Question

If critical frequency for ionosphere is 30MHz. Calculate the maximum frequency which can come back on earth if transmitted at an angle ${60}^0$ from vertical position:

• A. 30MHz
• B. 60MHz
• C. 40MHz
• D. 15MHz

Answer 1

Answer: (B)

60MHz

Relation between Maximum frequency if transmitted at angle $\theta$ and critical frequency is given by :

$f_{max}=\frac{f_c}{\cos \theta }$

Here $\theta ={60}^o$ and $f_c=30MHz$

$f_{max}=\frac{30MHz}{\cos {60}^o}=60MHz$

So the maximum frequency is 60MHz , option B is correct