If you're not getting a picture from your satellite connection, determining the condition of your satellite dish requires a process of elimination. The amplifier/down-converter located in the feed horn of the antenna may be bad, but to test it requires taking it to a repair shop. Before doing that, you should eliminate all other possibilities to avoid unnecessary time and expense. You must subscribe to a satellite service and have a receiver to get a signal.
Turn on your satellite receiver and your TV. Make sure your TV input selector is set for the input where you are connected. If you don't see a picture at all, check the cables between the receiver and the TV. If they are good and you still see no picture at all, your receiver is bad and you must get it fixed before you can check your dish. If you see a warning that you have no receive signal, your receiver is OK and you can continue checking.
Look outside at the weather. A heavy thunderstorm between your dish and the satellite may cause a temporary loss of signal, even though it may not be raining where the dish is located. If there is a storm, wait until it passes.
Look at your satellite dish to see if it may have been knocked out of position by a heavy wind or a falling object. If the dish seems to be out of position but not broken, call your satellite company to have it aligned. If it is bent or the feed horn is bent or broken, the dish is bad. Look from the dish in the direction of the satellite to make sure no trees have grown into the path, or new houses or buildings have blocked the signal.
Look at the cover on the feed horn to see if it is cracked or broken. Water or moisture inside could damage the LNB. Some have a translucent cover that may show condensation on the inside that could cause a failure.
Check the cable connections at the receiver and the dish. Remove them and look for a bent or broken center conductor, a damaged connector that doesn't make a ground connection, or dirt or corrosion that could block a signal. Replace any bad connectors or call your satellite service company to do it.
Check the cable for cuts, breaks or crushing. Follow it for its entire length and look carefully. A crushed cable could have the center conductor shorted to the shield and block the signal. If the cables and the receiver are OK, and the dish is properly aligned and not physically damaged or blocked, you probably have a bad LNB in your dish and it needs to be replaced.
If your dish is in a location difficult or dangerous to access, call your satellite company to do the inspection. Don't take unnecessary risks.