Plessey Avionics           PTR3411     " Groundsat" 


I' m told (on extremely good authority)  that approximately 100 of these were sold and in 1980 they  were selling for  about 5000 pounds sterling ! They have not been manufactured for about 20 years , unfortunately the Plessey Avionics company no longer exists in its original form and  has been gobbled up a long time ago and the remanents may be under the large German  electronics Siemens group.???  If you have  or know the where abouts of any of these  "groundsat"  units please let me know        I have a fascination for them! 

Below is a collection of information that was kindly sent to me By Chris Richardson , also a UK radio Amateur , G3NAE
 whose "baby"  it actually is,  his name appears on the American patent No. 4134068  ( and on various other comms patents) for this radio communications technique , He is  still doing advanced research work on this concept , ( and others!) 

Visit our website at

Roke Manor Research Ltd, Roke Manor, Romsey, Hampshire SO51 0ZN, UK.

The concept is hard to swallow when you first read of it however think of it this way , There are a lot of 10 Ghz /24 Ghz WBFM transceivers about that are able to run Full Duplex communication ,( talk and listen AT THE SAME TIME)   They usually use an Intermediate Frequency of 30 Mhz , For duplex comms to work, you must transmit with an offset of 30 Mhz between both stations at 10 Ghz./24 GHz ( so far so good ! ??)  ok so we change our IF to 10.7 Mhz , full duplex concept still works and the concept is perfectly understandable ??  ok  lets change our IF to 100 Khz   concept still understandable ??  10 Ghz/24 Ghz  oscillators are now 100 Khz apart  to get the 100 Khz IF ..     OK now l suggest we change our IF to dc or  "ZERO IF "  ( baseband , ie audio frequency 300-3KHz,  IF as in a direct conversion SSB receiver)  they work ok dont they ?? Now you can see how we can still achieve  full duplex communications  ( transmitting and receiving ,CONTEMPORANEOUSLY !)  on the same frequency!  There are some constraints to this and they are to do with the intercept point of the receiver mixer, L.O   phase noise etc and methods to minimise the deleterious effects of these on the quality of the received signal at  microvolt level , .after my "simplistic" explanation ,  are you now convinced that this is possible!. 


Groundsat is a compact VHF (FM) Manpack Transceiver offering unique facilities.  Designed primarily to improve the communications capability of existing v.h.f. combat -net radios, it is an omni-directional, common-channel rebroadcast station with the ability to receive and transmit simultaneously on the same frequency.  It gives the user far greater chance of making radio contact by dramatically increasing the coverage in problem communication areas. This previously unobtainable facility greatly improves the operational use of a network as well as reducing the frequency planning problems associated with con­ventional rebroadcast operations.

^Single Frequency Tactical Manpack Repeater/Rebroadcast Station

•^Operates on the same frequency as your radio network

•^Dramatically increases the chances of 'getting through*

•^Unattended operation

•Eases frequency allocations

•^Full military specification and frequency range (30-76MHz)



    Groundsat deployed for action !


General "

Common channel rebroadcast

Duplex operation

Simplex operation

Additional facilities


Frequency planning

Operator convenience



Communications limited by difficult terrain Enhanced performance achieved by Groundsat


2.1     GENERAL

The Plessey Groundsat* System is based on the PTR 3411 VHF Transceiver,  This is a compact, manpack v.h.f. (f.m.) transceiver covering the military frequency range from 30 to 76MHz in 25kHz channel increments.  The system embodies a revolutionary new concept in communications technology, permitting simultaneous transmission and reception on a common radio channel. As a result, the *Groundsat1 system is perhaps the most versatile ever offered in the military tactical radio communication field.  The following modes of operation are available;                  |

(a)  Common channel rebroadcast

(b)  Common channel duplex

(c)  Simplex           |

These are described in the following sections.


