A ground receiver station is receiving a signal at 8 MHz , transmitted from ground transmitter at a hight of 289 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 10^6m`. Maximum number density of electrons in ionosphere `= 10^(12)m^(-3)`.

Explanation

Here, ` h = 289 m, R = 6.4 xx 10^(6) m, N_(max) = 10^(12) m^(-3)`.
For space wave propagation, maximum distance covered is given by
`d = sqrt (2Rh) = sqrt(2 xx (64 xx 10^6) xx 289) = 60.83 xx 10^(3) m ~~ 61 km`
Since the distance between transmitter and receiver is 100 km, hence for the given frequency signal of 8
MHz, the propagation is not possible via space wave propagation.
For sky wave propagation, the critical frequency
`v_c = 9(N_(max))^(1//2) = 9 (10^12)^(1//2) = 9 xx 10^6 Hz = 9 MHz`
Snce the frequency of signal 8 MHz is less than `v_c`, hence its propagation via sky wave is possible.