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Your odds of a successful and reliable attic installation are near zero even if you execute a plan perfectly, there simply isn't much signal available at this location and the attic location will likely make the signals too weak to be usable. If you cannot reconsider that choice, you may wish to stay with alternatives unless you're willing to expend what might end up being considerable effort and expense for what is an uncertain outcome.

A one story ranch with 8' ceilings with a 5/12 roof will usually give an attic that is between 10' and 20' above the ground. Actual height will depend on the size of the ranch, height of the walls, the pitch of the roof, and whether the ground is relatively flat or if it's sloped.