New head unit, same problem.

Hey guys, ever since i bought my mustang, about 3 years ago, i have had a radio delivery issue. It would cut out randomly or when i come to a stop it would be all static unless i moved an inch forward.. I assumed it was just a faulty HU since my 00 and 01 are both running the same 12/13 in antenna and neither of them are having the same issues as my 02. Everything works fine when it goes into HD mode until it starts to lose signal and it just moves back and forth from SD to HD. It just gets on my nerves when it does that since to make the change it either over laps or cut off the sound. Is there any way the cable could be causing this or am i just getting interference from some outside force? Thanks for any information you all have.