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## [MCQ]Antenna and Radio Wave Propagation

#### Module 1

1. The axis of back lobe makes an angle of 180° with respect to the beam of an antenna.
a) True
b) False
Explanation: The axis of back lobe is opposite to the main lobe. So it makes 180° with beam of antenna. It is also a side lobe which is at 180 to main lobe.

2.Radiation resistance of a half-wave dipole is ______
a) 36.56Ω
b) 18.28Ω
c) 73.12Ω
d) 40.24Ω
Explanation: Since radiation resistance of quarter-wave monopole (l=λ/4) is 36.56Ω, then for a half-wave dipole (l=λ/2) it is given by 36.56×2 = 73.12Ω. Hertzian dipole is an ideal dipole of infinitesimal dipole.

3. Equivalent circuit representation of an antenna is ______
a) Series R, L, C
b) Parallel R, L, C
c) Series R, L parallel to C
d) Parallel R, C series to L
Explanation: Antenna is represented by a series R, L, C equivalent circuit. Antenna is used for impedance matching and acts like a transducer.

4. The equivalent area when multiplied by the instant power density which leads to free radiation of power at antenna is called as _______
a) Loss area
b) Scattering area
c) Captured area
d) Effective area
Explanation: Scattering area is the equivalent area when multiplied by the instant power density which leads to free radiation of power. Loss area leads to power dissipation and captured area leads to total power collection by the antenna. The relation among them is given by,
Captured area= effective area + loss area + scattering area.

5. A linear antenna having length less than λ/8 is called as _______
a) Short monopole
b) Short dipole
c) Half-wave dipole
d) Quarter-wave monopole
Explanation: Short monopoles have length less than λ/8 and the current distribution is triangular. Short dipole has length less than λ/2. Half-wave dipoles have length equal to λ/2. Quarter-wave monopoles have length equal to λ/4.

6. Find the power radiated by an antenna whose radiation resistance is 100Ω and operating with 3A of current at 2GHz frequency?
a) 900W
b) 1800W
c) 450W
d) 700W

7. Which of the following field varies inversely with r2?
a) Far field
b) Near field
d) Electrostatic field
Explanation: Induction field is also known as ‘Near field’, varies inversely with r2. Electrostatic field varies inversely with r3. Far field is also known as Radiation field, varies inversely with r.

8. Which of the following option is false?
a) Omni-directional antenna is a special case of directional antenna
b) Directional antenna radiates power effectively in particular directions compared to other directions
c) Isotropic antenna radiates power in all directions
d) End-fire array antenna has its main beam normal to the axis containing antenna
Explanation: End-fire array has its main beam parallel to the axis of antenna (θ=0° or 180°). For broadside antenna it is normal to the axis of antenna. Omni-directional antenna radiates power in only one direction and is non-radiating in other directions. So it is a special case of directional antenna.

9. The angular distance between two successive nulls of main lobe is called as ______
a) FNBW
b) HPBW
c) Beam width
d) FBR
Explanation: The angular distance between two successive nulls of main lobe is called First Null Beam width. Half-power beam width is the angular distance when 50% of power is radiated. FBR is the Front-to-Back ratio defined as ratio of power radiated at 0° to power radiated at 180°.

10. The receiving antenna is designed to have ____ side-lobe-ratio and ____ SNR.
a) Low, high
b) High, high
c) Low, low
d) High, low
Explanation: Side lobe ratio is ratio of power density in side lobes to main lobe. A receiving antenna is said to be efficient if side lobes are minimized and receives most of the transmitted signal. So it should have low SLR and high SNR.

11. For an isotropic antenna, the average power Pav can be expressed in terms of radiated power Pr as ____
a) Pav=Pr/4π
b) Pav=Pr/2πr2
c) Pav=Pr/2π
d) Pav=Pr/4πr2
Explanation: Average power is the total power radiated in the unit area. Here for isotropic radiation, area is spherical (say with radius r) and the area is 4πr2.
∴ Pav=Pr/4πr2

12. The Directive gain is ______ on input power to antenna and _____ on power due to ohmic losses.
a) Independent, independent
b) Dependent, independent
c) Independent, dependent
d) Dependent, dependent
Explanation: Directive gain is the ratio of power density to the average power radiated. Gd=Pd(θ,∅)Pavg So, the Directive gain is independent on both input power to antenna and power due to ohmic losses.
Power gain is dependent on input power and ohmic losses to antenna.

13. For a lossless antenna, maximum Power gain equals to the maximum directive gain.
a) True
b) False
Explanation: For a lossless antenna, ohmic losses will be zero. So, radiation efficiency will be 100%. Hence, maximum power gain will be equal to the maximum directive gain of antenna.

14. The ratio of power radiated in a particular direction to the total input power of antenna is called as _____
a) Directive gain
b) Power gain
c) Directivity
d) Partial directivity 15. Which of the following expression is correct for radiation efficiency?  16. Free space loss factor is given by _____  17. Which of the following is the Friss transmission equation for the matched polarization of antennas?  18. Let’s assume a transmitting antenna having gain 10dB is placed at a distance of 100m from the receiving antenna and radiates a power of 5W. Find the gain of the receiving antenna in dB when the received power is 150μW and transmitter frequency 500MHz?
a) 1.31dB
b) 1.19dB
c) 11.19dB
d) 13.16dB 19. Assume two similar antennas for transmitting and receiving. If the operating frequency gets reduced by 3 times then the received power gets _______
a) increases by factor 3
b) decreases by factor 3
c) increases by factor 9
d) decreases by factor 9 20. The relation between vector magnetic potential and current density is given by ______
a) ∇.A=J
b) ∇×A=H
c) ∇2 A=-μJ
d) ∇2 A=∇×H

Explanation: Magnetic Flux density B is expressed as B=∇×A
Taking curl on both sides, we get ∇×B=∇×(∇×A ) = ( ∇.A)∇-(∇.∇)A
From Maxwell’s equation, ∇.B=0 =>∇.A=0
⇨ ∇×B= -∇2 A and B= μH , ∇×H=J
⇨ ∇×μH= -∇2A
⇨ ∇2 A=-μJ.

21. The induction and radiation fields are equal at a distance of _______
a) λ/4
b) λ/6
c) λ/8
d) λ/2

Explanation: For an Hertzian dipole, equating the magnitudes of maximum induction and radiation fields we get,
Imdl4πϵ(ωv2r)=Imdl4πϵ(1r2v)
r=vω=λf2πf=λ6.

22. The ratio of radiation intensity in a given direction from antenna to the radiation intensity over all directions is called as ________
a) Directivity
c) Gain of antenna
d) Array Factor

Explanation: Directivity of antenna is defined as the ratio of radiation intensity in a given direction from antenna to the radiation intensity over all directions. D=UmaxU0.
Gain of antenna is ratio of radiation intensity in given direction to the radiation intensity of isotropic radiation. Array factor is a function of geometry of array and the excitation phase.

23. What is the overall efficiency of a lossless antenna with reflection coefficient 0.15?
a) 0.997
b) 0.779
c) 0.669
d) 0.977

Explanation: For a lossless antenna, the radiation efficiency ecd=1.
Overall efficiency of antenna is given by eo =ecd (1-γ2)=1×(1-(0.152))=0.977.

#### Module 2

1. A dipole antenna is also called as?
a) Marconi antenna
b) Yagi antenna
c) Bidirectional antenna
d) Hertz antenna
Explanation: One of the most widely used antenna types is the half-wave dipole antenna. This antenna is also formally known as the Hertz antenna after Heinrich Hertz, who first demonstrated the existence of electromagnetic waves.

2. The impedance at the center of the antenna is known as?
a) Characteristic impedance
c) Transmission impedance
d) Recovery resistance
Explanation: The transmission line is connected at the center. The dipole has an impedance of 73 V at its center, which is the radiation resistance. At the resonant frequency, the antenna appears to be a pure resistance of 73 V.

