Question

Assuming the loss resistance of a half-wave dipole antenna to be negligibly small and ignoring the reactance component of its antenna impedance, calculate the standing wave ratio on a $50\Omega$ transmission line connected to the dipole antenna.

• A. 1.96
• B. 3.5
• C. 1.46
• D. 2.56

Answer 1

The correct option is C 1.46

A half wave dipole has a radiation resistance of $73\Omega$. To the transmission line this behaves as a load so, the reflection coefficient is

$\Gamma =\frac{R_{rad}-Z_0}{R_{rad}+Z_0}=\frac{73-50}{73+50}=0.187$

$\therefore$ Standing wave ratio $S=\frac{1+|\Gamma |}{1-|\Gamma |}=\frac{1+0.187}{1-0.187}$

$=1.46$