A ground reciever is receiving a signal at (a) 5 MHz, and (b) 100 MHz, transmitted from a ground transmitter at a height of 300 m located at a distance of 100 km, Identify whether it is coming via space wave or sky wave propagation or satellite transponder. [Radius of earth `~~ 6.4 xx 10^(6) m , N_(max)` of ionosphere `= 10^(12) m^(3)`]

Options

A. Space wave
B. Sky wave propagation
C. Satellite transponder
D. All of these

Answer

b

Explanation

Maximum distance covered by space wave communicatiion `sqrt(2Rh)=62km`
critical frequency `=f_(c)=9(N_(max))^(1//2)~=9MHz`
`5MHz lt f_(c)`, sky-wave propagation (ionospheric propagation)