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After World War 2 the British Army changed virtually all of their tactical short range radios from HF amplitude modulation to VHF frequency modulation. This step was both operationally and technically of major importance.
This page will highlight the technical side of this drastic modernisation, through illustration of the development of a group of equipment known as the Larkspur range. This equipment, development of which stretched from the late '40s to well int the '50s, has been used extensively by the armies of British and Commonwealth countries and a number of other countries.
Most of the original Larkspur equipment is easily recognised by its well designed light-alloy boxes and Plessey type connectors. The sets are completely sealed and opening a set after thirty-five odd years it invariably shows a virtually brand new interior.
Maintenance is an easy job as the principal Larkspur sets have a main chassis which can be hinged to reveal the sub-chassis, any one of which can be quickly removed. A pre-aligned replacement chassis can be fitted in the field without further need of overall alignment.
In comparison to the operationally similar US AN/GRC 3-8 equipment, the Larkspur equipment uses indirectly heated valves. The circuits of the Larkspur equipment are relatively simple, uncomplicated by the absence of band switching. The difficulty in designing a single set to cover 23 to 60 MHz, which would suit both Royal Armoured Corps and Royal Artillery, forced the designers to produce two models of a similar set which was not uncommon at the time.
The development policy at that time was based on known, reliable techniques, not making use of frequency multipliers or synthesizers, primarily to maintain simplicity and to keep unwanted frequencies to a minimum. The need for frequent calibration was not considered as a major drawback.
Larkspur radios were normally used with a Wireless Control Harness, a system of distribution boxes, junction boxes, amplifiers and connecting cables. The standardisation of the Wireless Control Harness simplified the installation or changes in vehicles considerably.
The design and mechanical arrangements of Larkspur equipment was based on wartime developments with hermetically sealed sets; e.g. Wireless Set Nos. 42, 88 and Reception Set R209.
Station Radio C45 has a frequency coverage of 23-38 MHz in 151 channels with 100 kHz channel-spacing, using an Aerial Tuning Unit No. 9, but is in all respects similar to SR C42. Both C42 and C45 sets were developed as a replacement of Wireless Set No. 19.
Station Radio B47 was developed for communication between tanks and to infantry, equipped with corresponding man-pack equipment. B47 sets replaced Wireless Sets No. 88 AFV and No. 31 AFV. A complete station comprised Transmitter Receiver B47 with internal vibrator power unit and Aerial Tuning Unit No. 8.
Station Radio B47 has a frequency coverage of 38-56 MHz in 181 channels with 100 kHz channel-spacing. The set has continuous tuning with a film scale marked at every channel. Similarly as with the C42/C45, an internal two-stage crystal calibrator and a centre zero tuning meter is used to accurately set each channel. The RF output is 0.5 watt and about 0.01 watt at "low power". The set operates on 24 volts, 12 volt units have been made on a very limited scale.
Station Radio B48 has a frequency coverage of 26-38 MHz in 121 channels with 100 kHz channel-spacing. The Aerial Tuning Unit is a No. 10 model. It is in other respects similar to SR B47. It replaced Wireless Set No. 38 AFV and Wireless Set No. 31B AFV.
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Both C42/C45 and B47/48 use a standard 8 ft vertical rod aerial. To match the 8ft aerial to a set an aerial tuning unit (stores vocabulary TRFA, "Tuner Radio Frequency Aerial") is used. Each set has a different type of tuning unit, depending on the frequency range and the RF power. The aerial tuning unit is mounted in a hermetically sealed die-cast case. This permits mounting e.g. on the vehicle's front wing direct below the aerial base.
C42/C45 and B47/B48 equipment was initially only issued to RA and RAC.
In the late '50s the issue of radio equipment was investigated by the "All Arms Tactical Communications Committee".
Very soon it became apparent that the sets had much value to other arms.
However, no plans had been made for further issue and production had almost stopped.
The committee gauged the possible needs of the entire Army for this radio equipment in a plan named Larkspur, the same as the group of sets. Production was expanded and quite soon the sets ware also issued to other arms including Royal Signals.
