Larkspur radio system Larkspur was the name of a tactical radio system used by the British Army . Its development started in the late 1940s with the first equipments being issued in the mid - 1950s . It remained in service until replaced by Clansman in the late - 1970s although some elements of Larkspur were still in service into the 1980s . It was widely exported to British Commonwealth armies and other friendly nations . The origin of Larkspur was a post - war project to move tactical short - range radio communications in the forward battle area from HF using amplitude modulation to low - band VHF using frequency modulation . 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 . The range of sets originally comprised the vehicle VHF sets C42 , C45 , B45 , B47 , B48 , the A13 HF manpack transceiver 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 known as the " New Range " to differentiate them from wartime legacy radios . They were characterized by similar tuning drills , frequency indication using film strip displays , the use of relatively simple architecture that avoided complex switching as far as possible and using commonly available components and a degree of modularity in construction . An important operational advance was that the sets incorporated internal calibration facilities which meant that they could be accurately pre - set on a frequency without radiating any signal . This enabled all stations on a net to be confidently pre - tuned on the same channel and dispensed with the old compromising " Tuning and Netting Call " system that advertised the presence of a net to an enemy . All the sets were constructed in strong hermetically sealed alloy enclosures - a measure that had been found to be essential to ensure durability and reliability during the previous war . Initially , roll - out of the VHF New Range sets was restricted to the Royal Armoured Corps and the Royal Artillery , however a project to re - equip the rest of the army was undertaken and given the name Larkspur , the name becoming retrospectively applied to the original New Range sets and eventually by common use becoming a generic title for virtually any radio equipment used by the British Army between the end of WWII and the arrival of Clansman . VHF manpack sets of the era were derived from established designs with the Station Radio A41 and A42 being developed from the US AN / PRC 10 and 9 respectively and the A40 adapted from the Canadian C / PRC - 26 . Other sets developed commercially were bought in to suit specialist needs , examples being the HF156 , A14 ( BCC30 ) and Redifon A43R . The A13 HF manpack set was notable for being the only set in the original range that employed transistors and a rechargeable nickel - cadmium battery . Various other sets such as the B70 UHF carrier telephony relay , C11 / R210 HF transmitter / receiver for Royal Signals use , and the transmitter D11 and its associated receiver , the R230 were commercial developments adopted by the British services . Trivia . Despite being developed for re - equipping the post - war British army , the first delivery of Larkspur equipment went to Nigeria .