Question

What is the maximum power gain when the radiation resistance is 72Ω, loss resistance is 8Ω and the maximum directive gain is 1.5?

(a) 1.15

(b) 1.35

(c) 1.25

(d) 1.53

Answer 1

Right answer is (b) 1.35

For explanation: Maximum power gain Gpmax=ηr Gdmax

Radiation efficiency ηr=(frac{R_r}{R_r+R_l}=frac{72}{72+8}=frac{72}{80}=0.9)

Now, Gpmax=ηr Gdmax=0.9×1.5=1.35