Question

If beam efficiency is 0.87 then the stray factor is ____

(a) 1.87

(b) 0.13

(c) 1.30

(d) 0.87

I 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 1

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