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[1] 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.
Despite being developed for re-equipping the post-war British army, the first delivery of Larkspur equipment went to Nigeria.