In 1962, the year the Larkspur program was launched, a horse named Larkspur running in the Derby races won at 22 to 1. This was considered as a sign for what was bound to be a winning program! Larkspur equipment remained long in production, the manufacture is recorded of C42 No. 3 sets in India up the '70s. 1)
Station Radio A40 is a miniature man-pack VHF-FM transceiver with six pre-set channels in the frequency range of 47-55.4MHz. All sets were equipped with three common frequencies and three other frequencies in an "A" and "B" version, analogue to that used in the No. 88 Set. SR A40 is adapted from the Canadian C/PRC26, having similar specifications and nearly identical mechanical construction. A SR A40 station comprises a hermetically sealed transceiver unit with battery compartment, an antenna and a number of accessories. The RF output is approximately 300 mW. It operates from a combined 90/45/1.5/3 volt dry battery. Station Radio A40 replaced Wireless Set No. 88 and was introduced in the late '50s for use within infantry companies.
|Front panel view of Station Radio A40. Note the slight difference in general layout compared to the C/PRC26. The set is secured to the case by four screws on the sides in place of the clamps fitted on the C/PRC26. The coax socket for connecting a remote antenna is moved slightly to the side and the headgear sockets are level to the front panel, both making access to the function switch more comfortable especially when using gloves.|
|Front panel view of Canadian C/PRC26. All accessories of the C/PRC26 may also be used with Station Radio A40 and visa-versa. Note that with the Canadian parent set the second headgear assembly socket is protected by a spring loaded lid covered with rubber. The dry battery of both sets is the same type.|
|Inside view of C/PRC26 (left) and Station Radio A40 (right). Note that the general construction is quite similar with only very minor production method differences. An important difference is the battery connector. The C/PRC26 has a direct wire connection from the radio chassis to the battery connector on the case. Before removing the case, the battery connector must be loosened. Station Radio A40, however, has an extra connector fitted on the radio chassis which plugs into a the inside of the battery connector.|
Although VHF-FM offered many advantages for speech communication over relative short range, communication over longer distances still depended on HF. HF radios from the same period have been installed and used with the original Larkspur VHF-FM radios.
Station Radio C12 was introduced in the mid-fifties as an interim replacement for Wireless Set No. 19 pending the production of Station Radio C13 for RAC armoured car regiments. It was later reallocated from RAC to a variety of other roles including Infantry when its place in the RAC was taken over by Station Radio C13. Note that this set has many similarities with Wireless Set No. 62 which was produced earlier by the same manufacturer.Table of contents
Station Radio C13 is a medium range HF set, primarily developed for rear communication for vehicular use in forward areas.
It is also used as a ground station.
SR C13 comprises Transmitter Receiver C13, a 12 or 24 volt Power Supply Unit and a Tuner RF Antenna No 11.
The set and power supply dimensions are identical and the front panel layout and tuning up procedure resembles the VHF-FM Station Radio C42 or C45. The equipment provides voice communication using either amplitude modulation or phase modulation, or CW telegraphy up to 20 wpm. The RF output on CW and phase modulation is 20-30 watt, reduced to 10-15 watt with amplitude modulation. The standard power supply operates on 24 volts, a limited number of 12 volt units are manufactured. The set replaced Wireless Set No. 19 (High Power) and Station Radio C12.
Station Radio C11/R210 was developed for medium range HF communication and primarily operated by Royal Signals. A set comprised four units: Transmitter C11, Receiver R210, Power Supply Unit and Tuner RF Antenna No. 7. The set has a frequency coverage of 2-16 MHz in 3 ranges and facilities are provided for amplitude modulation speech, CW Morse and frequency shift keying. The transmitter includes an amplifier for crew inter-communication.
The RF output is 50 watt on high power and 5-10 watt on low power; the Transmitter and Power Supply Units are contained in light alloy boxes and are cooled by fans which draw air through filters on the front panels and expel it through vents in the back of the boxes. These inlets and outlets are provided with sealing covers which, when closed, make the equipment splashproof. Two power supply units are used, a 24 V dc unit and a 100-250 V ac unit. The ac unit also provides the power for the R210 receiver. SR C11/R210 replaced Wireless Set No. 19 High Power and Canadian Wireless Set No. 52.Table of contents
Station Radio A13 is a HF manpack transceiver. Use: Developed primary for infantry use where VHF is unsuitable. It was also employed by amphibious forces and special tasks. Frequency range: 2-8MHz in 2.5kHz channels. RF output 0.8W AM; 1.5W PM and CW. MO with crystal calibrator. AM and PM R/T and CW. Range 5 miles. One man load. Transistorised.
