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LARKSPUR

by Louis Meulstee PA0PCR


See the  "Larkspur Image Directory" first!

Note that the background colour of this page is slightly different to the rest of my site, matching the colour of the Larkspur range of equipment.

Table of contents of this page

Introduction
VHF FM
Hermetically sealed
Two basic models
Station Radio C42/C45
Station Radio B47/B48
Aerial Tuning Unit
Larkspur
Manpack sets
Station Radio A41-A42
HF radios
Station Radio C13
Station Radio C11/R210
Wireless Control Harness
RF Amplifiers
Abridged technical details of Larkspur equipment
Additional Larkspur equipment
Post War British equipment nomenclature
Finally
References and acknowledgements


INTRODUCTION

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 the early '50s, has been used extensively by the armies of British and Commonwealth countries and a number of other countries.

Most of the 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 are 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 simplifies the installation or changes in vehicles considerably.

R-209  26kb

Reception Set R-209

Larkspur equipment is based on wartime developments with hermetically sealed sets; e.g. Wireless Set Nos. 42, 88, 38 Mk.3 and Reception Set R-209 (shown in picture).


In 1961 the contraction WS (Wireless Set, - Station or - Sender), as a general indication for a complete radio station which is capable of being operated, was superseded by SR (Station Radio). In this web site page this notation has been used except for those sets which were considered as obsolete, but still in limited use at that time.(e.g. Wireless Set No. 88).
The term "Transmitter-Receiver" (contraction TR) is used for a transceiver or transmitter-receiver unit. It may include the power supply when this is an integral part.

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VHF FM

In the early stages of World War 2 the advantages of VHF-FM, applied to tactical radio communication, were apparent. However, it was not practical to make such a far reaching change in the British army.
The US Signal Corps, not directly involved in the war until 1942, and thus being in a much better position, were able to change most of their tactical short range radios to VHF-FM. After World War 2 the USA SCR-300 VHF-FM set (BC-1000) was adopted by the British as Wireless Set No. 31, complemented by Wireless Set No. 88. Both sets, the first British tactical VHF-FM radio's, were introduced about 1948.

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HERMETICALLY SEALED

Between 1955 and 1957 the radio equipment of all tanks and armoured vehicles of the Royal Armoured Corps (RAC) and Royal Artillery (RA) was exchanged for a new generation of sets, operating on VHF-FM. Both arms were allocated a frequency band ranging from 23-69 MHz, very similar to the signal designation in the US Army.

- The RAC (but later also Infantry, Royal Signals and other arms) operated in the "high" end of the band ranging from 36 to 60 MHz.
- The RA operated in the "low" end of the band ranging from 23 to 38 MHz, allowing an overlap of 2 MHz.

The design and mechanical arrangements of the sets were based on war-time developments of hermetically sealed equipment such as Wireless Sets No. 42, No. 88, No. 38 Mk.3 and Reception Set R209.

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TWO BASIC MODELS

The new generation of radio equipment consisted initially of two basic models: firstly an "A" set, Station Radio C42 or C45, with a range of about 10 miles, comparable with the "A" set of the 19 set. Secondly a short range "B" set, Station Radio B47 or B48, comparable with the 19 "B" set, primarily intended for inter-tank communication and supporting arms. The versions of each model differed only in frequency range.  Later many other sets were added to the original Larkspur models, sometimes not very consequently and thought merely in connection with the nomenclature of that period.

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STATION RADIO C42-C45

Station Radio C42 was developed for radio communication in tanks and other vehicles. The station comprises transceiver TR C42, (incorporating a crew intercom amplifier), a power supply unit and an Aerial Tuning Unit No. 6. The frequency coverage is from 36 to 60 MHz in 241 channels with 100 kHz channel-spacing. A version developed later, SR C42 No. 2, is suitable for 50 kHz channel spacing. The set has continuous tuning with a 12 ft film scale marked at every channel. An internal two-stage crystal calibrator and a centre zero tuning meter enable each channel to be set accurately. The RF power output is 15-20 watts, reduced to about 0.5 watt in 'low-power' position. The standard vibrator power supply unit is powered from 12 or 24 volts, the 24 volt unit being in more general use. Later manufactured units use a transistor inverter.

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.

C45  41kb

Transmitter-Receiver C45.

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STATION RADIO B47-B48

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.

B47  45kb

Transmitter Receiver B47.

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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AERIAL TUNING UNIT

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.

Tuner RF Aerial No. 6  48kb

Tuner Radio Frequency Aerial No. 6 as used with Station Radio C42

Tuner RF Aerial No. 6  50kb

Inside view of Tuning Unit No. 6

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LARKSPUR

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)

C45 in Rover  78kb

Station Radio C42 fitted in a Landrover.
Note that the set is powered from a separate pair of batteries allowing the station to be removed from the vehicle and used as a ground station. Aerial Tuning Unit No. 6 is fitted on the left hand front wing, just below the aerial base.

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MAN-PACK SETS

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.

  

British Station Radio A40     Canadian C/PRC-26

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.

