Well, I can think of only three other possibilities: either your signal is being blocked somehow, the cable is broken somewhere between the antenna and the outlet, or your amplifier (booster) is busted. A little troubleshooting with a DVM may be in order.
Gary Shapiro, 2011 Georgetown 29' Class A
Dash, Molly & Lily - now at the Bridge and forever in my heart
Shadow - 4-year-old Greyhound
Hannah - 1 1/2-year-old GSD rescue