Field and Wave Electromagnetics 2nd Edition by David Cheng

Exercise 40

A transmitting vertical half-wave dipole 60 (m) above the ground radiates 400 (W) at 100 (MHz). Assume the ground to be perfectly conducting.
a) Calculate the power available at a vertical half-wave receiving antenna 50 (km) away at a height 30 (m) above the ground.
b) At a distance 50 (km) from the transmitting antenna, where (at what altitudes) would there be a null field