By virtue of its unique ability to receive and transmit simultaneously on the same radio channel, the system is capable of rebroadcasting received narrow-band frequency-modulated signals without channel translation, giving a signal power enhancement in excess of lOOdB (lO117 times), In this mode, the system is designed for unattended op­eration, remaining in its 'Standby* condition until required for use by a subscriber.  The subscriber transmits a command signal which activates the rebroadcast transmitter.  The rebroadcast station then transmits an acknowledgement tone to the initiating subscriber to indicate that it is operational and ready for use.  The station remains operative for a nominal period of 45 seconds.  The end of this rebroadcasting period is signalled by the transmission of a 'time-out* tone, after which the re­broadcast station reverts to its 'Standby* condition. The rebroadcasting period may be extended at anytime by transmission of a further command signal - it is not necessary to wait until 'time-out* has occurred. Facilities are provided to permit local monitoring of radio traffic through the rebroadcast station and to permit a local operator at the station to 'break in' on such traffic

An audio tone is heard in the receiver earpiece if both transmitter and receiver are in an operational state. The test may be performed in radio silence if the antennas are not connected.  Alternatively, it may be used in con­junction with the deployed antennas to provide the operator with a subjective means of selecting the optimum re-broadcast transmitter power for use in a particular situation. if desired.  Additionally, a local operator may initiate   transmission from the rebroadcast station, giving him a half-duplex control capability over simplex net sub­scribers.  When used in this manner, the controller can provide 'talk-through* facilities between net subscribers on demand.


This mode of operation permits two PTR 3411 'Groundsat' stations to interoperate to provide a full duplex radio circuit for analogue speech signals, using the same radio channel for transmission and reception.  In order to avoid operational problems which might arise from the continuous radiation of a radio carrier even when the link is idle, the standard equipment configuration provides 'press-to-talk* transmitter operation in this mode,


In this mode, the PTR 3411 'Groundsat* equipment operates as a conventional, narrow-band f.m. simplex manpack, with a maximum power output of nominally one watt.  A Clansman-compatible tone squelch system  (150 HZ )is used.  The antenna is a 1.5m broadband whip.


Two test facilities are available at the equipment front panel.  These are described below.


This test mode is provided to assist in the deployment of the antennas in the 'rebroadcast' or 'duplex* modes.  These t;wo modes of operation utilise separate transmitting and receiving antennas and whilst their deployment is by no means critical, the 'test overload* facility is provided to indicate to the operator the minimum antenna separation necessary for optimum performance of the system.  The test mode provides a continuous tone in the handset earpiece if the antennas are sufficiently separated for optimum oper­ation,  The tone ceases if the antennas are too close to­gether.


This test permits the operator to perform a rapid and com­prehensive 'loop-round* check on the operational state of the transceiver.  Operation of the handset pressel switch in this test condition modulates the transmitter with an audio tone and switches on a calibrated r.f. test signal.


The  'Groundsat' System offers significant advantages over conventional rebroadcasting systems. These stem from its unique capability of rebroadcasting without the need for channel translation, from the wide range of facilities offered and also from its ease of transportation and deployment.  The advantages of the system are examined in  more detail in the following sections.


Combat net radio transceivers in current use employ single frequency simplex operation.  In view of the varied nature of operating terrain, it is often not possible for net sub­scribers to maintain direct radio contact.  This has led to a requirement for radio repeater stations, for which a typical current deployment is shown in Figure 3.1.  Here it is seen  that when subscribers cannot communicate directly, they are compelled to route messages via the repeater station to a third party on another frequency for onward transmission. Frequency separation requirements in excess of 10% are not uncommon, and further constraints on the actual frequencies to be used are often imposed by equipment design limitations  arising from such causes as spurious receiver responses, spurious transmitter outputs and the various problems en­countered  in operating transmitters and receivers simultan­eously in close proximity.

The 'Groundsat* system using the same radio channel for re­ception and rebroadcasting, avoids all these problems.(Figure 3.2).  It is capable of operation on any 25kHz in­cremental channel between 30 and 76MHz simply by selecting the desired operating frequency.  When deployed, its use is optional to subscribers;  if they are able to intercommuni­cate  directly, they may do so, using the 'Groundsat' facility only when it becomes necessary as a result of terrain or distance limitations on direct communication.   


