Question
A ground receiver station 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.
(Given the value of radius of the earth is 6400 km and maximum electron density, Nmax = 1012 m-3).
Solution
Given,
Height of the ground transmitter = 300 m
Range of transmission = 100 km
Maximum distance covered by space wave propagation is,
As receiver-transmitter distance is 100 km, so space wave propagation is not possible for both 5 MHz and 100 MHz waves.
Critical frequency for ionospheric propagation is,
As frequency (5 MHz) of signal is less than the critical frequency, hence, this signal comes via ionospheric mode while signal of frequency 100 MHz is transmitted through the satellite mode.