3. What happens when the radiation resistance of the antenna matches the characteristic impedance of the transmission line?
a) No transmission occurs
b) No reception occurs
c) SWR is maximum
d) SWR is minimum
Explanation: When the radiation resistance of the antenna matches the characteristic impedance of the transmission line, the SWR is minimum and maximum power reaches the antenna. This allows maximum power to be transmitted.

4. The type of dipole antenna that has a higher band width is called as?
a) Conical antenna
b) Yagi antenna
c) Helical antenna
d) Marconi antenna
Explanation: A common way to increase bandwidth in the antenna is to use a version of the dipole antenna known as the conical antenna. The overall length of the antenna is 0.73λ or 0.73(984)/f = 718.32/f. This is longer than the traditional one-half wavelength of a dipole antenna, but the physical shape changes the necessary dimensions for resonance.

5. The radiation pattern of a half-wave dipole has the shape of a ______
a) Doughnut
b) Sphere
c) Hemisphere
d) Circular
Explanation: The radiation pattern of any antenna is the shape of the electromagnetic energy radiated from or received by that antenna. Typically that radiation is concentrated in a pattern that has a recognizable geometric shape. The radiation pattern of a half-wave dipole has the shape of a doughnut.

6. What is the beam width for a half wave dipole antenna?
a) 90°
b) 180°
c) 50°
d) 250°
Explanation: The beam width is measured between the points on the radiation curve that are 3 dB down from the maximum amplitude of the curve. The maximum amplitude of the pattern occurs at 0° and 180°. The 3-dB down points are 70.7 percent of the maximum. The angle formed with two lines extending from the center of the curve to these 3-dB points is the beam width. The beam width is 90°. The smaller the beam width angle, the more directional the antenna.

7. What does the beam width of an antenna tell us?
a) Signal strength
b) Signal power
c) Directivity
Explanation: The measure of an antenna’s directivity is beam width, the angle of the radiation pattern over which a transmitter’s energy is directed or received. Beam width is measured on an antenna’s radiation pattern.

8. What is the power radiated by the antenna with gain called as?
a) Critical power
b) Transverse power
d) Transmitted power
Explanation: The power radiated by an antenna with directivity and therefore gain is called the effective radiated power (ERP). The ERP is calculated by multiplying the transmitter power fed to the antenna Pt by the power gain Ap of the antenna.

a) Doughnut
b) Sphere
c) Hemisphere
d) Circular
Explanation: An isotropic radiator is a theoretical point source of electromagnetic energy. The E and H fields radiate out in all directions from the point source, and at any given distance from the point source, the fields form a sphere.

10. What is the impedance of the folded dipole antenna?
a) 50Ω
b) 100Ω
c) 300Ω
d) 20Ω
Explanation: A popular variation of the half-wave dipole is the folded dipole. Like the standard dipole, it is one-half wavelength long. However, it consists of two parallel conductors connected at the ends with one side open at the center for connection to the transmission line. The impedance of this popular antenna is 300 V, making it an excellent match for the widely available 300-V twin lead.

11. Which of the following antennas produce a vertical radiation pattern?
a) Dipole antenna
b) Yagi antenna
c) Marconi antenna
d) Hertz antenna
Explanation: The same effect as dipole antenna can be achieved with a one-quarter wavelength antenna or Marconi antenna. A vertical dipole with the doughnut-shaped radiation pattern, in which one-half of the pattern is below the surface of the earth. This is called a vertical radiation pattern.

12. Which of the following statement is not correct?
a) Folded dipole antenna has less impedance than half dipole
b) Folded dipole is a balanced antenna
c) Folded dipole antenna is a dipole antenna with its end folded back forming a loop
d) Balun is used at the feeder when unbalanced feed is used in the folded dipole
Explanation: The impedance of folded dipole is four times the impedance of the half dipole. So its impedance is higher than the half dipole. Since folded dipole is a balanced antenna we use a balanced feeder so Balun is used.

13. Folded dipole antenna belongs to which type of antenna?
a) Reflector
b) Aperture
c) Lens
d) Wire
Explanation: Folded dipole antenna belongs to wire antenna. It is a dipole antenna with two ends folded back and connected to each other forming a loop.

14. What is the input impedance of a half wave folded dipole?
a) 73Ω
b) 292Ω
c) 146Ω
d) 36.5Ω
Explanation: The input impedance of a half wave folded dipole is four times the half wave dipole.
So Z= 4×73=292Ω

15. A half wave folded dipole of 3 wires has the impedance _____Ω.
a) 675
b) 657
c) 219
d) 292
Explanation: For a half wave folded dipole of 3 wires the impedance = n2×73=9×73=657

16. In which of the following type of folded dipole the number of conductors is varied?
a) Multi conductor folded dipole
b) Unequal conductor folded dipole
c) Both multi conductor and unequal conductor
d) Neither multi conductor nor unequal conductor
Explanation: In Multi conductor folded dipole, the two or more conductors are connected together. This increases the impedance and also the bandwidth.

17. For a multi conductor folded dipole with n conductors, the impedance is ____ Ω.
a) 2n Z
b) nZ
c) n2Z
d) Z/n
Explanation: For a multi conductor folded dipole with n conductors, the impedance is n2Z.
Where value of radiation resistance Z depends on the length of the dipole used.

18. Which of the following causes the shortening effect on multi conductor folded dipole?
a) Only thickness of conductors
b) Space between conductors
c) Radiation resistance of the dipole
Explanation: The shortening effect on the multi conductors depends on the thickness of the conductor whereas in wires it depends on the length and the frequency of operation.

19.Which mode of radiation occurs in an helical antenna due to smaller dimensions of helix as compared to a wavelength?
a.Normal
b.Axial
c.Both a and b
d.None of the above

20.By how many times is an input impedance of a folded dipole at resonance greater than that of an isolated dipole with same length as one of its sides?
a.2
b.3
c.4
d.6

21.How do the elements of an active region behave?
a.Inductive
b.Capacitive
c.Resistive
d.None of the above

22.In an electrically large loop, an overall length of the loop is equal to ______
a.λ/2
b.λ
c.λ/10
d.λ/50

23.What is /are the advantages of using ferrite loops?
A. Increase in Magnetic field intensity
C. Decrease in Magnetic field intensity
a.A & B
b.C & D
c.A & D
d.B & C

24. In an electrically large loop, an overall length of the loop is equal to ______
a. λ/2
b. λ
c. λ/10
d. λ/50

25. What is /are the advantages of using ferrite loops?
A. Increase in Magnetic field intensity
C. Decrease in Magnetic field intensity
a. A & B
b. C & D
c. A & D
d. B & C

26. What would happen if the rms value of induced emf in loop acquires an angle θ = 90°?
a. Wave is incident in direction of plane of the loop with induced maximum voltage
b. Wave is incident normal to plane of the loop with no induced voltage
c. Wave is incident in opposite direction of plane of the loop with minimum voltage
d. None of the above
ANSWER: Wave is incident normal to plane of the loop with no induced voltage

27. What is the far-field position of an electric short dipole?
a. Along x-axis
b. Along y-axis
c. Along z-axis
d. Along xy plane

28. If the radius of loop is λ/ 20 in a free space medium,what will be the radiation resistance of 8-turn small circular loop?
a. 0.7883 Ω
b. 50.45 Ω
c. 123.17 Ω
d. 190.01 Ω

29. For receiving a particular frequency signal, which tuning component must be used by the loop to form a resonant circuit for tuning to that frequency?
a. Capacitor
b. Inductor
c. Resistor
d. Gyrator

30. According to the directivity of a small loop, which value of ‘θ’ contributes to achieve the maximum value of radiation intensity (Umax)?
a. 0°
b. 90°
c. 180°
d. 270°

a. Poor
b. Good
c. Better
d. Excellent

32. On which factor/s do/does the radiation field of a small loop depend?
a. Shape
b. Area
c. Both a and b
d. None of the above

33. In an electrically small loops, the overall length of the loop is ______ one-tenth of a wavelength.
a. Less than
b. Equal to
c. Greater than
d. None of the above

#### Module 3

1. Which of the following is false regarding Antenna array?
a) Directivity increases
b) Directivity decreases
c) Beam width decreases
d) Gain increases
Explanation: A single antenna provides low gain and less directivity. To increase the directivity antenna arrays are used. With the antenna arrays, directivity and gain increases and beam width decreases.

