Although there was interest in the new FM band by station owners, construction restrictions that went into place during WWII limited the growth of the new service. Following the end of WWII, the FCC moved to standardize its frequency allocations. One area of concern was the effects of tropospheric and Sporadic E propagation, which at times reflected station signals over great distances, causing mutual interference. A particularly controversial proposal, spearheaded by RCA, was that the FM band needed to be shifted to higher frequencies to avoid this problem. This reassignment was fiercely opposed as unneeded by Armstrong, but he lost. The FCC made its decision final on June 27, 1945. It allocated 100 FM channels from 88–108 MHz, and assigned the former FM band to 'non government fixed and mobile' (42–44 MHz), and television channel 1 (44–50 MHz), now sidestepping the interference concerns. A period of allowing existing FM stations to broadcast on both low and high bands ended at midnight on January 8, 1949, at which time any low band transmitters were shut down, making obsolete 395,000 receivers that had already been purchased by the public for the original band. Although converters allowing low band FM sets to receive high band were manufactured, they ultimately proved to be complicated to install, and often as (or more) expensive than buying a new high band set outright.