prime focus antenna (PFA)
A prime focus antenna(PFA) is a parabolic antenna. It has the shape of a paraboloid, is circular, completely symmetrical in design and the focal point of the reflector dish is exactly in the center of the dish.
In contrast to central antennas, the center of the dish of offset antennas is not centrally located in the middle, but is slightly offset. The LNB converter attached to the feed horn is located at this point. The reflector reflects all radio beams hitting the reflector in the feedhorn.
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The orientation of prime focus antennas corresponds to the line of sight to the satellite. This means that the PFA antenna is arranged in a relatively open position, which can cause snow to accumulate in the reflector dish in winter and change the reception characteristics. In addition, the radiator, which is located exactly in the center of the dish, shades the main beam direction.
PFA antennas include the double reflector parabolic anten nas such as the Gregory antenna and the Cassegrain antenna.