2. Electrical size of antenna is increased by which of the following?
a) Antenna Array
b) Decreasing the coverage area
c) Increasing the coverage area
d) Using a single antenna
Explanation: To increase the directivity antenna arrays are used. With the antenna arrays, directivity and gain increases and beam width decreases. The electrical size of the antenna is increased by placing an array antenna together to achieve high directivity.

3. For long distance communication, which of the property is mainly necessary for the antenna?
a) High directivity
b) Low directivity
c) Low gain
Explanation: Long distance communication requires antenna with high directivity. To increase the directivity antenna arrays are used. With the antenna arrays, directivity and gain increases and beam width decreases.

4. Which of the following is false about the single antenna for long distance communication?
a) Enlarging may create side lobes
b) No side lobes
c) High directivity is required
d) High Gain is required
Explanation: High directive antennas are required for the long distance communications. The array of antennas is used to increase the directivity. The directivity can be increased by increasing the dimensions of antenna but it creates side lobes.

5. The electrical size of antenna is increased by antenna array to avoid size lobes compared to single antenna.
a) True
b) False
Explanation: Increasing the dimensions of antennas may lead to the appearance of the side lobes. So by placing a group of antennas together the electrical size of antenna can be increased. With the antenna arrays, directivity and gain increases and beam width decreases.

6. A uniform linear array contains _____________
a) N elements placed at equidistance and fed currents of equal magnitude and progressive phase shift
b) N elements at non-equidistance and fed currents of equal magnitude and progressive phase shift
c) N elements at equidistance and fed currents of unequal magnitude and progressive phase shift
d) N elements at equidistance and fed currents of unequal magnitude and equal phase shift
Explanation: An array is said to be linear if N elements are spaced equally long the line and is a uniform array if the current is fed with equal magnitude to all elements and progressive phase shift along the line. High directivity can be obtained by antenna array.

7. Total resultant field obtained by the antenna array is given by which of following?
a) Vector superposition of individual field from the element
b) Maximum field from individual sources in the array
c) Minimum field from individual sources in the array
d) Field from the individual source
Explanation: The total resultant field is obtained by adding all the fields obtained by the individual sources in the array. An Array containing N elements has the resultant field equal to the vector superposition of individual field from the elements.

8. If the progressive shift in antenna array is equal to zero then it is called _________
b) End-fire
c) Yagi-uda
d) Fishbone antenna
Explanation: The total phase difference of the fields is given by Ѱ=kdcosθ+β
Here β is the progressive phase shift
⇨ β=0, array is a uniform broadside array
⇨ β=180, array is a uniform end-fire array
Yagi-uda antenna, fishbone antenna are end-fire antenna array.

9. What is the progressive phase shift of the end-fire array?
a) 0
b) 90
c) 180
d) 60
Explanation: The progressive phase shift of the end-fire array is 180°. It is a linear array whose direction of radiation is along the axis of the array. For a broadside array it is 0°.

10. Which of the following statement about antenna array is false?
a) Field pattern is the product of individual elements in array
b) Field pattern is the sum of individual elements in array
c) Resultant field is the vector superposition of the fields from individual elements in array
d) High directivity can be achieved for long distance communications
Explanation: The total resultant field is obtained by adding all the fields obtained by the individual sources in the array. Radiation pattern is obtained by multiplying the individual pattern of the element. Field pattern is the product of individual elements in array. Antenna arrays are used to get high directivity with less side lobes.

11. The directivity of Yagi-Uda antenna is increased by adding ______
a) reflectors
b) driven element
c) directors
d) boom
Explanation: Addition of directors leads to focus the beam in the forward direction. So, directors will increase the gain of antenna. Folded dipole acts like a feed or driven element. Reflectors will increase the directivity of antenna by reflecting all energy towards radiation direction of antenna. Boom is a center rod on which elements are mounted.

12. Directors are used to increase ______ of the Yagi-Uda antenna.
a) Directivity
b) Gain
c) Back lobe
d) Reflection away from the radiation
Explanation: Reflectors will increase the directivity of antenna by reflecting all energy towards radiation direction of antenna. Addition of directors leads to focus the beam in the forward direction. So, directors will increase the gain of antenna.

13. What is the radiation pattern of a Yagi-Uda antenna?
b) End-fire
c) Collinear
Explanation: Radiation pattern of a Yagi-Uda antenna is end-fire. It has its main beam parallel to the axis of antenna (boom). The addition of directors will increase the gain of antenna while reflectors will increase the directivity of antenna.

14. A narrow beam-width is obtained through a large number of directors.
a) True
b) False
Explanation: Large number of directors increases the direction of radiation towards the desired direction and a narrow beam-width is obtained. It also helps in increasing the directivity of antenna.

15. The dipole to which the power is applied directly from the feeder in the Yagi-Uda antenna is called as _____
a) Director
b) Reflector
c) Driven element
d) Boom
Explanation: The dipole to which the power is applied directly from the feeder in the Yagi-Uda antenna is called driven element. Directors add the field of the driven element and will excite the next parasitic element. Reflectors will increase the directivity of antenna.

16. Folded dipole is used than a single dipole in Yagi-Uda to obtain wider frequency range.
a) True
b) False
Explanation: Folded dipole produces flatter impedance v/s frequency compared to single dipole. So, folded dipole is used in Yagi-Uda to obtain wider frequency range.

17. In which of the following bands Yagi-Uda antenna operates?
a) HF-UFH
b) VLF-MF
c) LF-HF
d) UHF-EHF
Explanation: Yagi-Uda antenna operates mostly in the HF to UFH band frequency. IT ranges from 3MHz to 3GHz.
VLF-MF: 3 kHz to 3MHz
LF-HF: 30 kHz to 30MHz
UHF –EHF: 300MHz to 300GHz.

18. A Yagi-Uda antenna is ____
a) Only a super directive antenna
b) Only a super gain antenna
c) Both super directive and super gain
d) Neither super directive nor super gain
Explanation: A Yagi-Uda antenna provides high directivity by increasing reflectors and gain due to the directors. Directors will increase the forward gain of the antenna. So it is both super directive and super gain antenna.

19. In order to convert the bidirectional dipole to unidirectional system, we use _______
a) Active element
b) Driven element
c) Parasitic element
d) Isolator
Explanation: We use reflectors and directors which are passive elements also known as the parasitic elements to increase the directivity and gain if the antenna.

20. Which of the following will add the field of the driven element and will excite the next parasitic element to increase the gain of the antenna?
a) Director
b) Reflector
c) Active element
d) Boom
Explanation: Directors add the field of the driven element and will excite the next parasitic element. Directors will increase the gain of the antenna in the forward direction. Reflectors will add fields of the driven element in the direction from reflector to driven element.

21. Which of the following is a narrow band antenna?
a) Rhombic antenna
b) Yagi-Uda antenna
c) Log periodic antenna
d) Horn antenna
Explanation: Yagi-Uda antenna is a narrow band antenna. Rhombic, Log periodic and horn are wide band antennas. More number of channels is used in the Log periodic antenna compared to the Yagi-Uda in TV reception.

