A 50 MHz sky wave sky wave takes 4.04 ms to reach a receiver via re-transmission from a satellite 600 km above earth's surface. Assuming re-transmission time by satellite negligible, find the distance between source and receiver. If communication between the two was to be done by Line of sight (LOS) method,what should be the size of transmitting antenna ?

Options

A. 606km
B. 170km
C. 340km
D. 280km

Answer

B

Explanation

Here Total time taken, `t=4.04 ms=4.04xx10^(-3)s` Let x be the distance satellite from the surface of earth
Total time taken (t)`=("Total distance travelled"(2x))/("Speed of electromagnetic waves"(c))`
` therefore x=(ct)/(2)=((3xx10^(8))(4.04xx10^(-3))/(2)=6.06xx10^(5)m=606km`
`therefore x=(ct)/(2)=((3xx10^(8))(4.04xx10^(-3)))/(2)=6.06xx10^(3)m=606km`
Let T be the source of electromangetic waves (i.e. transmitter), R be receiver and S be sate as shown in figure.

`d^(2)xxx^(2)-h^(2)=(606)^(2)-(600)^(2)`
`therefore d= 85.06km`
Distance between source and receiver
`=2d=2xx85.06=170km `