The advantages offered by the 'Groundsat' system in this respect may be considered in two categories. The first of these concerns the actual rebroadcast station. In a conventional system, , it is  necessary to 'cross-couple* two separate transceivers, using the receiver from one in conjunction with the transmitter  from the other, to achieve a satisfactory rebroadcast configuration.  This leads to increased bulk, often requiring a vehicle for transportation which limits the choice of rebroadcast sites to those having vehicle access.  The need for a vehicle, often at a hilltop site, also poses   problems of concealment. In contrast with this situation, the complete 'Groundsat station may be transported by one man to sites inaccessible to  vehicles;  it may be deployed very rapidly, checked for satisfactory operation and left unattended if desired.  Re­deployment to accommodate changing tactical situations is fast and simple.  As an additional advantage, the built-in 'simplex* operating mode permits an operator to maintain normal radio contact with his net while  in transit to the  selected rebroadcast site.

The second aspect of operator convenience is seen when considering the requirements of subscribers to the rebroad­cast  net.  The battlefield environment places severe re­strictions on radio equipment with regard to size, weight and operator  convenience.  In general, this leads to a re­latively simple, single frequency simplex transceiver specification for  combat net radios.  In order to employ such an equipment in a conventional frequency translating rebroad­cast system, it would be necessary for outstations to switch manually between two frequencies when transmitting and receiving, precluding the possibility of direct communication between subscribers.  This severe disadvantage is sufficient to prevent the general application of automatic rebroadcast techniques in combat nets. The 'Groundsat' system permits the general use of rebroadcasting techniques in simplex nets, placing no additional demands  on the operator;  the rebroadcast station is brought into operation by means of a small unit connected into the operator's  microphone lead.  Double operation of his pressel switch initiates a 45 second rebroadcast period. The enhancement in area coverage provided by the 'Groundsat' system permits net coverage to be maintained using smaller, lower powered transceivers than those previously required.


The improvement which may be expected in net coverage when using the 'Groundsat* system is illustrated in  Figures 3,3 and 3.4.  Figure 3.3 shows the locations of 60 actual test sites in hilly terrain, generally within a 5km radius, from which it was attempted to establish two-way communication



With a headquarters station located in a valley as shown. Map grid squares represent 1km.  Standard proprietary  combat net radios were used, equipped with standard blade-type battle antennas.  The shaded rectangles represent those sites at which "successful two-way contact was es­tablished with the headquarters station: i.e. 9 only out-Of a possible 60. The 'Groundsat' system was then deployed on high ground overlooking the headquarters location and the entire test was repeated.  The results are shown in Figure 3.4 in which shaded rectangles again show those locations 'at which two-way contact was successful.  This time contact was made with 49 out of the 60 sites:  a dramatic improvement directly attributable to Groundsat.  A reprint from Defence magazine for October 1978 detailing these tests is included at the back of this document. (not on this site )


Some of the advantages concerning ease of deployment of the 'Groundsat' system have already received mention 'in the preceding sections.  The complete station may be transported without difficulty by one man, giving the widest possible  choice of location.  On route to the chosen site, the operator is able to use the 'Groundsat' transceiver as a conventional manpack providing simplex communication to the radio net.  On arrival at the site, the two ground-mounted antennas are  rapidly erected, requiring a typical but not critical separation of some 20m (standard 5m masts may be used if desired for  further enhancement of performance).  The antenna feeder cables are connected to the transceiver and the desired operating  channel is selected by means of four front panel controls.  The equipment is then switched to the 'rebroadcast' mode and is ready for use.  If desired, a very simple and rapid 'loop-round' check on the operation of the equipment may be performed to provide a comprehensive check on the operational state of the transceiver. A further test facility is provided for use in locations where space for antenna deployment is limited;  the faci­lity is available from the equipment front panel, and in­dicates to the operator when the antennas are too close together for optimum rebroadcast performance.    



