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The larger the dish, the stronger is the signal you could receive, that is, the less intermittent is the picture. However, the risk of wind disturbance, cost, and space is proportionally higher. There are two bands of microwave signal normally used for TV. C band is the older generation; it requires a huge dish. Ku band is the modern generation, requires a smaller dish. Many pay TV provide you strong signal by aiming at a smaller coverage area, such that a smaller fixed position dish is good enough. For FTA signal, because of broadcaster is aiming at larger coverage area, so you must use a bigger dish than those pay TV. You might found that not all stations on the same satellite are equal. Different transponder on same satellite can give different signal quality. It is very depending on how much power that transponder is transmitting and which coverage area it is pointing to. Satellite is using solar energy. Power is precious in space.
Depending on how far you are away from the equator. We recommend 39h or 100cm dishes. This is the biggest dish size, which can be driven by a standard sized rotor. For northern or southern territory, you might need even bigger dish.
The actual size of the dish is very often exaggerated. Many dishes are oval shaped. The dimension given is based on the longest measurement. A round dish with same size rating of oval shape dish has more area. Some manufacturers use the curvature as measurement. The size claim could be boasted by three inches. We found that every 3 inches increment gives significant improvement on performance. Same size dishes made by different manufacturer can give observable differences on reception because of the real size is different. Do not trust the dimension claimed by manufacturer. You must compare it with your own measurement.
The atmosphere can attenuate signal. The shortest route of air traveled is directly under the equator. When you are away from the equator, the signal has to travel a thicker air. When the satellite is located at the same longitude with you, it has the shortest air path to your site. When you point your dish to another satellite, which is further away from your longitude, your air path is longer. The signal attenuation is proportional to the air path. Cloud, rain, and snow can weaken your signal. Wind can cause temporary off alignment of dish. The dish is never too big. You could receive the signal well on new installation. Your dish could be off aligning after some severe weather. This is especially troublesome on small dish because it is touchy on alignment. Our experience shows that weather is not a major factor of poor reception. Dish size plays a more important role.
Besides the dish, you need a good rotor if you want to receive multiple satellites, unless you want to install several dishes. Some rotor has a weak motor. You might have to push it to get moving. USALS compliance is a good feature to select. Theoretically is supposed to use two motors to control the dish. One motor rotate horizontally, and the other vertically. Since the vertical rotation always follows a fixed geometrical pattern. By using a tilted shaft rotor, we can eliminate the vertical motor.
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