Originally Posted by LeoDLion
After seeing this problem for a month, it went away. Nothing to do with my system at home. It must have something to do with the head office broadcast. The sad thing is Comcast's standard procedure is to send a tech to your house.
There must be a way of checking the signal at the source. I sent an email to Comcast about this. What is the chance somebody will do something about it?
Why do you conclude that the problem must be at the head office broadcast?
The cable plant is a huge infrastructure. Signals pass through many cables, connectors, splitters, amplifiers, and who knows what-all between the main office and your living room. Every point along the transmission path is a vulnerability that could allow signal degradation to occur if damaged or compromised. Even if the infrastructure is physically intact and undamaged, there are adjustable elements (amplifiers/attenuators) in the path to ensure signals reach end users within signal strength tolerances, and if those are not set properly you can see problems.
If you had a problem and it went away, it's far more likely that there was an issue somewhere in the plant between the main office and your house, and it got fixed without you knowing about it. Another possibility is that your problem is related to environment, and that it will recur when the same environmental conditions (heat, wet, etc.) exist again at the vulnerable point.
The reason they roll a truck is because the vast majority of the time, picture quality issues are somewhere downstream in the cable plant, and the best way to troubleshoot that is to start at the end and work backward up the line. When 100 people from a small area call with the same problem, they start looking at the local distribution network in that area. When 10,000 people from a wide area call at the same time with the same complaint, that's when they start looking at the source instead of the receiving end.