If you use low-bid coax, the cable co will likely refuse to serve you.
They are responsible to the FCC to keep leakage down to quite low levels. They reuse not just TV spectrum but also aircraft and FM bands. Leakout from their plant gets them unwanted attention...
dSilanskas, What is the proper cable for 1/2 mile? Where will the amplifier be located? What kind of amplifier will be used? How are you going to power the amp?