prior to september 1935 a raster of channel allocations based upon multiples of 5 khz progressively developed, but with the complex lattice of allocations implemented, the effective raster was 15 khz. with the massive expansion of national and commercial services planned for the 1930s, the old raster would not have permitted satisfactory co-existence of the desired services. in the years prior to 1935, the regulator developed a plan based upon 10 khz channel spacing, essentially identical to that which had been in use in north and south america (itu region 2).