Hello, I'm TV Tech1 and I'll be working with you to identify and help you resolve your problem.
Q stands for Signal Quality and L stands for Level or signal level. If your LEVEL is bouncing between 0 and 99% all the time, I would suspect that either your LNA on your satellite dish is bad, or you're not getting the DC voltage to your LNA from the satellite box. That can be related to the rest of the cable you didn't replace or any of the connectors on the end of the coax.
How to know for sure? Well, you did have to replace the "perished" cable section and that means the whole system outside has some serious wear and tear to it....The plastic covers on the LNA protect it from moisture, and usally keep bees from nesting inside it...but they do become brittle and crack, just like cables do.
Overall, I would seriously replace BOTH the LNA and the RF coaxial cable on the outside of the house, just to get them back up to normal operation. If you have splitters on the outside of your home (you do have two boxes, and both are affected so you do have a splitter on the output side of the LNA) I would start there and unscrew the connections, and plug them back in about 10 times to knock any corrosion off the contacts and the RF cable's center wire.
I would do the same thing on the LNA connector(s) While you are there doing that, just how "Flexible" is the plastic cover on the cable? Is it soft and flexible or Brittle and stiff?
Remember how your "perished" cable section felt in your hands.
If you happen to have two satellite boxes on your system, Look at them. Are they the same model? Same Size? One of those two boxes are powering up that LNA on the dish and one of them sends DC power out of it to the LNA using the coax. So one of those splitters allow DC to pass through the splitter, while the other satellite's splitter connections DON'T.
That's important to NOT swap cable connectors to see if it fixes the problem. But if you have TWO similar models of satellite boxes, you could try swapping the boxes around and see if the satellite starts working normally. That would indicate the power supply in the satelite box is bad and you just isolated it.
Now, under the circumstances that BOTH boxes are the same and you swap them....and you still get that pulsing bar.....that's when you seriously look at the LNA, the splitter(s) or the condition of the cable between the LNA and the splitters.
About the only thing you can really do today is to reconnect the splitter connections about 10 times each and feel the plastic on the cables to determine if weather and sunlight has made the cable brittle. You can swap the boxes if they are the similar model. Don't swap them if they are different.
Got a small TV set? Take it and the satellite box up on the roof with you and you can use them to maximize the satellite's output at the dish. Just a suggestion you can consider..