The Canopy 5.4GHz 30/60 Mb BH variant uses a 12MHz

The Canopy 5.4GHz 30/60 Mb BH variant uses a 12MHz channel raster, whereas the 5.7GHz 30/60 variant uses a 6MHz raster. Why is this?

To allow flexibility within the 125MHz of spectrum available at 5.7GHz 30/60 Mb BH system was designed with a 6MHz channel raster giving 19 channels. In order to keep the Canopy 5.4GHz 30/60 Mb BH 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. At 5.4GHz there is 255MHz of available spectrum. To cover this 255MHz of spectrum the 5.4GHz channel raster is set to 12MHz.