The PTR 3411 'Groundsat1 transceiver (Figure 4.1) comprises a v.h.f. (f.m) manpack transceiver, housed in a sealed and  dessicated case of aluminium alloy.  Detachable top and bottom cover plates provide access to the internal circuits. Provision is made for a range of proprietary rechargeable batteries to be attached to one side of the case by means of quick-release fasteners.  The other side face of the case contains a bayonet socket which accepts a 1.5m broad­band whip  antenna for simplex operation.  A standard re­placeable dessicator cell is screwed into the rear face of the case  which also carries a socket for connection of an external power supply for trickle charging the battery. The equipment front panel contains the following controls and connectors:

(i)   Transmitter antenna connector -

50 ohm BNC

(ii)  Transmitter volume control switch 
(iii) Transmitter power control switch 
(iv)  Operating mode switch with the

following positions:



(v)   Four frequency setting switches with the following functions:  
(a)  10MHz steps  
(b)  1MHz steps  
(c)  0.1MHz steps  
(d)  0.025MHz steps 
(vi)  Audio connector - 7 pin Clansman Pattern 105 
(vii) Receiver antenna connector - 50ohm BNC

Internally, the case is divided horizontally by a central screening partition;  the lower section created by this partition  is subdivided by three vertical partitions.  This form of construction provides exceptionally good access ^' for maintenance purposes,                             


The electrical circuits are contained on seven double-sided printed circuit boards, each board having components mounted  on one side only.  All components are clearly identified by means of white silk-screened legends. All printed circuit boards are secured by means of slotted . screws, and all board interconnections are by means of plug  a-nd socket connections.  Extensive use has been made of ribbon-type cables and flexible printed wiring to minimise the complexity of internal wiring.  All switches are mech­anically integral with their associated printed circuit boards, their  control shafts being mechanically coupled to control knob and sealed spindle assemblies.  By this means, all printed circuit boards may be removed without unsolder­ing operations, leaving sealed spindle and bush assemblies in the front panel permanently undisturbed.


Electrically, the equipment consists of the following assemblies:

(i)   Transmitter

(ii)  Synthesiser

(iii) Voltage-controlled Oscillator

(iv)  Receiver                ;

(v)   Transceiver Control Board

These are described in the following sections.


The transmitter module consists of the following printed circuit syb-assemblies:

(a)   Transmitter board assembly

(b)   Transmitter filter board assembly

The purpose of the module is to amplify and filter signals . in the frequency band 30 to 76MHz.  The transmitter circuit is  designed for broadband operation over this range.  The filter assembly rejects harmonics of the transmitter output frequency;   it covers the operating band by means of two switched low-pass filters contained on a single board assembly.  Filter  switching is effected by means of change­over relays, which are operated by a control signal derived from the  frequency-setting switches.  Switching from one filter band to the other ,occurs at a frequency of 49.975MHz.


The output of the transmitter is maintained at a constant level over the operating band by means of a gain-controlled , loop in which the amplitude of the output is compared with a preset reference voltage.  This provides a high degree of .  amplitude stability and also serves to minimise amplitude-modulated noise products at the transmitter output. RF amplification is obtained in three transistor stages, broadband matched over the operating range  hiQ coaxial  connectors* Advanced circuit design and component tolerancing techniques have been used to eliminate the necessity for adjustable components in any r.f. circuit of this module.  The entire setting-up of the unit may be accomplished by means of a single preset variable resistor. The transmitter output circuit is fully protected against open or short-circuit load conditions.


The prime frequency source for transmitter drive and receiver " local oscillator signals is provided by a digital frequency synthesiser.  This consists of two separate board assemblies, containing a wide-range voltage-controlled oscillator (v.c.o)  and digital synthesiser control circuits respectively.  These are contained in individual screened compartments. The v.c.o. assembly consists of a varactor-diode-controlled variable-frequency oscillator, two wideband buffer amplifiers  and a synthesiser control loop filter.  One of the buffer amplifiers provides the final r.f. output of the synthesiser, whilst the other drives the frequency synthesiser control circuits located on the synthesiser board. The v.c.o, circuit is capable of being frequency-modulated by audio signals applied to its varactor diodes. The synthesiser control circuit board accepts the buffered v.c.o. output, which is applied to a chain of fixed and variable  divider circuits.  The division ratio is selected by means of four frequency-setting switches which form an integral part  of the board assembly.  The output of the variable divider circuits is applied to a phase and fre­quency comparator circuit, in which it is compared with a reference signal derived from a high-stability crystal oscillator,  The output from the comparator is used to con­trol the frequency of the v.c.o.  A second output from the comparator is used to drive a light-emitting diode which is situated on the board to provide an 'out-of-lock* indication for maintenance purposes. The synthesiser control board assembly also contains the necessary circuits to apply frequency modulating signals to the  v.c.o.  In a rebroadcast system intended for use with tone-squelch controlled transceivers it is important to pre­serve  the integrity of the rebroadcast squelch tone deviation.  This is achieved by the use of a patented control circuit which  maintains the frequency deviation at a con­stant level for a given modulating signal over the entire operating frequency range of the synthesiser. The high stability reference crystal on the board is also used to derive, by means of fixed divider stages, a  Clansman-compatible 150Hz squelch tone for transmission when the transceiver is used in the 'simplex* mode.