Station Radio A13HP is principally a Station Radio A13 plus an RF amplifier. The employment is similar to SR 13. Frequency range 2-8 MHz. RF output AM 8W; PM and CW 16W. AM and PM R/T and CW. Range 16 miles. Two or three man load. Uses Amplifier RF No. 12.
Station Radio A14 is a manpack HF transceiver. Use: primarily by Royal Marines Commandos and Para Battalions during joint operations. Frequency range 2-8MHz in 2.5kHz interval tuning points. RF output 2W (LP) or 22W (HP). MO or 9 pre-set crystal controlled frequencies. AM/PM R/T and CW. Range 7 miles (LP). One man load. Transistorised.Station Radio A16 (also known as UK/PRC-316) is a lightweight HF Transceiver. Use: Manpack long range patrol set. Frequency range 2-7MHz with 45 channels. RF output 4W. Crystal control. AM R/T and CW. Range several hundred miles. Transistorised.
Station Radio A40 is a short range VHF manpack transceiver. Use: within infantry company but also used in support troops of armoured car and armoured recc. regiments. Frequency range 47-54.4MHz. 6 pre-set crystal controlled channels. Two types (A and B) with three common and three additional frequencies. RF output 0.1 to 0.3W. FM R/T only. Dry batteries powered. Range up to one mile. Operationally interchangeable with C/PRC-26.
Station Radio A41 is a VHF FM manpack transceiver. Use: Within infantry battalion. Frequency range 38 to 55 MHz in 100kHz steps (A41 No. 1) providing 171 channels or in 50kHz steps (A41 No. 2) providing 341 channels. RF output 0.75W. MO control with crystal calibrator. FM R/T. Range 1.5-3 miles.
Station Radio A42 is a VHF FM manpack transceiver. Use: Royal Artillery Observation Post communication to SR C45. Frequency range 26.3 to 38 MHz in 100kHz steps (A42 No. 1) providing 118 channels or in 50kHz steps (A42 No. 2) providing 235 channels. RF output 0.75W. MO control with crystal calibrator. FM R/T. Range 1.5-3 miles. The set has a similar shape as SR A41.
Station Radio A43R is a manpack ground to air UHF transceiver. Frequency range 240-300MHz. 6-pre-set crystal controlled channels. RF output 2W. AM R/T and CW or MCW beacon service. Range depending on altitude aircraft varying from 4 to 100 miles.
Station Radio B43/R220 is a VHF AM static transmitter receiver. Use: Anti-Aircraft Command communications. Frequency range 70-95 MHz in 2 versions. One crystal controlled channel. RF output 12 W. AM R/T only.
Station Radio B44 is a VHF AM man portable transceiver. Use: Communication within light Anti-Aircraft regiment. Frequency range: 60-95MHz. Three crystal controlled channels. RF output 3W. AM R/T only. Range up to 15 miles.
Station Radio B47 is a VHF vehicular transceiver. Use: Primarily for AFV to Infantry liaison. Frequency range 38 to 56MHz in 100kHz steps (181 channels). RF output 0.5W or 10mW (LP). MO control with crystal calibrator. FM R/T. Range 3-5 miles to A41.
Station Radio B48 is a VHF vehicular transceiver. Use: Royal Artillery Observation Posts and Forward Observation Posts communication. Frequency range 26 to 38MHz in 100kHz steps (121 channels). RF output 0.5W or 10mW (LP). MO control with crystal calibrator. FM R/T. Range 3-5 miles to A42.
Station Radio B70 is a light weight man-portable SHF radio relay. Frequency range 4580-4860MHz providing 1+4 channels at 20MHz spacing. RF output 0.3W. Wideband FM for multi-channel operation. Antenna twin 16in dishes. Range up to 60 miles with two relay stations.
