 This followed the similar move by the US Army in the latter part of WWII which had demonstrated significant advantages.Where the use of VHF was not practical, HF sets using narrow band phase modulation (NBPhM) were developed as the only practical method at the time of obtaining some performance improvement over the use of AM especially at night.The range of sets originally comprised the vehicle VHF sets C42, C45, B45, B47, B48 and the C13 vehicle HF transceiver, all of which were designed to specifications produced by the government Signals Research and Development Establishment (SRDE) at Christchurch and initially designated as the "New Range" to differentiate them from wartime legacy radios.