I am not 100% familiar with US915 but each mask enables eight (8) 125kHz channels and one (1) 500kHz channel.
E.g. Mask 0001 enables 125kHz channels 0 - 7 and the 500kHz channel 64.
right, so that the at+mask doc is wrong means that the ‘max’ channels isn’t supported? that’s fine but was why i started looking at the at+mask command (i didn’t make this explicit).