Station Radio C11/R210 is a vehicular HF transceiver. Use: Royal Signals operated Division and Territorial Forces command nets and similar roles. Frequency range 2-16MHz. RF output 50W (HP) and 5-10W (LP). MO control with crystal calibrator. AM R/T, CW and FSK. Range R/T 25 miles. Uses separate transmitter (C11), receiver (R210) and supply unit.
Station Radio C11/R210 (ssb) is a vehicular HF transmitter-receiver. Use: similar as C11/R210 with increased range. Particular roles are long distance links in air transported operations, and those where compatibility with existing SSB links is required. Frequency range 2-16MHz. RF output 120W PEP SSB (HP) and 5W PEP SSB (LP), 75W DSB and CW. MO control with tuning in 1kHz steps with calibration. SSB (USB)and DSB with full carrier R/T, CW and FSK. Range R/T SSB 90 miles. Uses separate transmitter (C11 SSB), receiver (R210M) and supply unit. Commercial version Mullard L556.
Station Radio C12 is an interim vehicular HF transceiver. pending the development of SR C13. Use: General purpose HF communication. Frequency range 1.6-10MHz. RF output 5W AM R/T and 8W CW. MO control with two preset channels. Range 15 miles. Interim replacement of WS No. 19. Ultimately replaced by SR C11 and C13.
Station Radio C13 is a vehicular HF transceiver. Use: regimental communication primarily in AFV's. Frequency range 1.5-12MHz. RF output PM and CW 16W, AM 8W (HP) and 1W (LP). MO control with crystal calibrator. AM and PM R/T, CW and FSK. Range R/T 15-20 miles.
Station Radio C13HP is a vehicular HF transceiver. Use: Similar to SR C13 with enhanced range. Frequency range 1.5-12MHz RF output 200W (PM or CW). MO control with crystal calibrator. PM or CW only. Range 45 miles. Uses standard SR C13 and Amplifier RF No. 7.
Station Radio C14 is a medium power HF transceiver. Use: Formation and rear link use in early stages of air transported operations. Frequency range 3-18MHz 8 fixed channels. RF output 100W PEP SSB and 50W CW. Range 50 miles. Commercial (Redifon GR 410) non ruggedised set.
Station Radio C15 is a HF SSB transceiver also known as Collins VC 102. Use: Primarily for airportable roles. Frequency range 2-30MHz. RF output 400W PEP SSB, other modes 100W. 1kHz channel intervals. AM, SSB and DSB R/T, CW and FSK. Range 60 miles mobile SSB. Has autotuning facility and separate Control Unit.
Station Radio C41/R222 is a vehicular radio relay set. Use: In Division and Corps. Frequency range 50-100MHz. RF output 18-35W (HP) and 4-10W (LP). Range 20-30 miles. Wideband FM for multi channel modulation. Can be used for TDM operation (140kB).
Station Radio C42 is a VHF vehicular GP transceiver. Use: Primarily VHF command nets (including Corps, Division, Territorial Forces and Units) and AFV's. Frequency range 36-60MHz in 100kHz steps (Nos. 1 and 3) providing 241 channels or in 50kHz steps (No. 2) providing 481 channels. RF output 15-20W (HP) or 0.5W (LP). MO with crystal calibrator. FM R/T. Range 10-15 miles.
Station Radio C42HP is a VHF high power transceiver. Use: General purpose for command communications within Division. Frequency range and modulation as C42. RF output up to 1kW. Range 30 miles. Comprises SR C42 and Amplifier RF No. 10.
Station Radio C45 is a VHF vehicular GP transceiver. Use: Primarily VHF command nets (including Corps, Division, Territorial Forces and Units) and AFV's. Frequency range 23-38MHz in 100kHz steps (Nos. 1 and 3) providing 151 channels or in 50kHz steps (No. 2) providing 301 channels. RF output 15-20W (HP) or 0.5W (LP). MO with crystal calibrator. FM R/T. Range 10-15 miles.
Station Radio C45HP is a VHF high power transceiver. Use: General purpose for Artillery communications from Corps to Division. Frequency range and modulation as C45. RF output up to 1kW. Range 30 miles. Comprises SR C45 and Amplifier RF No. 10.
