Clansman (military radio)

For the book by Thomas Dixon, see The Clansman.

Clansman
The PRC 320 HF Radio
Type	Radio Communications System
Place of origin	United Kingdom
Service history
In service	1978 - 2000, 1982 - ~ 2004
Used by	British Army and then Cadet forces
Wars	Falklands War Gulf War
Production history
Designer	SRDE
Manufacturer	Racal, Marconi, MEL and Plessey
Produced	1980's

Clansman is the name of a combat net radio system (CNR) used by the British Army from 1976 to 2010.

Clansman was developed by the Signals Research and Development Establishment (SRDE) in the 1960s, to satisfy a General Staff Requirement (GSR) laid down in 1965. Built by Racal, MEL and Plessey, Clansman represented a considerable advance over existing radios being offered to the Armed Forces at the time. It replaced the aging Larkspur radio system, and proved to be more flexible, reliable and far lighter. The technological advances achieved in the design of Clansman allowed the introduction of Single SideBand (SSB) operation and NarrowBand Frequency Modulation (NBFM) to forward area combat net radio for the first time.

Clansman has been in use by British forces since the late 1970s in most recent UK military operations, the first active use being by 2nd Bn the Parachute Regiment in the Falkland Islands operation in 1982. It is in the process of being replaced by the new digital Bowman communication system.

Family

The Clansman family has been used to refer to the consortium of manufacturers responsible for producing a complete range of military radios for the British Army used in service between 1976 and 2010. In this article The Clansman family of Military Radio Sets, refers to a communications system comprising nine main 2- way radio units, operating in the High Frequency (HF), Very High Frequency (VHF) and the Ultra High Frequency (UHF) Radio Bands. Sets are both vehicle mounted or portable and can be used as ground stations when dismounted.

Models are designated "UK/PRC" or "UK/VRC", which stand for "United Kingdom / Portable Radio Communicator" and "United Kingdom / Vehicle Radio Communicator" respectively. The radios first came into service in the late 1970's and curiously some units of the Army Cadet Force and the Combined Cadet Force were cited as being the first to be issued with PRC349/PRC320 (see below) before some Regular or TA Units. This being due to the age of the equipment they were using at the time, which were obsolete SR88/31/62 sets from the WW2 Era.

At the time it came in service the main advantage of the Clansman radio was that they were all frequency synthesised (switched channels, as opposed to using a variable tuning scale for example). This provided frequency stability, obviating the need to tune the radio again, once a frequency was set. This was a great advantage over previous military radios which were much less stable, and had to be regularly tuned (or might need to be tweaked to "pull in" a weak signal).

Clansman HF Radio Sets

UK/PRC 320

User Handbook AC61123

An obsolete intra-company level HF/USB/AM/CW transceiver built by Plessey. The set operates in the 2-29.9999 MHz range with a possible 280,000 channels. RF power output is a selectable 3 or 30 watts. Derived from an earlier prototype known as the B20, The PRC 320 can be used as a manpack (backpack) (PRC = Portable Radio Communicator) or vehicular radio and it originally replaced the Larkspur Station Radio (SR) A13, SR C13 and other HF Radios in service with the British Army between Ca 1945 and Ca 1978. The 320 can be used with a number of different Clansman antennas supplied with the set for use in varying circumstances; A 2.4m whip antenna is supplied for portable manpack operation using HF groundwave communication. Alternatively a dipole antenna can be used for HF Skywave operation. See VRC 321 below for typical ranges achievable using these modes of propagation. The set can be used as a portable ground station or vehicle mounted, where a vehicle mounted antenna base is used with up to four meters of whip antenna. The UK/RT 320 (the set itself) features a built-in Antenna Tuning Unit (ATU). This electrically matches the whip antenna length to the radio frequency in use. The ATU can also match any other wire antenna, designed or not, for the frequency of operation. This has the effect of making the set versatile and efficient, (leading to anecdotes about the sets capability of transmitting for unusual distances using only improvised antenna, for example a wire fence or a simple dipole draped over bushes). The set is provided with appropriate accessories (or ancillaries) which together make up the complete equipment schedule (CES). This comprises power supply components, batteries, cables etc, audio gear and antenna parts, required to sustain continuous operation alone, for long periods, in a number of configurations. The use of morse code and later data transmission and reception could extend the range and add to the versatility of the UK/PRC 320. See also.

File:PRC 320.png

Notes about HF Antennas. While not intended as a complete description of Clansman Antenna, it should be mentioned in this article, that at High Frequency, wire antennas of either random or tuned lengths are calculated (usually matching a quarter or three quarters of a wavelength for the frequency of operation. These are then fed at one end (hence end-fed) with radio frequency energy (RF) from the ATU or TURF. The RF energy is then radiated away (or propagated)from the antenna system in one or more direction. Various antennas have different characteristics and the type of antenna is usually selected and designed to take advantage of one or more of these. End Fed wires for example are selected to produce ground and skywave radiation and give directionality to the signal, with reduced requirement for height and support, extending the range etc.)