The purpose of the receiver is to receive and demodulate narrow-band frequency modulated signals in the frequency range  30 to 76MHz.  It consists of two associated sub-units; an r.f. filter assembly and a receiver assembly. The incoming signal is applied to the r.f. filter assembly, which provides bandpass filtering over the operating band in two ranges.  Range switching occurs at a frequency of 49.975MHz.  Switching is achieved by means of changeover relays which  are driven by a control signal derived from the synthesiser frequency-setting switches.  The assembly also provides filtering for the local oscillator signal, The receiver is a direct conversion unit based on Weaver design with a Zero IF. The filtering signal is split into two separate components, each of which is applied to a mixer. Thus quadrature IF at base-band is generated , The filtered and  amplified mixer output signals are up-converted to a second intermediate frequency and combined together.  The combined up-converted signal is demodulated in a pulse-counting discriminator and amplified before passing to the transceiver control board for further processing.  Automatic gain con­trol is provided. The receiver also contains the circuits necessary for suppressing the unwanted signals which originate from its companion  transmitter operating at the same nominal carrier frequency. Two test functions associated with the transceiver are contained in the receiver.  The first of these is a comb generator which generates frequencies at 1MHz intervals of the radio frequency band covered by the transceiver.  The generator is operated by a control signal derived from the  transceiver control board.  The comb of frequencies is ap plied to the receiver input as a test signal. The second test function consists of an r.f. sensor contained on the receiver filter board.  Its purpose is to detect excessive r.f. signal levels appearing at the receiver input from the associated transmitter antenna.  The sensor output is amplified and taken to the transceiver control board, where it is used to generate an audible test tone in the receiver earpiece.


This assembly contains all the necessary control, timing and switching functions to permit the transceiver to be operated in the 'simplex', 'duplex* and 'rebroadcast' configurations.  It also permits selection of the two built-in test modes;  these are 'test transceiver' and 'test over­load',  In addition, the control board contains detectors for demodulation of received squelch tones and rebroadcast command signals, the modulation VOGAD circuit and receiver headset amplifier.  A description of the various modes of operation is given in the following sections.

(i)    Simplex Operation  . In this mode the microphone input signal is routed through a VOGAD integrated circuit which is 'enabled* by the microphone  pressel switch.  The VOGAD.output is combined with a 150Hz squelch tone and this combined signal is used to modulate the transmitter.  The pressel switch also controls transmit/receive switching of the transceiver. On the receive side, the audio input to the control board from the receiver is taken- to a squelch tone detector and gate, through an audio shaping filter, speech expanding amplifier and volume control to the handset amplifier.  The microphone  output is also taken to the handset amplifier to provide an audio side-tone facility,

(ii)   Duplex Operation

When this mode is selected, the transmission and reception audio paths are the same as for . 'simplex' operation, with the exception that   the receiver squelch gate is disabled, so that the receiver is not muted.