Station Radio C50 comprising Transmitter Radio C50 and Receiver Radio R236 is a mobile radio relay. Use: Forward areas Division and Brigade level. Frequency range 225-400MHz for TDM and FDM operation. RF output 10/50/250W. The station superseded Station Radio C41/R222.Station Radio C70 is a mobile radio relay. Use: In Division and Corps areas. Frequency range 610-960MHz for FDM and TDM operation. RF output 10W. Range about 25 miles. Set is a modified version of the Siemens FM 12/800 system.
Station Radio D11/R234 is a vehicle mounted medium power station. Use: Down to Division or Brigade. Frequency range 2-22MHz. RF output 100W DSB (AM R/T), 300W CW and 350W SSB. Range (mobile) 60 miles.
Station Radio D13/R234 is principally a high powered version of the D11 and contained in the same cabinet. Use: long range communications. Frequency range 2-20MHz. RF output 250W DSB, 700W CW, 900W SSB. Dual diversity reception and RTTY operation.
Transmitter Radio E10 is a high power static transmitter. It was principally used in Army Chain stations (COMCAN). Frequency range 3-25.6MHz. RF output 30kW SSB, 6kW AM R/T and 20kW CW. Worldwide range. Previously known as WS No. 15. Commercial Marconi set.
Station Radio BCC HF 156 is an interim HF manpack transceiver pending the development of SR A13. Use: Developed primary for infantry use where VHF is unsuitable. See here the front panel of this set. It was also employed by amphibious forces and special tasks. Frequency range: 2.5-7.5MHz. Receiver MO. Transmitter 6 preset crystal controlled channels. RF output 1W AM R/T and 2W CW. Range 3-5 miles. Commercial set adapted for Army use. Photo's courtesy Keith Watt RGN MRCN (G4MSF)
Station Radio CPRC-26 is a short range VHF manpack transceiver. Use: within infantry company but also used in support troops of armoured car and armoured recc. regiments. Frequency range 47-54.4MHz. 6 pre-set crystal controlled channels. Two types (A and B) with three common and three additional frequencies. RF output 0.1 to 0.3W. FM R/T only. Dry batteries powered. Range up to one mile. Operationally interchangeable with SR A40.
Station Radio A510 is a HF manpack transceiver. Use: Jungle set for Infantry Company patrols where VHF would be unsuitable. Frequency range 2-10MHz. Four pre set channels for transmitter. Receiver MO. RF output 0.3W. AM R/T and CW. Dry batteries powered. Range 3-5 miles. Production in Australia and adopted in limited numbers by British Army.
Station Radio BCC 46U is an interim VHF manpack transceiver. Use: ASSU ground/air communications with close support aircraft. Replaced by Station Radio A43R.
Beacon Set, Radio MR 343 is a lightweight transponder beacon. Use: Dropping zone marker beacon. Frequency range 200-240 MHz (Eureka/Rebecca equipment).Table of contents
|TRFA (or ATU)||used with|
|No. 5||SR C12|
|No. 6||SR C42|
|No. 7||SR C11/R210|
|No. 8||SR B47|
|No. 9||SR C45|
|No. 10||SR B48|
|No. 11||SR C13|
|No. 12||SR R210 (receiver only)|
|No. 13||SR A13|
|SR C14||SR C14|
|No. 15||SR A14|
Used in multi-set vehicle installations to reduce mutual interference.
|Rejector Unit||used with|
|No. 3||SR B47/B48/C42/C45|
Amplifiers Radio Frequency
|Ampl RF||used with|
|No. 7||SR C13HP|
|No. 9||SR C11|
|No. 10||SR C42/C45|
|No. 12||SR A13HP|
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|A||0-10 watts||Dry battery operated||Manpack|
|B||10-100 watts||Low Power sec. batteries||Man portable|
|C||100-1000 watts||Medium Power sets||Vehicle|
|D||1kW-10kW||High Power sets||Transportable/Mobile|
|E||Over 10kW||Very High Power||Transportable/Fixed|
Frequency range indicated by figures:
|10-39||300 KHz - 30 MHz||(MF-HF band)|
|40-69||30 MHz - 3 GHz||(VHF-SHF)|
|70-99||Above 3 GHz||(SHF-EHF)|
With the introduction of the Clansman range of equipment in the 1970s a more sophisticated joint system of equipment nomenclature was issued, quite similar to the current USA system.
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