I have the biggest OUTSIDE antenna walmart sells, and yes, I also have an 18 db booster. I haven't talked to ANYBODY with a converter box that has been happy. With the new tv we get great reception on most channels, but still don't get some channels we used to get with analogue. This is going to have to do. POWDERMAN.

Is it specifically a UHF antenna? A lot of the antennas (both indoor and outdoor) were designed for the VHF spectrum which is what most of the old channels were on. All digital stations now transmit over UHF. An antenna designed for VHF signals will still pick them up, but not nearly as well as one specifically designed to receive UHF frequencies (if you look at most old rabbit ears for example you usually have the rabbit ears and then a circular loop - the ears are for VHF and the loop is for UHF,and on many of them you'll notice those huge rabbit ears with a tiny UHF loop thrown on as an after thought

).
It could also be in your distance too. Digital is an all or nothing deal - it comes in perfect or it comes it choppy (or not all all). If you were on the edge of the broadcast area you might have gotten a staticy but watchable analog picture before, but the digital transmission won't likely have enough bits make it through to render the image.
PS Also, make sure with your amplifier that you have it as close to the antenna as you can, rather than the TV. Amplifiers really help with longer cable runs (particularly from outside), and so it helps to amplify the signal at the beginning of the run. If you stick it at the end of a long cable run much of the signal has degraded and you're just amplifying a signal that's already gotten noisy.