There are several things you can try to improve the picture quality of your cable on a 4K TV. First, make sure that your TV is properly calibrated. This means adjusting the picture settings to get the best possible image. You may need to experiment with different settings to find the ones that work best for you.
Another thing you can try is adjusting the resolution of your cable box. If your cable box is set to a lower resolution, it may cause the picture to look poor on your 4K TV. You can usually adjust the resolution of your cable box in the settings menu. If you are not sure how to do this, you may want to consult the user manual or contact your cable provider for assistance.
In addition to these steps, you may also want to consider upgrading your cable package to get access to higher resolution channels. Many cable providers offer packages that include 4K channels, which can provide a much better picture than standard HD channels.
Finally, it is worth noting that some older content may not look as good on a 4K TV as newer content. This is because older content was often filmed or produced at lower resolutions, and it may not be possible to upscale it to 4K without sacrificing some picture quality. If you are experiencing this issue, you may want to consider purchasing a 4K Blu-ray player or streaming device to access higher quality content.