22. Log periodic antenna uses which range of frequencies?
a) VHF and UHF
b) VHF and SHF
c) MF and VHF
d) HF and VHF
Explanation: Log periodic antenna uses around 30MHz to 3GHz frequency range.
MF – Medium Frequency – 300-3000 KHz
HF – High Frequency – 3-30 MHz
VHF – Very high frequency – 30-300 MHz
UHF – Ultra high frequency – 300MHz to 3GHz
So it uses VHF and UHF.

23. Log periodic antenna is frequency dependent.
a) True
b) False
Explanation: Log periodic antenna is frequency independent. The geometrical structure of the antenna changes according to the wavelength. It is also called as Frequency Independent antenna. Its electrical performance is dependent on logarithmic of frequency only.

24. Which of the following antenna is known as Frequency Independent antenna?
a) LPDA
b) Dipole antenna
c) Rhombic antenna
d) Yagi-Uda antenna
Explanation: LPDA means Log periodic Dipole Array antenna. It’s all characteristics such as impedance, radiation pattern are frequency independent. So it is also called as Frequency independent antenna.

25. What is the approximate gain of LPDA for best performance?
a) 1 dB to 5 dB
b) 4 dB to 18 dB
c) 8 dB to 20 dB
d) 7 dB to 12 dB
Explanation: For best performance of the LPDA antenna, the gain lies between 7 to 12dB. It is a broadband antenna. LPDA is a wideband antenna and provides gain and directivity combined over a wide band of frequencies.

26. In order to get more number of channels in TV reception, we prefer Yagi-Uda than LPDA.
a) True
b) False
Explanation: LPDA is a broadband antenna while Yagi-Uda is a narrow band antenna. To increase the more number of channels for TV reception we prefer LPDA. It is also used for long distance communication.

27. Which of the following statements is false?
a) Log periodic antenna is a broadband antenna
b) The active region doesn’t change with the change in frequency in Log Periodic antenna
c) The geometry structure of the dipole changes proportional to the wavelength in LPDA
d) Impedance is function of logarithmic of frequency
Explanation: In Log period antenna, the active region changes with the change in frequency. There are three regions of operation in the LPDA.Impedance is function of logarithmic of frequency in LP so it is called log periodic antenna.

28. The geometrical design of the Log periodic depends on _____
a) Scaling factor
b) Gain
c) Impedance
d) Stability
Explanation: Scaling factor is the ratio of the lengths and spacing’s of the dipoles. It is also called as periodicity factor. If rn denotes the length of the nth dipole then the scaling factor is given by
Scaling factor = rnrn+1

29. The length of the director compared to the driven element is ______
a) Greater
b) Smaller
c) Independent to each other
d) Depends on the type of driven element
Explanation: The length of the director is less than the driven element. It is shorter than half wavelength of the dipole. Director is used to increase the gain of antenna.

30. The length of the reflector compared to the driven element is ______
a) Greater
b) Smaller
c) Independent to each other
d) Depends on the type of driven element
Explanation: Reflector is used to reflect all the energy towards the radiation direction. It increases the front to back lobe ratio. So always the reflector length is greater than the driven element length.

31. The distance between directors of Yagi-Uda antenna is ____
a) 0.2λ
b) 0.49λ
c) 0.52λ
d) 0.62λ
Explanation: The distance between directors of Yagi-Uda antenna is 0.2λ. The directors will increase the gain.

32. For a feeder length of 0.5λ, which among the following would be the reflector length?
a) 0.525λ
b) 0.425λ
c) 0.23λ
d) 0.35λ
Explanation: The reflector length is approximately 5% greater than the driven element length.
So, l = 0.525λ is correct as it is the only option which is greater than 0.5λ.

33. If the input impedance of a half wave dipole Yagi-Uda is 73Ω, then input impedance of a half wave folded dipole as driven element is ____
a) 73Ω
b) 146Ω
c) 36.5Ω
d) 292Ω
Explanation: Half wave folded dipole impedance is 4 times the half wave dipole.
⇨ Z = 4 × 73 = 292Ω.

34. What is the reflector length (in feet) for a three element Yagi-Uda array, operating at a frequency 500MHz?
a) 2
b) 0.2
c) 1
d) 0.1
Explanation: For a 3 element Yagi-Uda array,
Reflector length (feet) = 500/f (MHz) = 500/500 = 1 feet

35. What is the driven length (in feet) for a three element Yagi-Uda array, operating at a frequency 500MHz?
a) 0.95
b) 0.2
c) 1
d) 2
Explanation: For a 3 element Yagi-Uda array,
Driven element length (feet) = 475/f (MHz) = 475/500 = 0.95 feet.

36. What is the Director length (in feet) for a three element Yagi-Uda array, operating at a frequency 500MHz?
a) 0.91
b) 1
c) 2
d) 0.5
Explanation: For a 3 element Yagi-Uda array,
Director element length (feet) = 455/f (MHz) = 455/500 = 0.91 feet.

37. For a feeder length of 0.5λ, which among the following would be the director length?
a) 0.525λ
b) 0.455λ
c) 0.493λ
d) 0.55λ
Explanation: The director length is approximately 5% less than the driven element length.
⇨ 0.5-(0.5(5/100)) = 0.475
So, l = 0.455λ is correct as it is the only option which is less than 0.475λ.

#### Module 4

1. Which of the following type does horn antenna belongs?
a) Wire Antenna
b) Array Antenna
c) Aperture Antenna
d) Lens Antenna
Explanation: Horn antenna belongs to Aperture antenna. Flaring done is done at the aperture of the rectangular waveguide gives different types of horn antenna. Dipole belongs to Wire antenna. Yagi-Uda is an array antenna. Convex-plane is example for lens antenna.

2. Which of the following antenna is mainly used for broadband signals?
a) Marconi antenna
b) Horn antenna
c) Wire antenna
d) Yagi-Uda antenna
Explanation: Horn antenna is used for broadband signals due to its flared nature. It is used to properly match the waveguide to a large radiating aperture by shaping transition gradually. It is used in 300MHz to 30GHz frequency range.

3. In which of the following bands the horn antenna operates?
a) HF and VHF
b) UHF and LF
c) UHF and SHF
d) LF and VHF
Explanation: Horn antenna is used in the frequency range 300MHz to 30GHZ. So, it is used in UHF and SHF frequency bands.
HF- VHF: 3MHz to 300MHz
LF-UHF: 30kHz to 3GHz
LF-VHF: 30kHz to 300MHz

4. In a horn antenna, with increase in aperture, the directivity is ____ and diffraction is ______
a) increased, decreased
b) decreased, increased
c) increased, increased
d) decreased, decreased
Explanation: Horn antenna is designed to improve the directivity and reduce the diffractions. It is used to properly match the waveguide to a large radiating aperture by shaping transition gradually. So, reflections are also decreased.

5. In Horn antennas impedance matching is provided by _______
a) flaring
b) increasing Power
c) decreasing axial length
d) Balun
Explanation: In horn antennas, we use Flaring technique for impedance matching. The sides of the waveguide are flared to match the impedance and improve the radiation efficiency.

6. Principle used in Horn antenna is Huygens principle.
a) True
b) False
Explanation: Horn antenna uses Huygens principle where aperture field is considered as a second source which gives rise to far field. It states that each point on a primary wave front can be considered to be a new source of a secondary spherical wave and that a secondary wave front can be constructed as the envelop of these secondary spherical waves.

7. Which of the following doesn’t apt for flaring?
a) Improve Gain
b) Impedance matching
c) Decreases side lobes
d) Improve Standing waves
Explanation: Flaring is done to provide the impedance matching. So, the reflections are minimized so there will be no standing waves. Side lobes will be reduced so the forward gain is also improved.

8. The radiation pattern of H-plane Sectoral horn is narrower than the E-plane Sectoral horn.
a) True
b) False
Explanation: The radiation pattern of H-plane Sectoral horn is narrower than the E-plane Sectoral horn. It is because of the dimension of the horn antenna in that direction.