(iii)  Rebroadcast Operation

• When the transceiver is switched into this mode, the receiver output is taken to the detector which demodulates the command tone which enables automatic rebroadcast operation.  Reception of this tone causes a logic signal to be generated which routes the receiver output through a frequency-shaping network and amplifier to the transmitter modulation input.  In addition, the transmitter and an associated interference-cancelling circuit are switched on for a timed period of approximately 45 seconds. Reception of a rebroadcast command tone also switches on a 1kHz oscillator and applies this,  together with a 'squelch* tone, to the transmission modulation input for a period of some 1.5 seconds.  This permits the transceiver to broadcast a confidence signal to the originator indicating that the rebroadcast station is ready for  use.  At the end of the 45 second timed period, these tones are again broadcast for a short period to notify users that the rebroadcast facility is about to terminate.  It should be noted that the re-broadcasting interval will be prolonged if a further * command tone is received during the 45 second 'on* period. While the transceiver is rebroadcasting, the receiver output is applied through the closed squelch gate to the handset  amplifier for local monitoring periods.  Operation of the local microphone pressel switch in this condition disconnects the audio rebroadcast loop to permit a local transmission to be made When the station is in its idle condition, operation of the local microphone pressel switch twice in rapid succession  initiates all the functions normally controlled by the output of the rebroadcast command tone detector, with the exceptions  of the transmission of a 1kHz con­fidence signal and associated squelch tone.


(iv)   Test T/R Operation

This test position provides a transceiver 'loop-round* test.  In this mode a 1kHz tone is generated for use as a test modulating signal for the transmitter and logic signal enables an r.f, comb generator on the receiver board to serve as a test input signal to the receiver.  Operation of the microphone pressel switch permits a squelch tone to be transmitted in  order to test the receiver.

(v)    Test 0/L Operation

In this mode, the transmitter is switched on by means of the microphone pressel switch. A detector in the receiver antenna circuit provides a logic signal which controls the state of the 1kHz oscillator on the control board.  The output from' the  oscillator is routed to the handset amplifier to provide an audible indication when the received signal from the transmitter  is below a pre­determined level. (vi)   Additional Functions (a)  Whenever the equipment is switched on, a pulse derived from the battery supply is generated on the control board to  condition all relays in the transceiver to their correct initial states.

(b)  RF band selection The control board also contains a trigger circuit which accepts a logic signal from the frequency setting switches on the synthesiser.  The output of the trigger op­erates relay drivers which control the state of r.f. filter-switching relays located on the transmitter and receiver filter assemblies.



Frequency range: 30 - 76MHz

Channel spacing: 25kHz or 50kHz  

Number of channels: 1840 or 920

Frequency stability; better than 15 p.p.m.

Modulation: FM voice 5kHz deviation & 150Hz tone squelch (1.6kHz or 3.2kHz deviation)  

Modes of operation:

1) common channel rebroadcast for simplex nets

2) simplex transceiver

3) common channel duplex transceiver

  Test modes:

1) test overload (antenna separation)

2) loop-round (overall equipment test)

  Rebroadcast ratio greater than lOOdB

Power supplies: 24V nominal rechargeable battery pack

Battery life: nominally 12 hours with PV 1304 battery

  Dimensions (without battery): 95mm 275mm 250inm  

height .width depth

Weight: -5.5kg approx  

Operating temperature range: 20°C to +65°C



generally meets the requirements of DEF STAN 07.55



Power output: nominally high nominally 1W in 50Q,100mW in50Q,nominally lOmW in 50Q

Carrier deviation: ±5kHz

Modulation sensitivity; ImV to 40mV for full deviation with automatic level control

typically 1uVfor lOdB SINAD ratio Sensitivity:

Audio output: ,1V r.m.s. into 75Q (adjustable by volume control

Audio bandwidth: 3dB bandwidth 300Hz to 3kHz

Squelch: 150Hz tone squelch •none



rebroadcast received squelch tone is re­transmitted



5                      ANCILLARIES 5.1     CALL OSCILLATOR

This is a small audio tone generator unit which is connected in the user's microphone lead.  It is required by each user of  the net in order to 'call up* the Groundsat rebroadcast facility as described in Section 4.2.4 (iii). It takes the form of a small 'black box* (size approx 89mm x 38mm x 29mm) fitted with a Clansman 7 pin socket on the input (microphone) end and terminated at the other end in a Clansman 7 pin plug on a flying lead.

