All antennas have certain general properties which apply both to receiving and transmitting modes.
Thus, the more efficient the antenna is for transmitting, the more effective it is for receiving. Even so, the concept of reciprocity be- tween transmission and reception still stands correct. It is reasonable to expect the largest amount of current that can be achieved from the power available will provide the best radiation from a given antenna. The greatest amount of current flows when ii the reactance of the antenna is cancelled and the an- tenna made resonant at the operating frequency. The i shortest conductor that will be self-resonant at a given frequency is one that is about half as long as the size of the radio wave.