1. What is the radiation pattern of a Yagi-Uda antenna?
a) Broad-side
b) End-fire
c) Collinear
d) Both Broadside and End-fire
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.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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.
7. 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.
8. 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.
9. Which of the following antenna belongs to rectangular aperture?
a) Horn antenna
b) Helical antenna
c) Parabolic antenna
d) Conical antenna
Explanation: The aperture of antenna at the end determines its shape. Horn antenna has a rectangular aperture. Helical, Parabolic, conical antenna have circular apertures. Helical antenna belongs to frequency independent antenna.
10. The radiation pattern of rectangular is similar to line source integrated in two directions
a) True
b) False
Explanation: The radiation pattern for the rectangular distributions is similar to the line source distributions. In this the patterns is calculated by integration in two directions as rectangle have two different lengths in different direction.