Donald,
Dish alignment is typically the culprit, but there can be many issues at hand here. A poor cable connection or a bad cable fabrication, weather related issues, a failing switch or a failing LNBF (very rare) or a few other items that are probably too rare to start off discussing.
Always make sure that you tackle and address the most simplest items first when troubleshooting these issues. If you have any type of switch in your circuit, bypass it (use a barrel connector and simply take a detour around the switch). Recheck your quality level after the switch has been elliminated from the circuit.
Second step, check all your cable ends and make sure they are good. If you are in doubt, redo your connector installations. Poor connector fabrication and moisture entry are a common failure, but fairly easy to repair.
Next check your dish alignment, but don't readjust it just yet. Have someone assist you or if you have nice weather, take portable TV and the receiver right out to your dish and then you stand behind the dish and grasp the edges with both hands and very gently pull and push on the dish to move its postion up, down or left and right and see if the signal Q improves for you.
Don't twist the dish or put enough pressure on it to bend the dish refelector, just some very light pressure is all that is required. Push on one side of the dish while pulling on the other side, just be very gentle. Like you were showing off a flower blossom to your grandmother. GENTLY.
If you rule out the cables and connectors and switches, and you get positive results through flexing the dish, then your alignment is probably at fault. If you had a good signal initially, but it has been dropping over a short period, check your dish and motor fasteners and your mast for some bolt that is loose and is moving. Especially if you have had some windy days recently or at least since you have observed the signal dropping.
RADAR