Yagi antennas are a specific type of antenna construction.
you take a dipole antenna and multiply that by 2 or more, all mounted on a pole, one element in front of the other.
they look like herringbone and the more elements, the more narrow the beam is, and the more gain.
i remember seeing those large directional antennas on some roofs, and they were very large because of the frequencies involved:
a half wave is around 18 Ft.
some parabolic antennas are a kind of cousin of those Yagis;
they have a halfwave dipole and behind them a huge reflector to direct the waves to the dipole, like a very large optical magnifier concentrating light in a very small spot.
CB'ers also used another kind of high gain antenna, but i can't remember the name.
