You probably need a directional antenna because you are likely dealing with multipath. I suggest that you go to Radio Shack and buy their FM only outdoor antenna for $20. Their computer designed yagi is an exellent unit, and don't let the snobs tell you differently. Nothing else you can buy for under $100 even comes close. Bring it home, and hold it in your hand and see if you can get a good clean signal. Compare it to your rabbit ears and/or any little powered unit (Terk et al). If you problem is not solved, take the darn thing back to Radio Shack and they will refund your money. If it turns out that you do need the outdoor antenna, you can put it in your attic or use it as a decoration in your son's bedroom.
Cheers,
Sam
Cheers,
Sam