23
B.	17.4
C.	11.2
D.	21.6
Answer» C. 11.2

Discussion

44.	A parabolic reflector antenna used for reception of data is 1 meter in diameter and operates at 30 GHz. The far field distance of this antenna for a quadratic phase error of 22.5 degree is:
A.	200 meter
B.	50 meter
C.	100 meter
D.	150 meter
Answer» B. 50 meter

Discussion

45.	In a radar system, if the peak transmitted power is increased by a factor of 16 and the antenna diameter is increased by a factor of 2, then the maximum range will increase by a factor of
A.	16
B.	8
C.	4
D.	\(\sqrt 8 \)
Answer» D. \(\sqrt 8 \)

Discussion

46.	In a uniform linear array, four isotropic radiating elements are spaced λ / 4 apart. The progressive phase shift between the elements required for forming the main beam at 60° of the end fire is:
A.	-π
B.	-π / 2
C.	-π / 4
D.	-π / 8
Answer» D. -π / 8

Discussion

47.	In an axial mode operation of a helical antenna, maximum field radiated by the antenna is:
A.	along the axis of the helical antenna
B.	in a plane normal to the helix axis
C.	in both axial and normal planes
D.	None of the above
Answer» B. in a plane normal to the helix axis

Discussion

48.	If the receiving antenna is polarized at 90° with respect to the transmitting antenna, it will receive
A.	No signal
B.	Minimum signal
C.	Maximum signal
D.	Same signal
Answer» B. Minimum signal

Discussion

49.	A bistatic radar system shown in figure has following parameters: f = 5 GHz, Gdt = 34 dB, Gdr = 22 dB. To obtain a return power of 8p W the minimum necessary radiated power should be
A.	1.394 kW
B.	2.046 kW
C.	1.038 kW
D.	3.46 kW
Answer» D. 3.46 kW

Discussion

50.	For an infinitesimally small dipole in free space, the electric field Eθ in the far-field is proportional to (e-jkr/r)sin θ, where k = 2π/λ. A vertical infinitesimally small electric dipole (δl ≪ λ) is placed at a distance h (h > 0) above an infinite ideal conducting plane, as shown in the figure. The minimum value of h, for which one of the maxima in the far-field radiation pattern occurs at θ = 60°, is
A.	λ
B.	0.5λ
C.	0.25λ
D.	0.75λ
Answer» B. 0.5λ

Discussion

Explore topic-wise MCQs in Electromagnetic Theory.

A radar system uses magnetron as high-power RF source. Its transmitter emits 300kW RF power at 10% duty factor. If the efficiency of radar transmitter during pulse is 60% and the power required during pulse off period is 1kW. The average power dissipation in radar is,

A broadside array operating at 100 cm wavelength consist of 4 half wave dipoles spaced 50 cm apart.Each element carries radio frequency current in the same phase and of magnitude 0.5 A. The radiated power will be _______ if the radiation resistance is 146 ohm.

For pulse radar with a maximum unambiguous range of 60 km, what is the maximum allowable pulse repetition frequency?

A pulsed radar, operating at 3 GHz, having a pulse width of 2 μsec receives an echo from a target, 10 μsec after sending the signal. The approximate range of the target is

Match List I with List II and select the correct answer using the given below the list:List IList IIA. Two isotropes half wavelength apart fed in phaseB. Two isotropes quarter wavelength apart 90° phase shift2. C. Two isotropes quarter wavelength apart fed in phase3.

An axial magnetic field is applied to a cylindrical rod. The Faraday rotation of a plane-polarized beam after emergence from the rod is 5°. If both the field and length of the rod are doubled, then the angle of rotation is

A vertical wire of 1 m length caries a current of 1 A at 10 MHz. The total radiated power is nearly

An antenna can be modeled as an electric dipole of length 5 m at 3 MHz. Find the radiation resistance of the antenna assuming uniform current over the length.

