Thats interesting Rod. Back in the day when A.M. was the main reception medium a lot of effort was put into making the sound as good as possible. Nowadays, the a.m. band is just included for convenience (if its included at all) and the sonic performance is usually pretty dire. The problem with using the off-tuning method to hear the higher audio frequencies is the A.G.C. This will generally try to over compensate for what it sees as a reduction in signal strength and distortion starts to creep in because the receiver cannot de-modulate cleanly. A variable BW IF is a great solution, but who is going to bother to design that in these days. Some of the world receivers have BW settings for IF but i dont think they generally are as wide as 18khz are they ?