To cover the whole band using Canopy 5.4GHz 30/60 Mb BH,

To cover the whole band using Canopy 5.4GHz 30/60 Mb BH, I have to change the channel raster. Why is this?

In order to keep the Canopy 5.4GHz and 5.7GHz 30/60 Mb BH operation and user interface as similar as possible, the number of channels that the system can tune to has been kept the same at 19. It is not possible to cover the 255MHz of spectrum available with 19 channels spaced at 6MHz centers, hence the need to change the channel raster to 12MHz.