AM HD Radio DXing a whole new dimension and for those who were concerned AM nighttime HD Radio signals would interfere with existing "clear channel" nighttime reception of the classic analog 50-kW stations, rest easy (yes, there are lawsuits pending over this). It’s all about directionalism with the antenna. Checking this all out recently in Northern Virginia with the Polk iSonic receiver (using the included external AM antenna), it was discovered that if your AM antenna is facing New York, for instance, HD signals from WOR (710) and WABC (770) will interfere with the analog signals of WGN Chicago (720) and WJR Detroit (760)-all as predicted. But if you turn the antenna, the opposite will happen and those analog signals from WGN and WJR will be quite clear. Yes, there is more interference on the dial overall, but it just makes the DXing hobby a bit more challenging. Of course, if you’re driving in the car with no directional antenna capability, that all goes out the window.
Overall, the HD signal interference was less than expected. The only station so far (trying only once and not very late) to come in HD via skywave was WLW-AM Cincinnati. It came in very well and stable. What a difference digital makes! Perhaps it was because 690kHz had only a weak Canadian station airing and the left side HD signal was able to be received, analog interference-free? The switch back-and-forth from HD to analog on WLW was very minimal, but when it did, the broadcast timing was definitely off a few seconds-it does not seamlessly blend as with the FM side.
