Plug an analog cable line into your tv. Watch the picture on channels 4 thru 6 and then 14. I am almost definite you will see a white line go from top to bottom on your screen! Flashing intermittently. If you see this book another service call and show the tech. And inform him to let his main. Tech know that there is a faulty AGC on your leg of the distribution. You can see that your SNR drops into the noise floor on US 3. And your signal levels are very low and drop even lower. As a tech when you see this kind of movement in the span of an hour and at that frequency. I would always say AGC.
Would a TV card work? We got rid of our last analog TV over a year ago so we don't have any other TV to try.
Sure would! As long as it has a coax spigot on it you will see the analog