Question

The length of half-wave antenna is at 30 MHz

A. 2.5 meter

B. 5 meter

C. 10 meter

D. 100 meter

Answer 1

$\begin{aligned} f &= 30\ MHz = 30 × 10^6Hz \\ &= 3 × 10^7 Hz \end{aligned}$

$c = 3 × 10^8 ms^{-1}$

from,

$c = f\lambda$

$\lambda = \frac{c}f$

$\lambda = \dfrac{3×10^8}{3×10^7} = 10m$

length of half-wave dipole = $\frac{10}{2}m = 5m$

Therefore, the length of half-wave antenna is 5m (B.)