Operational Deployments. One of the first large scale operational deployments of Clansman HF Radios by the British Army took place in December 1979 when the PRC 320 and VRC 321 and others, were deployed by combat signallers of all arms on operation AGILA in Southern Rhodesia - now Zimbabwe. The sets were used to provide a country wide radio net to cover the operations of the British contingent of the Commonwealth Ceasefire Monitoring Force.

Current Users. Clansman HF Sets are still in use in many coutries and by many agencies for example in the UK by the military in the Cadet Forces and also they are quite popular amongst the amateur radio community who can obtain a substantial piece of radio engineering, with history and legend for a few hundred pounds. The radio is easily modified to produce both lower as well as upper sideband and contrary to popular belief, they inter-operate very well with other radios. A good place to hear the radios in use is on the five megahertz band which is shared with the military and used for experimentation with Near Vertical Incidence Skywave and other techniques.

Variants. Several variants of the UK/RT 320 exist. For the British Army the UK/RT 320 was produced with upper sideband only. The 320/L is a version which has lower sideband only, used especially by some Eastern European Forces during and after the cold war. A version known as the UK/RT 320/1 had both upper and lower sidebands and was produced by RACAL. A "tabletop" model was also produced for use by the diplomatic service. A 100 Watt Linear Amplifier and Automatic ATU were also produced to compliment a vehicle mounted radio station.

UK/VRC 321

An obsolete vehicle-borne High Frequency (HF) transmitter/receiver used for inter company communications outside of the normal working range of the VHF forward area nets. The set was also used for rear link communications up to Brigade level and administrative radio nets. In the British Army it provided a useful back up or "guard net", to the VHF radio nets which were prone to jamming by the enemy.

The VRC 321 is a HF Radio which uses USB/AM and\or CW giving an RF output 20 - 30 Watts. the set was Manufactured by MEL, Of Crawley in Sussex and replaced the Larkspur SR C13 and C11 R210 HF Vehicle Stations. These were in service between Ca 1955 and 1978 and used primarily Amplitude Modulation (AM) and Continuous Wave (CW) (Morse). (Although SSB versions of the C11 R210 became available, following the development of SSB). The introduction of Clansman HF Radio therefore saw the adoption of SSB as the standard modulation type for use in the British Army due to its increased efficiency, while AM was provided primarily for interoperability between Larkspur and Clansman Radios after Unit Clansmanisation.

By selecting an appropriate antenna, both groundwave(range up to 40Km) and skywave radiation can be achieved(giving ranges up to 1000Km using Near vertical Incidence Skywave, and beyond 2500Km, using single and multi-hop skywave).

The set is designed to be used in a vehicle (VRC = Vehicle Radio Communicator) using Clansman Harness for example, but the UK/RT 321 (The set itself) can also be used, dismounted from a vehicle, as a ground station with an external power supply or batteries and antenna system. (All clansman radios operate from 24 volt power supplies (with one or two exceptions)).

The set is provided with a CES providing a number of items which together make up the station, for example power cable, antenna tuner unit, coaxial cables and antenna wires etc. Optional accessories such as the selectivity unit radio frequency or SURF were available. The SURF, when tuned, allowed more than one set to be operated from the same position without interfering with each other.

The standard antenna tuning unit used with the UK/RT 321 is the TURF 25 Watts (Tuning Unit Radio Frequency 25 Watts). This could be used either attached to the set, or remotely depending on which antenna configuration was used. Like the UK/RT 320 the 321 is a versatile, simple to operate, HF radio.

(Please See PRC 320 above for a description of the function of an antenna tuning unit or ATU).

UK/VRC 322

A VRC321 station with the addition of a 300 Watt peak envelope power (PEP) linear amplifier (ARF 250W) and appropriate high power antenna tuning unit (TURF 250) manufactured by MEL of Crawley, Sussex.

UK/PRC 319

(Strictly not part of Clansman as developed separately by MEL)

Special Forces and STA Patrol man-portable, patrol level radio HF / VHF, Half-duplex transceiver capable of burst transmission which was built in the United Kingdom by MEL. Features include key-pad entry of frequency, mode and data with digital LCD display; 10 pairs of pre-programmable channels; half-duplex operation with the option of transmitting and receiving on different channels; the option of using a removable pocket sized electronic message unit (EMU) to transmit and receive short data communications; fully automatic antenna tuner which can be remoted up to 50m from the set using standard co-ax cable; Self test facility. power output is 50 watts PEP on high power setting with an adjustable low power of 2-5 watts. Frequency range is 1.5-40 MHz allowing short range VHF communications overlap with the other clansman series radios on the higher frequencies.

Clansman VHF Radio Sets

UK/PRC 349

An intra-section level portable VHF FM transceiver. Built by Racal BCC. RF power output is 0.25 watts. Units supplied to the British Army operate in the 37 - 46.975 MHz range, voice (FM) transmission Mode. A high power (2 Watts) output version was also available and any 10 MHz block in the range 30 - 76 MHz could be supplied. Worn in a holster on the chest or back. The PRC349 was added to the Clansman family in 1972.

