Maybe you need a new pre-amp, and maybe you don't. It's a good idea to make sure the rest of the antenna system is working well beforehand. A new pre-amp can't help you if it's not getting decent signals in the first place. That means:
1. Looking for physical damage to the antenna, or excess foliage and/or tree debris lying on it. Lower the antenna, brush off any debris, and gently bend any crooked elements back into shape by hand. Pay close attention to the phasing lines, those cross-crossing metal wires running above the boom. These carry signals to the downlead, and they can't do the job if they're touching each other or the boom
anywhere (or there's a big, damp oak leaf, pine needles, etc. lying across them). Finally, is the antenna badly darkened from corrosion, or are several elements broken off completely? It may be time to consider replacing the antenna.
2. Inspecting the downlead for cracks in the insulation, or corrosion on or inside the connectors, particularly outdoors. This presumes you're using coaxial cable right now. If you note any signs of aging or rust, or there's flat twin lead anywhere in the system, consider replacing all of it now with RG-6 coaxial cable. Thankfully, coax is cheap. Good thing, seeing as how it can be a pain to pull new wiring! If you replace the cabling, replace the $5 coax matching transformer that connects the coax to the antenna as well. They wear out over time, too.
3. Replacing the pre-amp if the fixes above don't make much of a difference in your reception. RS amps tend to be very noisy, and noise is the enemy of good
DTV reception. Lots of posters cite the CM 7777 because it has notably brawny gain figures, but the real reason it works so well is that it's probably the quietest consumer-grade pre-amp available. Or not: Thanks to the transition, it's been back-ordered by most places for an average of two weeks. If you want a pre-amp right away, a good alternative is the Winegard HDP-269, which is now carried by local RS stores. If only a CM 7777 will do, go ahead and get it. It's suitable for your signal environment.