5.2     ANTENNAS 


The normal antenna used with the radio in its simplex man-pack role is a 1.5m whip antenna, which plugs directly in­to the top of the equipment.  It consists of five inter­locking sections of metal tube, with a nylon cord running down the middle which permits the antenna to be broken down for storage and prevents the sections from becoming mislaid.  Reassembly is accomplished by pulling on the cord, and then winding the slack round a ferrule at the base of the antenna.  A spring-loaded angle.adaptor allows the antenna to be deployed in any position.


For use as a rebroadcast station two PV 3415 centre-fed antennas are recommended.  Each antenna consists of a ground spike which carries a wideband antenna matching unit.  The antenna, which takes the form of a fibre-glass whip, plugs into the top of the matching unit and is connected to Groundsat by means of an r.f. feeder cable.  Where conditions demand it, the range of Groundsat may be considerably enhanced by mounting the PV 3415 antennas on 5.4m masts.

The Company manufactures several other v.h.f. antennas, suitable for use with Groundsat in its manpack and re­broadcast roles.  Details of these will be found in the brochure "Tactical VHF Antennas" at the end of this document.


5.3.1  GENERAL

Groundsat is designed fco operated from 24V rechargeable alkaline batteries.  The battery may be trickle-charged, while  the transceiver is operational, by the use of a d.c. powered charging unit (Section below) or a mains p.s.u. (Section 5.3.4 below).


The rechargeable batteries use the Plessey-patented tem­perature differential charging system.  Temperature sen­sors are fitted in matched pairs, one inside each sealed nickel-cadmium cell and one outside, and the battery char­ger compares the inside and outside temperatures contin­uously.  When the battery is fully charged, the excess en­ergy from the cell is given  off in the form of heat, and this rise in internal temperature terminates the charge. Using this method, charging times are greatly reduced, a higher battery capacity is obtained, and maximum use of the charging equipment is ensured. Standard Batteries PV 1302 & PV 1304

These batteries are housed in strong black plastic cases. Two thumbscrews retained in the battery by spring clips, secure the battery to the bottom of the transceiver.

The PV 1302 has a nominal capacity of l.SAh which gives the transmitter-receiver an operational duration of approxi­mately 7 hours when operating on a 1:2 (transmit:standby) ratio.

The PV 1304 has a nominal capacity of 4Ah giving an oper­ational duration of approximately 12 hours at a similar operating cycle, Clansman Batteries

An adaptor plate is available which permits the PTR 3411 to be powered from the Clansman lAh and 3.3Ah batteries, or the hand generator.

The batteries are sealed rechargeable units housed in riv­eted and welded aluminium cases, and use the temperature-differential charging system as described in Section 5,3.1. Approximate charging time is 4 hours for the 3.3Ah bat­tery. Clansman Hand Generator

The hand generator system is designed to operate the transmitter-receiver unit in emergencies and in the patrol role.  The battery is clipped to the bottom of the generator and the top of the generator is attached to the transmitter-receiver by means of the battery adaptor plate.  The generator and the battery together can provide sufficient power to the main unit to permit indefinite operation.

The generator is turned by hand and a light, complete with shroud, is provided to indicate when the handle is being turned at the right speed.  The output of the hand gener­ator is 330mA at 28V.  -    -

The weight of the hand generator, complete with lAh battery, is 3,6kg.

5.3.3   BATTERY CHARGERS PV 2328A AC Charging Unit        .  ,

The PV 2328A operates from 95-125V or 190-250V a.c., 45 to 60Hz, and provides two groups of six output channels.  The charging current can be set by a front panel control for each group of channels, approximate limits being 50mA, 100mA, 200mA and 350mA.  Since the charger is current lim­ited, any battery with a terminal voltage of 6-28V may be charged.  The 200mA setting is normally used for PV 1302, and the 350mA setting for PV 1304 and Clansman 3.3Ah bat­teries,

The unit is protected against output short-circuit, and will withstand transportation in an unpressurised aircraft up to an altitude of 7,500m.  It is fully sealed against ingress of dirt or moisture, and is undamaged by immersion in water to a depth of 1 metre for 2 hours duration.  The charger has an operating temperature range of -40 C to +55°C, and may be stored in temperatures up to +75 C:  its dimensions are 140mm x 275mm x 250mm, and its weight is 8kg.