UK/PRC 351/352

An intra-platoon level backpack VHF FM transceiver. Built by Racal BCC. The PRC 351 has 4 watt RF power output, and operates in 30-75.975 MHz range with possible 1840 channels. This radio is also capable of being mounted on a vehicle in conjunction with the TUAAM. The PRC 352 is identical, with the addition of a 20 watt RF amplifier and can be used as a ground station.

UK/VRC 353

A vehicle-mounted VHF FM transceiver built by Marconi Space and Defence Systems. The frequency range was the same as the 351/352 with power settings up to 50 W. Antenna systems are provided to provide improved performance in semi-static situations such as an elevated broadband vertical dipole mounted on an 8 metre mast. The VRC is also capable of data transmission and when used in conjunction with an add-on unit (Digital Master Unit)provides a medium level secure speech network.

Clansman UHF Radio Sets

UK/PRC 344

A forward air control UHF AM transceiver. Built by Plessey. Operates in 225-399.9 range with 50 kHz steps for possible 3500 channels. RF power output is rated at 2.5 watts.

Clansman Control Harness and Accessories

Clansman Control Harness refers to a range of accessories which were fitted into vehicles for the purpose of controlling the set(s) and providing other features such as loud speakers, a vehicle intercom system, and switching between two radio sets. Control boxes provided the switching and facilities to plug the audio gear into.

Clansman Audio Gear

A Range of Audio Gear for use in various roles are commonly provided such as; the Lightweight 'B' Vehicle and Infantry Headset (Headset BV and I), the Clansman Handset, a Pressel (Press to Talk or PTT) Switch and the Audio Gear Staff User (AGS). The AGS featured Special Sonovalve technology - a feature designed to allow background noise into the headset through a special valve. In Armoured fighting vehicles an Electronic Automatic Noise Reducing System was provided.

Clansman Accessories

IBRU (Interconnecting Box Radio-rebroadcast Unit)

Used in conjunction with the "Harness" point on VRC 353 and VRC 321 units, to operate 2 or more sets as a Rebro. (ReBroadcast). Re-Broadcasting allows 2+ networks, on different frequencies, to be combined, effectively increasing the ground size of the net. For instance, a vehicle using whip antennas may only be able to communicate 30 km; though placing a Rebro vehicle 30 km away could extend this to 60 km by re-broadcasting the signal on a second net.

DMU

A Digital Master Unit or DMU is used to provide digital communications and to provide secure encrypted communications on a VHF network, when working to similarly equipped radios. This required additional equipment such as the BID 250 and associated Crypto key material.

SURF

A SURF (Selector Unit Radio Frequency) is used to prevent interference to operation of the radio sets. The SURF is an electrical filter, designed to reject unwanted interference from other radios when operating in close proximity to each other. The SURF is tuned using a manual control on the front of the unit, so that only the frequency in use, and those close to it, are accepted by the set. A Range of SURFs were provided for attachment to the VHF PRC350, PRC351/2 (SURF 4 Watt) and also the HF PRC320 (SURF 12 Watt)and VRC 321 (SURF 25 Watt).

Antenna Tuning and Matching

TURF

A TURF (Tuning Unit Radio Frequency) is an Antenna Tuning Unit or ATU. It is used to artificially lengthen the antenna (or tune it) Often at HF wavelengths for example an antenna would be physically too long to attach to a radio without affecting portability and manoeuvrability. A shorter vehicle whip was more practicable and also field antennas were constructed with for example, vertical radiators constructed using the Racal 8 or 12 metre masts. Because these were an electrical compromise, they had to be tuned by use of a TURF (or electrically matched to the set). The TURF 25 Watt (a separate unit to the radio) is considered mandatory when using the VRC321 it tunes both unbalanced, end fed wires and whips and also balanced antenna such as the dipole.

An antenna tuning unit is built into the manpack PRC 320. The TURF requires users to manually tune the antenna, unlike the VHF "TUAAM" which is an Automatic Tuning Unit.

TUAAM

A TUAAM (Tuning Unit Automatic Antenna Matching) is an ATU which matches the antenna at VHF and which is used mainly with the VRC 353 and PRC 351/2 (when used with the clip in kit and mounted in a vehicle). The TUAAM automatically tunes the antenna, and artificially shortens it rather than lengthening it, but essentially it performs the same function as a TURF.

Clansman Antenna

A Range of Antennas specially manufactured for use with Clansman Radio:

Elevated VHF Antenna (EVHF)

An elevated end fed dipole for use with the VHF Radio to extend the range when mounted on an 8 or 12 Meter Mast.

Bob Marley

The late Bob Marley was a Reggae Rock Star, who gave his name to a small UHF Discone antenna in the Clansman family.

Links

http://groups.yahoo.com/group/prc320 http://groups.yahoo.com/group/clansman_larkspur