Based upon the discussion above regarding the very wide deviation of the FM carrier in most of these devices, it is possible that these devices could become a significant problem with digital HD Radio receivers. Since the IBOC signals are occupying “vacant” adjacent channels, it is likely that these are the exact channels a user would choose upon which to operate one of these devices. To the user, the “noise” like HD Radio carrier appears to be a vacant channel. However, with the wide modulation capability and the strong signal levels emitted by these devices, it is likely that significant interference to the much lower power HD Radio signals would be caused. The spectrum plots in Figs. 10 and 11 shows an HD Radio carrier with the Part 15 device off and on, respectively.
Figure 10
Part 15 Device OFF – HD radio carrier can be seen in the “vacant” channel
