A communication link at a frequency of 30 MHz uses a half-wave dipole for the transmitting antenna and a small loop (directivity equal to 1.5) for the receiving antenna, involving a distance of 100 km. The antennas are oriented so as to receive maximum signal and the receiving antenna is matched to its load. If the received time-average power is to be 1μW, find the minimum required value of the maximum amplitude I0 of the current with which the transmitting antenna has to be excited. Assume the antennas to be lossless.