A lot of the HD receivers out there, with exception of a few of the newer ones such the Insignia portable and the Sangean rack tuner, are unbelievably deaf. They are awful analog tuners and even worse HD receivers. The Boston Acoustic one that I have is within 2-4 miles of most of the Clear Channel transmitters and unless you monkey around with the antenna, you don't get many of them in analog with any regularity, let alone HD. The other stations, inlcuding Class C's 15-20 miles away? Forget it.
It's a well documented problem. Moreover, receiver penetration is squat.