You can buy an non-powered amplifier at radio shack for ten bucks. They sell plug in models that are more powerful.
Directv booster or amplifier
Anyone have any experience with these? I've got close to 90 ft of cable from my dish to a splitter and then another 30 ft to my receiver to my Pioneer Elite. Got a great pic but sometimes I get some posterization or shadowing. I'm wondering if I need a booster to boost the signal, any help will be greatly appreciated.