Question 11 : What is the full form of LPDA?
1. Log Periodic Dipole Array
2. Log Periodic Dispersed Array
3. Low Periodic Dispersed Array
4. Low Power Dipole Array
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Question 12 : Field strength at a distance from an antenna is measured with __________
1. a slotted line
2. a dipole
3. an EIRP meter
4. a field strength meter
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Question 13 : An ungrounded antenna near the ground ________
1. must be horizontally polarized
2. acts as an antenna array
3. is unlikely to need a ground screen
4. acts as a single antenna of twice the height
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Question 14 : Which of the following antennas is best excited from a waveguide?
1. Marconi
2. Horn
3. Helical
4. Discone
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Question 15 : Which one of the following reasons for the use of a ground screen with antennas is false?
1. Impossibility of a good ground connection
2. Provision of an earth for the antenna
3. Protection of personnel working underneath
4. Improvement of radiation pattern of antenna
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Question 16 : Which is the standard reference antenna for the directive gain?
1. Isotropic antenna
2. Marconi antenna
3. Helical antenna
4. Log Periodic antenna
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Question 17 : The radiation of energy from an antenna can be seen in the ________
1. standing wave around antenna
2. radiation resistance of the antenna
3. reflected resistance of the antenna
4. I2R loss of the antenna
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Question 18 : AM waves is represented by E_t cos? ?_c t. What does E_t denotes?
1. amplitude of modulated wave
2. amplitude of carrier signal
3. amplitude of modulating signal
4. amplitude of message signal
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Question 19 : What is the front to back ratio of a half wave dipole antenna?
1. 0 dB
2. 10 dB
3. 100 dB
4. 50 dB
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Question 20 : An antenna's beamwidth is measured ________
1. from +90° to -90°
2. between half power points
3. between the minor side lobes
4. between the major side lobes
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