9. The small the flare angle, ___ is the directivity and ____ is the beam width.
a) high, low
b) low, high
c) low, low
d) high, high
Explanation: The smaller flare angle means the beam is narrower. The Beamwidth and directivity are inversely proportional to each other. If beamwidth increases then directivity will decrease. So, for a small fare angle, the directivity is more and beamwidth is less.

10. For a horn antenna, in which flaring is done only in one direction is ________
a) Conical antenna
b) Sectoral antenna
c) Pyramidal horn antenna
d) Exponential horn antenna
Explanation: In Sectoral horn antenna, flaring is done only in one direction. Depending on the flaring direction with respect to field propagation, it is divided into E-plane or H-plane horn antenna. Conical horn flared cross section is in shape of a cone.Pyramidal horn flared cross section is in shape of a four-sided pyramid. In exponential horn, the separation of sides increases as a function of length.

11. If flaring is done in the boarder direction of the rectangular waveguide then it is called ______
a) E-plane horn
b) H-plane horn
c) Conical horn
d) Pyramidal horn
Explanation: If the flaring is done in the electric field that means in the boarder direction of the rectangular waveguide, then it is called E-plane horn antenna.

12. If flaring is done in the magnetic field direction of the rectangular waveguide then it is called ______
a) E-plane horn
b) H-plane horn
c) Conical horn
d) Pyramidal horn
Explanation: In Sectorial horn antenna, flaring is done only in one direction.If the flaring is done in the magnetic field direction, then it is called H-plane horn antenna.

13. Which of the following antenna has the parallel slots along the inside surface of the horn?
a) E-plane horn
b) Pyramidal horn
c) Exponential horn
d) Corrugated horn
Explanation: A Corrugated horn has parallel slots or grooves which are small in size compared to the wavelength. These are present along the inside surface of the horn and are transverse to the axis.These corrugated antennas have wider bandwidths and minimizes the side lobes.

14. In which of the following antennas the separation of sides increases as a function of length?
a) Conical horn
b) Exponential tapered pyramidal horn
c) Pyramidal horn
d) Sectoral horn
Explanation: In exponentially tapered pyramidal horn, the transition region is gradually tapered exponentially to minimize the reflections. These are mainly used when reflections in the waveguide are critical.

15. If the walls of the circular waveguide are flared out, then it is called _____
a) Pyramidal horn
b) E-plane horn
c) H-plane horn
d) Conical horn
Explanation: In conical horn, the walls of the circular waveguide are flared out. For pyramidal horn, the walls of the rectangular waveguide are flared out in both directions.

16. If the all the walls of rectangular waveguide are flared out, then it is called ______
a) Pyramidal horn
b) Conical horn
c) E-plane horn
d) H-plane horn
Explanation: For pyramidal horn, all the walls of the rectangular waveguide are flared out. E-plane and H-plane are Sectoral horn antennas which are flared in only one direction.

17. Which of the following refers to the pattern of reflector in the reflector antenna?
a) Primary pattern
b) Secondary pattern
c) Reflector pattern
d) Feed pattern
Explanation: In a reflector antenna, primary pattern is the feed pattern and secondary pattern is the pattern of reflector. Reflector antennas are high gain antenna and are used in RADARs and for some communication purpose.

18. Reflector antenna operates on the Geometric optics principle?
a) True
b) False
Explanation: Reflector antenna is high gain antenna and works on the principle of the Geometric optics. Geometrical optics shows that if a beam of parallel rays is incident on a reflector antenna whose geometrical shape is a parabola, then the array beams will converge at the focal point.

19. Which of the following is a dual reflector antenna?
a) Cassegrain antenna
b) Parabolic antenna
c) Offset reflector antenna
d) Wire antenna
Explanation: A dual reflector antenna consists of two reflectors and one feed antenna. Cassegrain antenna is the best example of dual reflector antenna since it contains main reflector as parabolic and sub-reflector as hyperbola.

20. Which of the following combination forms a Cassegrain antenna?
a) The main reflector is parabolic and sub-reflector is hyperbolic
b) The main reflector is parabolic and sub-reflector is concave
c) The main reflector is hyperbolic and sub-reflector is parabolic
d) The main reflector is hyperbolic and sub-reflector is convex
Explanation: A Cassegrain antenna is a dual reflector antenna and is axis symmetry. It consists of two reflectors and one primary feed. The main reflector is parabolic and sub-reflector is hyperbolic (convex).

21. Which of the following efficiency is used to measure the power-loss at the feed pattern which is intercepted by reflector?
a) Spillover
b) Illumination
c) Taper
d) Aperture
Explanation: When the feed pattern exceeds beyond reflectors rim, not all the energy is redirected by the reflector. This power loss is measure results in spillover efficiency. Illumination efficiency is the combination of both taper and spillover efficiency. Aperture efficiency is the ratio of effective aperture to physical aperture. Taper efficiency gives the directivity measure of the antenna.

22. What is the value of magnification of the Cassegrain antenna if its sub-reflector eccentricity is 2?
a) 3
b) 2
c) 1/3
d) 1/2
Explanation: Given eccentricity e=2
Magnification M=e+1e−1=3

23. Which of the following is false regarding a reflector antenna?
a) Reflector antennas are high gain antennas with two antennas
b) Both the primary and secondary antennas are excited
c) The pattern of the reflector in the reflector antenna is the Secondary pattern
d) A dual reflector contains two reflectors and one primary feed
Explanation: In a reflector antenna the horn or a dipole acts as a feed and the antenna which is excited is the primary antenna. Reflector is the secondary antenna. Reflector antenna is a high gain antenna consisting of primary and secondary antennas.

24. Which of the following is not a reflector antenna?
a) Convex-convex
b) Corner
c) Gregorian
d) Cassegrain
Explanation: Corner, Cassegrain and Gregorian belong to reflector antenna. Convex-convex is a type of lens antenna. Gregorian is a dual reflector antenna with a concave sub-reflector.

25. When a reflector is placed at the foci along the feed it is called ____ antenna
a) Dual reflector antenna
b) Plane antenna
c) Wire antenna
d) Convex-Convex
Explanation: Usually a feed forward is used in reflector antenna and feed antenna is placed at focus of the reflector. When a sub-reflector is placed at the focus along with the feed antenna it is called dual reflector antenna. Example of dual reflector antenna: Cassegrain antenna.
Convex-Convex is a lens antenna.

26. Which of the following is used as a secondary antenna in the reflector antenna?
a) Horn
b) Feed antenna
c) Parabolic
d) Dipole
Explanation: A parabolic reflector is used as a secondary antenna. Horn and dipole are used for feed antenna. Feed antenna of the reflector antenna is called Primary antenna.

27. Corner reflector is designed for radiation in forward direction unlike in plane reflector.
a) True
b) False
Explanation: The plane reflector allows back and side radiation. In order to avoid this it is modifies to a corner reflector which consists of two plane reflectors joined at a corner to allow radiation in forward direction only.

28. In a corner reflector, included angle α refers to _______
a) angle at which two plane reflectors are joined
b) angle between vertex and the feed radiator
c) angle between major axis to the main beam
d) angle between vertex and the main beam axis
Explanation: A corner reflector consists of two plane reflectors joined at a corner to allow radiation in forward direction only. Included angle is the angle at which two reflectors are joined, measured at the corner.

29. In order to achieve good system efficiency in a corner reflector, the spacing between the vertex and the feed must be ______ as included angle decreases.
a) Increased
b) Decreased
c) Constant
d) Either increases or decreases
Explanation: The system efficiency in a corner reflector depends on the spacing between vertex of the corner and the feed. It is adjusted depending on the included angle. As the included decreases, spacing must be increased.

30. In a corner reflector antenna, if the spacing between vertex of reflector and feed is 2m then side length of reflector sheet is _____cm.
a) 4
b) 2
c) 400
d) 200
Explanation: In a corner reflector antenna, side length of reflector sheet and l=2d
Where, d is distance between feed and vertex of the reflector.
Given d=2m so l=2*2=4m=400cm.

