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Here are a few additional items. The polarization is controlled by the feed. The dish can be a skeleton type with wires and work almost as well as a solid metal but with much less wind loading. That is if the wires are the same direction as the feed polarization.
Usually waveguide feed in Parabolic Dish. the Polarization direction
Is the same as the direction of the input connector. If the connector perpendicular to ground. the polarization Vertical . if you need horizontal polarization. Just rotate the dish with the feed 90°. And that Only if you have symmetric dish.
Usually waveguide feed in Parabolic Dish. the Polarization direction
Is the same as the direction of the input connector. If the connector perpendicular to ground. the polarization Vertical . if you need horizontal polarization. Just rotate the dish with the feed 90°. And that Only if you have symmetric dish.
hmmmm.... i don't agree.
For my opinion, the words "vertical" and "horizontal" are relatet to the "orientation" of the E vector with respect the horizont.
The definition is needed for estabilish a communication path; but this definition contain a little misleading, so require that people working at the TX and RX station be sinergic.
In fact, what does "vertical" mean? Think a parabolic antenna with AZ-EL movement capability looking at the meridian position and observing a satellite. Mount the horn according to the "vertical" definition. Now move the AZ, step by step, tracking a star (or some types of satellites) up to it will be set. At that position the TX polarization will be swapped! But the received polarization still remain the same! This non happen using the circular polarization.
This is the main reason why in Radioastronomy and often in satellite communication the circular polarization is used.
In any antenna, the feed (primary radiator) determines the polarization of a complete antenna. Some antennas, like for satellite communication, can utilize two orthogonal polarizations, some even both at once (VSATs).
In any communication link, a transmitting antenna and an opposite receiving antenna should be set to the same polarization for the best transmission.
The difference between the polarizations is that if one of the pair of antennas is set to the orthogonal one, the transmission is suppressed by "polarization rejection", typically >20 dB. This effect is often used for frequency sharing between close links. Circular polarization is used e.g. in satellite communication to avoid fine adjustments that depend on station latitude. Frequency sharing is used there to multiply programming availability.
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