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STATION RADIO A41-A42

SR A41 was developed for radio communication with infantry and liaison to B47 sets in supporting armoured vehicles. It was introduced in the late '50s and replaced Wireless Set No. 31. The frequency coverage is 38-55 MHz in 171 channels with 100 kHz spacing. The RF output is approximately 0.75 watt. The set has continuous tuning with a filmscale marked at every channel. The scale is calibrated to separately marked check points by a single stage oscillator which is tuned for zero beat in the headphones. In the early '60s a No. 2 version was introduced with 50 kHz channels, to work with C42 No. 2 sets. Similar to Station Radio A41 is the SR A42, having a frequency coverage of 26-38 MHz in 121 channels with 100 kHz channel spacing. The set was introduced for communication for FOA (forward artillery observation) parties, working to SR B48, replacing Wireless Sets No. 38 and 31B.
SR A41 is developed from the US AN/PRC 10 (RT-176). The A42 set, having a different frequency coverage to the A41, is developed from the US AN/PRC 9 (RT-175).

A41 39kb

Station Radio A41

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HF RADIO'S

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.

C12  54kb

Station Radio C12

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.

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STATION RADIO C13

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.

C13  41kb

Transmitter Receiver C13 with 24 volt Supply Unit No. 16.

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SR C11/R210

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.

C11/R210  42kb

Typical installation of Station Radio C11/R210.

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.

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WIRELESS CONTROL HARNESS

The Wireless Control Harness is a versatile system of control units, junction boxes, amplifiers and connecting cables, designed for the installation of the Larkspur range radio equipment in virtually any vehicle. It provides the control of several radios from various positions in a vehicle including inter-communication facilities. Although primarily designed for vehicles, it is used in installations which have been dismounted and set up in ground stations. Two versions of the Wireless Control Harness are used:
- Type "A", mainly for use in tanks with two or three-set radio installations.
- Type "B", for use in other vehicles using only one or two radio sets.

A number of standard units, each having its specific application connected by standard cables, are used to make a particular harness, meeting the required type of installation.

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RF AMPLIFIERS

In the Larkspur range a number of RF amplifiers were developed increasing the range of a standard set. An RF amplifier is driven by the RF output of a standard set.
- Amplifier RF No. 7 is used in conjunction with a SR C13 forming SR C13 High Power. The RF output power at CW or phase modulation is 200 watts.
- Amplifier RF No. 9 is an universal RF amplifier, used with Station Radio C11/R210 delivering a RF output of 1kW CW or 400 watts amplitude modulation.
- Amplifier RF No.10 provides a RF output power of 1 kW in the frequency range 23-60 MHz, applicable to SR C42 and C45.

Amplifier RF No. 7  41kb

Amplifier RF No. 7

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ABRIDGED TECHNICAL DETAILS OF LARKSPUR EQUIPMENT


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.

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 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 14 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/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, 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.

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. 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.

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 a 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).

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ADDITIONAL LARKSPUR EQUIPMENT



Tuner Radio Frequency Antenna

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

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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POST-WAR BRITISH EQUIPMENT NOMENCLATURE

The British nomenclature for wireless sets, dating back to 1929, was maintained until 1948. By then it had proved that it had many limitations and incorrect designations.
In the post-war system a revised nomenclature system was devised not having the drawbacks of the previous system. A set is given a letter followed by two figures. (e.g. A40, B47, C11) The letter indicates the total power input to the complete radio station. The figure indicate the part of the frequency spectrum in which the set operates and also gives the chronological order of the set.

Total power input of a station indicated by a letter:

Power input Type Function
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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FINALLY

The introduction of the Larkspur range radios can be regarded as a major step forward in comparison with the previous world-war 2 equipment. It was not just the use of VHF-FM, but also the thoroughly designed equipment and the versatile control harness which made the Larkspur range of equipment a long lasting success.

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ACKNOWLEDGEMENTS

The author wishes to thank Deputy Director and Staff of the Royal Signals Museum, Blandford Camp, Dorset, UK, for permission to publish various illustrations and for their help in preparing the original article. The article on which this page is based, has been published previously in Q-Five, The Old Timer's Bulletin and Radio Bygones.

REFERENCES

1) The Vital Link, P.Warner, 1989, Cooper, London, isbn 0-85052-8828
2) Radio in Mobile Warfare, Publication No. 768, Jun 1955.
3) United Kingdom Combat Area Radio Equipment, SRDE, Oct 1961.
4) Telecommunications Equipment Technical Summaries, SRDE, May 1959.
5) User Handbook for Wireless Control Harness Type 'B", Feb 1956.
6) The Royal Signals Reference Manual, Pt 4, Equipment data, Apr 1962.
7) "Larkspur", L.Meulstee, Q-Five, Vol. 2, No. 1, February 1993, pp9-16.
8) "Larkspur", L.Meulstee, The Old Timer's Bulletin, Vol. 34, Nov. 1993, pp35-40
9) "Larkspur", L.Meulstee, Radio Bygones, No. 35, June/July 1995, pp20-26.

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Larkspur diagram  46kb

Diagram depicting the application of Larkspur series radio's.

The Larkspur program involved not only a large scale introduction of C42-45 and B47-48 vehicular VHF-FM sets to other arms, but also the introduction of other new equipment such as VHF-FM infantry man-pack sets and HF radios. An example of the tactical deployment of VHF-FM radios is shown in this diagram; in addition to the model numbers, a basic technical summary of each set is provided. Royal Artillery, (left); Infantry, (centre); Royal Armoured Corps, (right).


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