31. Which of the following statements is false for a corner reflector antenna?
a) Increases directivity in the forward direction
b) Back radiation is not reduced compare to the plane reflector
c) System efficiency depends on spacing between reflector vertex and the feed
d) Angle between the reflecting plates is called included angle
Explanation: Compared to the plane reflector antenna, back and side radiations are reduced in the corner reflector. A corner reflector consists of two plane reflectors joined at a corner to allow radiation in forward direction only. As the included angle decreases, spacing will increases.

32. The number of images, polarity and position in the analysis of the radiation field of corner reflector depends on what?
a) Only included angle
b) Polarization of feed element
c) Both included angle & Polarization of feed element
d) Neither included angle nor Polarization of feed element
Explanation: The number of images, polarity and position in the analysis of the radiation field of corner reflector depends on both included angle & Polarization of feed element with perpendicular polarization. Angle between the reflecting plates is called included angle.

33. What is the ratio of focal length to diameter for practical applications in a parabolic reflector?
a) 0.25 to 0.5
b) < 0.25
c) 0.125 to 0.3
d) 0.5 to 1
Explanation: The ratio of focal length (f) to diameter (d) f/d < 14 indicates radiation away from the parabolic surface of the reflector. So for practical applications it lies between 0.125 and 0.5.

34. Which of the following is false regarding a paraboloid antenna?
a) Spill over decreases due to back lobe of primary radiator
b) Feed placed at the focus is used to improve the beam pattern
c) Pill box provides wide beam in one plane and narrow beam in other plane
d) At lower frequencies parabolic antennas are not used frequently
Explanation: Spill over occurs due to the non-captured radiation by the reflector. From the primary radiators also some of forward radiation gets added up with the desired parallel beams. This is called back lobe radiation. It increases due to the back lobe of the primary radiator.

35. Which of the following paraboloid reflector is formed by cutting some part of paraboloid to meet requirements?
a) Truncated paraboloid
b) Cassegrain
c) Corner
d) Pill box
Explanation: When a portion of the paraboloid reflector is cut off or truncated it is called as truncated paraboloid. Pill box provides wide beam in one plane and narrow beam in other plane. Cassegrain is a dual reflector antenna and Corner reflector is also a type of reflector antenna.

36. Which of the following is used to produce wide beam in one plane and narrow beam in other plane?
a) Pill box
b) Truncated paraboloid
c) Cassegrain
d) Paraboloid with rectangular aperture
Explanation: Pill box is short parabolic right cylinder enclosed by parallel plates. It produces a wide beam in one plane and narrow beam in other plane. Cassegrain is a dual reflector. Truncated is a type of paraboloid.

37. In a paraboloid antenna, all rays leaving the focal point are collimated along the reflector’s axis after reflection.
a) True
b) False
Explanation: According to the geometry of the paraboloid reflector,
⇨ All rays leaving the focal point are collimated along the reflector’s axis after reflection.
⇨ All overall ray path lengths (from the focal point to the reflector and on to the aperture plane) are the same and equal to 2F.

38. Which of the following wave conversion mechanism is performed in a parabolic reflector antenna?
a) Plane to spherical
b) Spherical to plane
c) Performs both plane to spherical and spherical to plane
d) Elliptic polarization
Explanation: In a parabolic reflector antenna, the wave conversion mechanism used is spherical to plane. It works on the principle of geometric optics. The reflected plane waves travel parallel o the major axis of the reflector.

#### Module 5

1. Microstrip can be fabricated using:
a) Photolithographic process
b) Electrochemical process
c) Mechanical methods
d) None of the mentioned
Explanation: Microstrip lines are planar transmission lines primarily because it can be fabricated by photolithographic processes and is easily miniaturized and integrated with both passive and active microwave devices.

2. The mode of propagation in a microstrip line is:
a) Quasi TEM mode
b) TEM mode
c) TM mode
d) TE mode
Explanation: The exact fields of a microstrip line constitute a hybrid TM-TE wave. In most practical applications, the dielectric substrate is very thin and so the fields are generally quasi-TEM in nature.

3. Microstrip line can support a pure TEM wave.
a) True
b) False
c) Microstrip supports only TM mode
d) Microstrip supports only TE mode
Explanation: The modeling of electric and magnetic fields of a microstrip line constitute a hybrid TM-TE model. Because of the presence of the very thin dielectric substrate, fields are quasi-TEM in nature. They do not support a pure TEM wave.

4. The effective di electric constant of a microstrip line is:
a) Equal to one
b) Equal to the permittivity of the material
c) Cannot be predicted
d) Lies between 1 and the relative permittivity of the micro strip line
Explanation: The effective dielectric constant of a microstrip line is given by (∈r + 1)/2 + (∈r-1)/2 * 1/ (√1+12d/w). Along with the relative permittivity, the effective permittivity also depends on the effective width and thickness of the microstrip line.

5. Effective dielectric constant of a microstrip is given by:
a) (∈r + 1)/2 + (∈r-1)/2 * 1/ (√1+12d/w)
b) (∈r+1)/2 + (∈r-1)/2
c) (∈r+1)/2 (1/√1+12d/w)
d) (∈r + 1)/2-(∈r-1)/2
Explanation: The effective dielectric constant of a microstrip line is (∈r + 1)/2 + (∈r-1)/2 * 1/ (√1+12d/w). This relation clearly shows that the effective permittivity is a function of various parameters of a microstrip line, the relative permittivity, effective width and the thickness of the substrate.

6. The effective dielectric constant of a micro strip line is 2.4, then the phase velocity in the micro strip line is given by:
a) 1.5*108 m/s
b) 1.936*108 m/s
c) 3*108 m/s
d) None of the mentioned
Explanation: The phase velocity in a microstrip line is given by C/√∈r. substituting the value of relative permittivity and the speed of light in vacuum, the phase velocity is 1.936*108 m/s.

7. The effective di electric constant of a micro strip line with relative permittivity being equal to 2.6, with a width of 5mm and thickness equal to 8mm is given by:
a) 2.6
b) 1.97
c) 1
d) 2.43
Explanation: The effective dielectric constant of a microstrip line is given by (∈r + 1)/2 + (∈r-1)/2 * 1/ (√1+12d/w). Substituting the given values of relative permittivity, effective width, and thickness, the effective dielectric constant is 1.97.

8. If the wave number of an EM wave is 301/m in air , then the propagation constant β on a micro strip line with effective di electric constant 2.8 is:
a) 602
b) 503.669
c) 150
d) 200
Explanation: The propagation constant β of a microstrip line is given by k0√∈e. ∈e is the effective dielectric constant. Substituting the relevant values, the effective dielectric constant is 503.669.

9. For most of the micro strip substrates:
a) Conductor loss is more significant than di electric loss
b) Di electric loss is more significant than conductor loss
c) Conductor loss is not significant
d) Di-electric loss is less significant
Explanation: Surface resistivity of the conductor (microstrip line) contributes to the conductor loss of a microstrip line. Hence, conductor loss is more significant in a microstrip line than dielectric loss.

10. The wave number in air for EM wave propagating on a micro strip line operating at 10GHz is given by:
a) 200
b) 211
c) 312
d) 209
Explanation: The wave number in air is given by the relation 2πf/C. Substituting the given value of frequency and ‘C’, the wave number obtained is 209.

11. The effective dielectric constant ∈r for a microstrip line:
a) Varies with frequency
b) Independent of frequency
c) It is a constant for a certain material
d) Depends on the material used to make microstrip
Explanation: The effective dielectric constant of a microstrip line is given by (∈r + 1)/2 + (∈r-1)/2 * 1/ (√1+12d/w). The equation clearly indicates that the effective dielectric constant is independent of the frequency of operation, but depends only on the design parameters of a microstrip line.

