When a radio wave hits an antenna, the electrical component of the wave induces a difference of potential in the conductor which gives rise to an electric current. This is called electromotive force. The current induced is normally small, therefore, we usually design antennas to be as efficient as possible.
Ways to increase efficiency:
- Ensure that the impedance of the antenna matches what it's hooked up to.
- Cap the ends of the antenna with an insulator
- If there is a power line nearby, run the antenna at a right angle to that wire to decrease interference.
- Make the antenna resonant at the frequency you're interested in. You can do this by adjusting the length of the wire, inductance, capacitance.
- Design the antenna so that it focuses the energy from the direction you care about, as opposed to listening equally in all directions.
