Field and Wave Electromagnetics 2nd Edition by David Cheng

Exercise 69

The transmitting antenna of a radio navigation system is a vertical metal mast 40 (m) in height insulated from the earth. A 180 (kHz) source sends a current having an amplitude of 100 (A) into the base of the mast. Assuming the current amplitude in the antenna to decrease linearly toward zero at the top of the mast and the earth to be a perfectly conducting plane, determine:
a) the effective length of the antenna,
b) the maximum field intensity at a distance 160 (km) from the antenna,
c) the time-average radiated power,
d) the radiation resistance.