12. With an increase in the operating frequency of a micro strip line, the effective di electric constant of a micro strip line:
a) Increases
b) Decreases
c) Independent of frequency
d) Depends on the material of the substrate used as the microstrip line
Explanation: As the relation between effective permittivity and the other parameters of a microstrip line indicate, effective dielectric constant is not a frequency dependent parameter and hence remains constant irrespective of the operation of frequency.

13. Which of the following is the most common version of the printed antenna?
a) Horn antenna
b) Microstrip antenna
c) Wire antenna
d) Lens antenna
Explanation: Microstrip antenna is a printed antenna. It is fabricated using photolithography technique. It consists of a radiation patch on one side of dielectric and a ground plane on other side. The patch can be of any shape like circular or rectangular.

14. In which of the following type of antenna a patch is created during fabrication?
a) Microstrip antenna
b) Horn antenna
c) Wire antenna
d) Lens antenna
Explanation: In Microstrip antenna patch is created on the dielectric substrate using photo-etching. The shape and size of patch may vary the return loss. Horn, Wire and Lens doesn’t have any patch. Horn is a waveguide antenna and a wire antenna is made of dipoles.

15. In Microstrip antenna, the patch and feed line is photo etched on dielectric substrate
a) True
b) False
Explanation: Microstrip antenna is a printed antenna which is fabricated using photolithography technique. Its design process consists of a ground plane and a dielectric substrate in which patch is created. The source is connected to it through a feed line by photo etching process.

16. The shape of the patch in rectangular Microstrip antenna is ____
a) Rectangular
b) Circular
c) Cylindrical
d) Elliptical
Explanation: The antenna is named under the shape of the patch. For a rectangular Microstrip antenna, the patch shape is rectangle. For a general Microstrip antenna patch can be any shape like rectangle, circular, elliptic, triangle.

17.Which antennas are renowned as patch antennas especially adopted for space craft applications?
a. Aperture
b. Microstrip
c. Array
d. Lens

#### Module 6

1. Which of the following antenna range is used for small antennas?
a) Indoor ranges
b) Outdoor ranges
c) Reflection range
d) Slant range
Explanation: Indoor ranges are used for the small antenna as the far field region criteria is achieved in limited space. Space restriction is found in indoor range measurement. Outdoor range is used for larger antenna and in open environment. Reflection range, Slant range and elevation range comes under outdoor ranges.

2. Which of the following doesn’t come under indoor ranges?
a) Slant range
b) Anechoic chamber
c) Tampered chamber
d) Compact ranges
Explanation: For small antennas whose far filed criterion is obtained within in a limited range, indoor ranges are applicable. Reflection range, Slant range and elevation range belongs to outdoor ranges which is applicable for the larger antennas in open environment. Anechoic, tampered chambers and compact ranges come under indoor ranges.

3. What is the frequency of antennas used for Reflection range?
a) 300MHz to 16GHz
b) 3 MHz to 16MHz
c) 16MHz to 300MHz
d) 3GHz to 30GHz
Explanation: Reflection range, Elevation range and Slant range comes under outdoor ranges. The reflection range is an outdoor antenna range test where the antennas are operated at UHF and 16GHz. Ground acts as a reflector.

4. Which of the following doesn’t come under outdoor ranges?
a) Reflection range
b) Anechoic chamber
c) Slant range
d) Elevation range
Explanation: Reflection range, Slant range and elevation range belongs to outdoor ranges. Anechoic, tampered chambers and compact ranges are part of indoor ranges. Indoor ranges are used for the small antenna as the far field region criteria is achieved in limited space and outdoor ranges for larger antennas.

5. Height criteria required for mounting AUT under elevated range test is ______
a) hr ≤ 4D
b) hr ≥ 4D
c) hr ≥ 2D
d) hr ≤ 2D
Explanation: Elevated range test is one of the outdoor ranges. The height required to mount the AUT for the elevation range test is given by hr ≥ 4D, where D is the dimension of AUT.

6. If the dimension of antenna under test (AUT) is 2m the minimum height required to mount it for elevation range is _______
a) 8m
b) 8cm
c) 4m
d) 2m
Explanation: The minimum height required to mount antenna under test for the elevation range is given by a relation hr ≥ 4D, where D is the dimension of AUT.
Minimum height required hr=4D=4*2=8m

7. For AUT to encounter uniform illumination which of the following is true?
a) Height of AUT should be equal to or more than four times the dimension of antenna
b) Height of AUT should be less than four times the dimension of antenna
c) Height of AUT should be equal to or more than two times the dimension of antenna
d) Height of AUT should be less than two times the dimension of antenna
Explanation: The amplitude variation over AUT should be more than 0.2dB to get AUT encounter uniform illumination. To satisfy that the height criteria of AUT should be equal to or more than four times the dimension of antenna.

8. Which of the following antenna ranges are used to avoid limitations due to electromagnetic interference?
a) Anechoic Chambers
b) Slant height
c) Outdoor ranges
d) Reflection range
Explanation: Indoor ranges are used to avoid limitations due to electromagnetic interference and also ignore the environmental changes in surroundings. Indoor ranges have space restrictions unlike outdoor ranges. Anechoic, tampered chambers and compact ranges come under indoor ranges. Reflection range, Slant range and elevation range comes under outdoor ranges.

9. Antenna range refers to the measurement of antenna parameters.
a) True
b) False
Explanation: The volume, in which the antenna parameters are measured, is called the antenna range. They are of two types. Indoor ranges are used to avoid limitations due to electromagnetic interference. Outdoor ranges are used for larger antenna in environmental surroundings.

10. Which of the following is false regarding elevated range test?
a) To get AUT encounter uniform illumination, the amplitude variation should be less than 0.2dB
b) The height criteria of AUT should be equal to or more than four times the dimension of antenna
c) Range diffraction fences are used to reduce the antenna reflections.
d) To get AUT encounter uniform illumination, the amplitude variation should be more than 0.2dB
Explanation: To get AUT encounter uniform illumination, the amplitude variation should not be more than 0.2dB. The height required to mount the AUT for the elevation range test is given by hr ≥ 4D, where D is the dimension of AUT. Range diffraction fences are used to reduce the antenna reflections.

11. Which of the following is used mostly for the calibration of standard gain of antenna?
a) Absolute gain
b) Gain transfer method
c) Gain compromise method
d) Both gain transfer and absolute gain method
Explanation: In absolute gain method, the prior knowledge of gain of antennas used in the measurements is not necessary and it is used for standard gain calibration. Gain transfer or Gain compromise method requires the standard gains of the antennas used for measurements to compare the AUT.

12. In which of the following method does not require standard gain of antennas for gain measurements to compare AUT?
a) Absolute gain
b) Gain transfer method
c) Gain compromise method
d) Both gain transfer and absolute gain method
Explanation: Gain transfer and gain compromise methods require the standard gain calibration of antennas for gain measurements to compare the antennas under test. In Absolute gain method, gain of the antennas which are to be compared are known priory and this is used for the standard gain calibration

13. Antenna efficiency of a lossless isotropic antenna is dB is ____
a) 0
b) 1
c) 3
d) -3
Explanation: For a lossless antenna the whole peak power is radiated towards the receiver without any losses. So the antenna efficiency will be 100% so it is 0dB.

14. Relation between Antenna gain G and directivity D is ______
a) G = ∈r D
b) G = ∈r/D
c) G = D/∈r
d) G = 1/∈rD
Explanation: Antenna gain refers to the amount of radiation intensity in the desired direction to that of would have radiated when the isotropic antenna radiates. The relation between Antenna gain and Directivity is G = ∈r D, ∈r is the antenna efficiency.