If the minimum range is to be doubled in a radar, the peak power has to be increased by a factor of

Calculate the radiation efficiency of an antenna if the input power is 100 W and the power dissipated is 5W:

A ring of radius R carries a linear charge density λ. It is rotating with angular speed ω. The magnetic field at its center is

A parabolic reflector is designed to have a directivity of 30 dB at 300 MHz. If the aperture efficiency is 55% then the half power beamwidth is

A radio cab company with its antenna at a height of 15 m communicates with a cab having its antenna 1.5 m. The maximum communication distance without obstacles is roughly:

An antenna located on the surface of a flat earth transmits an average power of 200 kW. Assuming that all the power is radiated uniformly over hte surface of a hemisphere with the antenna at the center, the time average Poynting vector at 50 km is

A stationary CW radar operating at 5 GHz. What is the Doppler frequency shift, if the target is moving at 108 km/hr speed?

A fixed radar station transmits 100 kW at 3 GHz. The smallest ocean-going ship has a radar cross-section of 200m2. The radar antenna gain is 16 dB. If detection requires a minimum of 1 nW /m2 at the radar antenna, the effective range of the radar is nearly

Parabolic reflectors use Cassegrain feed to :

An antenna behaves as a Resonant Circuit if

In the near field, the radiated waves take the form of:

Consider the following statements:If the maximum range of radar has to be doubled1. the peak transmitted power may be increased 16 folds2. the antenna diameter may be doubled3. the sensitivity of receiver may be doubledWhich of the above statements are correct?

An instrument to check whether RF power in the transmission line is transferred to the antenna is:

For a short dipole antenna:

A Cassegrain reflector antenna has a sub-reflector whose geometrical shape is:

Radiation resistance of a Hertzian dipole of length dl is

If the frequency of the signal is 1 MHz, the minimum height of the transmitting antenna should be:

A dipole with a length of 1.5 m operates at 100 MHz while the other has a length of 15 m and operates at 10 MHz. The dipoles are fed with same current. The power radiated by the two antennas will be

A short current element has length l = 0.03 λ, where λ is the wavelength. The radiation resistance for uniform current distribution is

An isotropic radiator is one which radiates energy

If the diameter of a \(\frac{\lambda }{2}\) the dipole antenna is increased from \(\frac{\lambda }{{100}}\) to \(\frac{\lambda }{{50}},\) then its

In a radar system if the peak transmitted power is increased by a factor of 16, and the antenna diameter is increased by a factor of two, then the maximum range will increase by a factor of

A half-wave dipole working at 100 MHz in free space radiates a power of 1000 Watts. The field strength at a distance of 10 kms in the direction of maximum radiation is

In a three element Yagi antenna

Match List-I with List-II and select the correct answer using the code given below the lists:List-IList-IIA.Helical antenna1.Fan-shaped beamsB.Sect-oral horn2.Shaped beamsC.Phased arrays3.Circular polarizationD.Parabolic reflector4.Pencil beams

An antenna with an efficiency of 90% has a maximum radiation intensity of 0.5 W/Steradian. Calculate the directive gain of the antenna when the input power to the antenna is 0.4 W.

A parabolic reflector antenna used for reception of data is 1 meter in diameter and operates at 30 GHz. The far field distance of this antenna for a quadratic phase error of 22.5 degree is:

In a radar system, if the peak transmitted power is increased by a factor of 16 and the antenna diameter is increased by a factor of 2, then the maximum range will increase by a factor of

In a uniform linear array, four isotropic radiating elements are spaced λ / 4 apart. The progressive phase shift between the elements required for forming the main beam at 60° of the end fire is:

In an axial mode operation of a helical antenna, maximum field radiated by the antenna is:

If the receiving antenna is polarized at 90° with respect to the transmitting antenna, it will receive

A bistatic radar system shown in figure has following parameters: f = 5 GHz, Gdt = 34 dB, Gdr = 22 dB. To obtain a return power of 8p W the minimum necessary radiated power should be