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1.	If beam efficiency is 0.87 then the stray factor is ____(a) 1.87(b) 0.13(c) 1.30(d) 0.87I got this question in an international level competition.This intriguing question comes from First Null Beam Width in section Antenna Beam Width & Input Impedance of Antennas
Answer» CORRECT answer is (B) 0.13 To EXPLAIN: Stray FACTOR ∈s is the ratio of minor BEAM area to total beam area. Given beam efficiency ∈B=0.87 ∈B+∈s = 1 ∈s = 1-0.87 = 0.13

2.	What is the Beam area in radians when the HPBW in perpendicular planes are given by 60°, 30°?(a) \(\frac{\pi^2}{8}\)(b) \(\frac{\pi}{2}\)(c) \(\frac{\pi^2}{18}\)(d) 2This question was addressed to me by my school teacher while I was bunking the class.The question is from Half Power Beam Width topic in chapter Antenna Beam Width & Input Impedance of Antennas
Answer» Right option is (c) \(\frac{\pi^2}{18}\) Easy explanation: Beam AREA B=θE θH=60°×30°=\(\frac{\pi}{3}×\frac{\pi}{6}=\frac{\pi^2}{18}\)

3.	Find the directivity when the half power beam widths are 45° and 60° in perpendicular planes.(a) 12.58(b) 17.98(c) 22.91(d) 15.28The question was asked during an internship interview.This interesting question is from Half Power Beam Width in portion Antenna Beam Width & Input Impedance of Antennas
Answer» The CORRECT option is (d) 15.28 Easy explanation: DIRECTIVITY in TERMS of HPBW (in degrees) is given by \(D=\frac{41257}{θ_E θ_H} =\frac{41257}{45° × 60°}=15.28\)

4.	Beam width is the measure of directivity of antenna in terms of angles either radians or degrees.(a) True(b) FalseThis question was addressed to me in an interview for internship.The query is from Half Power Beam Width in section Antenna Beam Width & Input Impedance of Antennas
Answer» Right choice is (a) True The best explanation: BEAM width is defined as the measure of angular width at two POINTS on the major LOBE where the power decreases to half of the maximum radiated power. So beam width is the measure of directivity of ANTENNA. \(D=\frac{4\pi}{B}\)

5.	Beam area and directivity are related as _____(a) \(D=\frac{2\pi}{B}\)(b) \(D=\frac{4\pi}{B}\)(c) \(D=\frac{B}{2\pi}\)(d) \(D=\frac{B}{4\pi}\)I have been asked this question in a job interview.My question comes from Half Power Beam Width in section Antenna Beam Width & Input Impedance of Antennas
Answer» Right option is (b) \(D=\frac{4\pi}{B}\) The EXPLANATION: BEAM width/ beam AREA is the measure of DIRECTIVITY of an antenna. \(D=\frac{4\pi}{B}\)

6.	Relation between beam efficiency and stray factor is given by ____(a) ∈B+∈s=1(b) ∈B-∈s=1(c) \(\frac{\in_B}{\in_s}=1\)(d) ∈B+∈s=2The question was asked during a job interview.This intriguing question comes from First Null Beam Width in chapter Antenna Beam Width & Input Impedance of Antennas
Answer» The correct CHOICE is (a) ∈B+∈s=1 Best explanation: Stray factor ∈s is the RATIO of MINOR BEAM area to total beam area. Beam efficiency ∈B is the ratio of major beam area to total beam area. Total beam area is sum of major lobe area ΩM and minor lobe area Ωm. \(\in_B=\frac{\Omega_M}{\Omega_A}, \in_s = \frac{\Omega_m}{\Omega_A}\) ∈B+∈s=1

7.	If the antennas revolution time is 10 sec and 3 dB beam width duration is 150ms then the antenna beam width is _______(a) 5.4°(b) 54°(c) 15°(d) 1.5°I had been asked this question in an online interview.I want to ask this question from First Null Beam Width topic in section Antenna Beam Width & Input Impedance of Antennas
Answer» The CORRECT ANSWER is (a) 5.4° Explanation: Antenna beam width = \(\frac{Beam \,DURATION}{rotating \,PERIOD}×360° = \frac{150m}{10} ×360°=5.4°\)

8.	If the HPBW is 30° then FNBW is approximately _____(a) 60°(b) 30°(c) 15°(d) 20°The question was posed to me during an online interview.My question is taken from First Null Beam Width in chapter Antenna Beam Width & Input Impedance of Antennas
Answer» The CORRECT ANSWER is (a) 60° For EXPLANATION I WOULD say: FNBW ≈ 2HPBW=2×30°=60°

9.	Total beam area is sum of major and minor lobe areas.(a) True(b) FalseI got this question in an internship interview.My enquiry is from First Null Beam Width in chapter Antenna Beam Width & Input Impedance of Antennas
Answer» The correct choice is (a) True The EXPLANATION is: Total BEAM area is sum of major LOBE area ΩM and MINOR lobe area Ωm. ΩA = ΩM+Ωm

10.	Half-power beam width is also called as 6-db beam width.(a) True(b) FalseThis question was addressed to me by my college professor while I was bunking the class.Question is taken from Half Power Beam Width in chapter Antenna Beam Width & Input Impedance of Antennas
Answer» Correct answer is (b) False The explanation is: Half-POWER beam width is also CALLED as 3-db beam width. It the angular width calculated between the POINTS when the power DROPS to half of the MAXIMUM power radiated.

11.	What happens to the beam-width of antenna if the frequency of operation is increased?(a) Beam-width will decrease(b) Beam-width will increase(c) Beam-width is independent of frequency(d) Beam width may increase or decreaseThe question was posed to me in a job interview.This intriguing question comes from Half Power Beam Width topic in division Antenna Beam Width & Input Impedance of Antennas
Answer» The correct OPTION is (a) Beam-width will decrease Explanation: If frequency is high, power RADIATED is low (From Radar range equation). That MEANS directivity is high as \(D=\frac{4\pi U}{P_{rad}}.\) Beam width and directivity are INVERSELY proportional to each other. So beam width will be low.

12.	Angular width between the first nulls or first side lobes is called as _______(a) half power beam width(b) full null beam width(c) beam area(d) directivityThis question was addressed to me in an interview for internship.My question comes from First Null Beam Width topic in section Antenna Beam Width & Input Impedance of Antennas
Answer» Correct option is (B) full null beam width Easy explanation: Angular width between the first nulls or first side LOBES is called full null beam width. Half power beam width is the angular width measured between the 3DB power POINTS of the major lobe. Beam area is the product of HPBW in perpendicular directions. Directivity is the maximum DIRECTIVE gain.