A satellite dish is parabolic in shape in order to focus the signals on one point. The surface contour must be accurate to within 3mm or it will not function correctly. This is important as the power transmitted by satellites is very small, and the signals received on earth are considerably smaller, therefore the satellite dish needs to be very efficient and have as high a gain as possible.
There are four main types of satellite dish:
- Prime Focus – This is the simplest type of dish, where the LNB (Low Noise Block) is situated in the front middle of the dish and it is beamed directly at the satellite.
- Cassegrain – This is similar to the prime focus dish, but in this case the LNB is situated behind the dish in the middle. The signals are focussed onto the LNB using a small reflector on the front middle of the antenna.
- Offset – The offset dish is the most popular type used in installations all over the world. With this type of dish the LNB is located at middle bottom of the dish so it is not in front of the received signal. This improves the efficiency of the dish.
- Gregorian – This is a version of the offset dish which uses a small reflector to reduce the size of the boom arm which holds the LNB.
« Go to the Home Page