Reflector antenna

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Radio waves will reflect off of a large conducting plane as if it was a mirror. A coarse screen will work just as well. The reflector eliminates most reception from the rear while at least doubling the forward gain. Reflector antennas are very common.

The screen reflector shown above has the gain of about 4 dipoles. The parabolic reflector focuses the signal onto a single dipole, but its bandwidth is a little disappointing. The corner reflector has a little less gain but much greater bandwidth. The corner reflector has roughly the gain of three dipoles. It is a good medium gain antenna, widely used for UHF. If you need more than 25 dBi then the paraboloid dish is the only practical choice, but for VHF or UHF they are huge.