15. What is the antenna efficiency if the gain equals to the directivity of the antenna?
a) 1
b) 0
c) 3
d) 2
Explanation: The relation between Antenna gain and Directivity is G=∈r D, ∈r is the antenna efficiency.
⇨ ∈r= GD=1

16. Which of the following method is employed for the gain transfer method for antenna outdoor range?
a) Anechoic chamber
b) Tampered chamber
c) Reflection range
d) Compact range
Explanation: Free space or elevation or Reflection range can be employed for the gain transfer method. Anechoic, tampered chambers and compact ranges come under indoor ranges. In gain transfer method the unknown gain antennas are compared with the standard gain antennas.

17. In which of the following type of measurement prior gain knowledge of antennas used in measurements is not necessary?
a) Absolute gain
b) Gain transfer method
c) Gain compromise method
d) Both gain transfer and absolute gain method
Explanation: In absolute gain method, the prior knowledge of gain of antennas used in the measurements is not necessary. Gain transfer or Gain compromise method requires the standard gains of the antennas used for measurements to compare the AUT.

18. Ground wave is always __________ polarized.
a) Vertically
b) Horizontally
c) Either vertical or horizontal
d) Neither horizontal nor vertical
Explanation: If the wave is horizontally polarized, then the electric field is short circuited by the earth. So the ground wave is always vertically polarized and vertical antennas are used.

19. Ground wave propagation is used for signals up to frequency __________
a) 2MHz
b) 2GHz
c) 30MHz
d) 30GHz
Explanation: Ground wave propagation is used for signals up to frequency of 2MHz. Ground waves are vertically polarized and transmitting and receiving antennas are placed closely and the wave follows the curvature of the earth.

20. The broadcast signals received at low frequencies during day-time are due to _________
a) Ground wave
b) Space wave
c) Sky wave
d) Tropospheric waves
Explanation: Ground wave propagation is used for signals up to frequency of 2MHz. It is useful for the broadcast and low frequency signals. Space waves are also known as tropospheric waves useful for FM reception. Sky wave propagation is used for long distance communication.

21. Ground wave propagation is also known as _________
a) Surface wave
b) Tropospheric wave
c) Ionospheric wave
d) Stratospheric waves
Explanation: Ground waves are also known as Surface waves as the wave propagates close to the surface of earth. Space waves are known as tropospheric waves and Sky waves as Ionospheric waves.

22. The ground wave propagation uses horizontal polarized antennas
a) True
b) False
Explanation: If the wave is horizontally polarized, then the electric field is short circuited by the earth. So the ground wave is always vertically polarized and vertical antennas are used.

23. Which of the following is particularly used for VLF?
a) Surface wave
b) Tropospheric wave
c) Ionospheric wave
d) Stratospheric waves
Explanation: Ground waves are also known as Surface waves are used for low frequencies and broadcasting. Tropospheric waves are used for Mf and HF signals. Ionospheric waves are used for long distance communications.

24. Ground wave field strength is given by E= _________
a) AEo/d
b) A(Eo)2/d
c) dEo
d) AEo/d2
Explanation: The ground wave field strength at a point E=AEodV/m
Where Eo is field strength of wave at unit distance from transmitting antenna
A is factor of ground losses
D is distance of point from Transmitting antenna.

25. Which of the following propagates by gliding over the surface of earth?
a) Surface wave
b) Tropospheric wave
c) Ionospheric wave
d) Stratospheric waves
Explanation: Ground waves are also known as Surface waves. Ground waves are vertically polarized and transmitting and receiving antennas are placed closely and the wave follows the curvature of the earth.

26. How the ground wave losses vary with high frequencies?
a) Increases
b) Decreases
c) Does not depend on frequency
d) Increase or decrease
Explanation: Ground wave propagation is used at below 2MHz frequency. Ground wave propagation is used for short distance. By using sufficient power and low frequencies it can be used effectively. Ground wave losses increase rapidly with frequencies.

27. The electric field of the component increases in ground wave when it tilts more at the surface.
a) True
b) False
Explanation: As the wave front tilts more and more towards the surface then the electric field gets short circuited. As it gets reduced with tilt, at some point it is completely attenuated.

28. Up to which frequency the ground wave propagation is used?
a) 2MHz
b) 2GHz
c) 30MHz
d) 30GHz
Explanation: Ground wave propagation also known as surface wave propagation is used up to 2MHz. sky wave propagation is used at 2MHz to 30MHz.

29. In a ground wave propagation, which component of electric field is short circuited when it’s in contact by earth?
a) Horizontal
b) Vertical
c) Both horizontal and vertical
d) Neither horizontal nor vertical
Explanation: Any horizontal component of electric field which is in contact with earth is short circuited by earth. Usually ground wave propagation is done by vertical antennas so it is vertically polarized.

30. During ground wave propagation earth behaves like a __________
a) Leaky capacitor
b) Leaky Inductor
c) Series combination of capacitor and inductor
d) Parallel combination of capacitor and inductor
Explanation: Any horizontal component of electric field which is in contact with earth is short circuited by earth. So earth behaves like a leaky capacity. It forms a resistor in shunt with a capacitor.

31. Sky wave propagation reflects the frequencies ___________
a) 2MHz
b) 2 MHz to 30MHz
c) 2 GHz to 30 GHz
d) 30 GHz to 50GHz
Explanation: Ground wave propagation also known as surface wave propagation is used up to 2MHz. sky wave propagation is used at 2MHz to 30MHz.

32. At what distance the sky wave propagation is present from the earth surface?
a) 50 to 400km
b) Below 50 km
c) 600 to 750km
d) 50 to 400 m
Explanation: Sky wave propagation also known as ionosphere propagation reflects the waves with frequency 2 to 30MHz. It is present at 50 to 400km from earth surface.

33. Space wave propagation reflects the waves with frequencies _________
a) Below 2 GHz
b) 2 to 30MHz
c) Above 30GHz
d) Above 30MHz
Explanation: Ground wave propagation also known as surface wave propagation is used up to 2MHz. sky wave propagation is used at 2MHz to 30MHz. Space wave propagation reflects frequencies above 30MHz.

34. Space wave propagates at which frequency band?
a) VHF
b) HF
c) MF
d) EHF
Explanation: Space wave propagation reflects frequencies at 30 to 300MHz range. So it propagates at VHF band.
MF- 300 KHz – 3MHz
EHF- 30GHz-300GHz

35. Communication through LOS can be increased by decreasing the height of antenna.
a) True
b) False
Explanation: Line of sight provides a direct communication link from transmitter to receiver. If the height of antennas is increased then the LOS is also improved.

36. In which of the following mode of propagation the waves are guided along the surface of the earth?
a) Ground wave
b) Sky wave
c) LOS
d) Space wave
Explanation: In ground wave or surface wave propagation the waves are guided along the surface of the earth. In sky wave they are reflected at different layers in the ionosphere. Space wave uses either direct or indirect method of propagation from transmitter to receiver directly.

37. In which of the following modes of propagation the ionosphere acts as the reflecting surface for the waves?
a) Ground wave
b) Sky wave
c) Space wave
d) LOS
Explanation: In Sky wave or Ionospheric wave propagation waves are reflected from the ionosphere layers depending upon different frequencies.

38. Which of the following statement is defined as line of sight distance?
a) Distance covered by a direct space wave from transmitting to receiving antenna
b) Distance covered by an indirect space wave from transmitting to receiving antenna
c) Distance covered by a direct sky wave from transmitting to receiving antenna
d) Distance covered by an indirect sky wave from transmitting to receiving antenna
Explanation: LOS (Line of sight) is defined for space wave propagation. It is the distance covered by a direct space wave from transmitting to receiving antenna. It depends on the height of the transmitting and receiving antennas and effective earth’s radius factor k.

39. On which of the following factors does the LOS distance depends?
a) Height of receiving antenna alone
b) Height of transmitting antenna alone
c) Only on height of transmitting and receiving antenna
d) On height of transmitting and receiving antenna and effective earths radius factor k