RG-8X is just a slight bit better than RG-58 at most scanner frequencies and for any real lengths should be avoided. RG-8U is generally a better bet than 58 or 8X for scanner frequencies. Not great, but not bad. That said, you need to get quality coax and not cheap junk. If you can't confirm that what you're getting is good quality, assume it's junk and pass it by. Also if buying it used you need to confirm that it was stored properly since it can be quickly ruined by water either from direct contact or high humidity.