5.4 PV 2328B AC Charging Unit                   -  .

The PV 2328B operates from 95-125V or 190-250V a.c. , 45 to 60Hz, and provides six trickle charge outputs and one ra­pid charge output.  The charging current may be limited to 50mA, 100mA, 200mA or 350mA on the trickle charging outputs, and is preset to 2A maximum on the rapid-charge channel, Rapid charging is terminated by the temperature-differential method, and this facility must only be used with the stan­dard batteries PV 1302 and PV 1304, and the lAh and 3.3Ah Clansman batteries. The environmental and mechanical parameters of the unit are the same as for the PV 2328A described above.

ft - Clansman AC Charging Unit

The alternating current charging unit (a.c.c.u) is capable of charging up to 16 mixed-capacity batteries simultaneously, using the temperature-differential charging system.  It is powered from a 100 to' 120V or 200 to 250V a.c. supply of 45 to 66Hz. Each charging circuit is provided with an amber and a green indicator lamp.  The amber lamp is on when the charge is proceeding:  it is extinguished and the green lamp lights when the charge is complete. The worst-case charge time for a PV 1304 battery is four hours, The unit is mounted in an RAE type case and weighs approxi­mately 29.5kg (65 Ib) including the cables. DC Charging Unit

The Clansman direct current charging unit (d.c.c.u) can be supplied for operation from either 12V or 24V supplies. It is a fully sealed unit designed for use in the most ard­uous military environment, and carries lamps to show when the charge is proceeding and when it is finished.  The unit will charge any of the batteries in-situ:  charging times vary from 1^ hours for the Clansman lAh to 4 hours for the PV 1304.

  The power source for the d.c.c.u, may be any external d.c. source of adequate power with a nominal voltage of 12V or 24V as appropriate, such as a vehicle battery supply, sig­nal battery or d.c. generator.


The PV 2325 operates from 110/220V a.c., 45-65Hz, and pro­vides a nominal 28V d.c. regulated output suitable for powering equipments which consume up to 12A average current.  Its peak output is 15A. Designed for use with tactical radio equipment under battle conditions, the PV 2325 will operate in the presence of a strong electromagnetic field without interference, and may be used with h.f. or v.h.f. transmitters or transceivers. When used as a trickle charger for Groundsat, a 10ohm  resistor must be included in series with the output to limit the charging current. The unit is housed in a finned casting with a detachable top cover, which is sealed by an 'O* ring.  A desiccator socket is included, and the unit may be immersed in water to a depth of 1 metre for two hours or more without suffering any damage.  A current limiting circuit comes into operation between 15 and 18A to prevent damage from overload, and a temperature sensor interrupts the mains input to prevent heat damage. The dimensions of the unit are 145mm x 275mm x 245tnni, and its weight is 12kg.


The audio gear is lightweight and of modern design.  It has • been designed to meet the rigorous and varied environmental conditions experienced in all roles of combat usage.


The headset is of double earphone type with a standard in­sert of 300Q impedance.  The earphones are connected in parallel to give a nominal impedance of 150ohms The boom microphone is carried on the same frame as the head" set.  The standard 300Q impedance insert has a sloping frequency response to accentuate the high frequencies and thus improve speech clarity. A six-way lead with a separate pressel box connects the headset to the radio.  A two-pole sprung switch on the pressel box controls both pressel line and microphone and is used to activate the call oscillator to put the Ground-sat in the rebroadcast mode,    



The lightweight handset is fitted with the same earphone and noise-cancelling microphone insert as the headset. The lead is also the same, but the pressel switch is integral with the handset grip.



The carrying satchel is designed to be worn on the back, and accommodates the transceiver with a battery attached, a spare battery, the 1.5m whip antenna and the audio gear. Flaps in the satchel can be opened to allow access to the front panel controls and to the connections for the anten­na and audio gear, so that the radio may be used in the manpack role without the normal carrying frame.


The carrying frame provides a comfortable means of carrying the unit on a man's back while allowing him maximum freedom of movement and minimum interference with his standard army packs, webbing and personal weapons.  The frame is equipped with polyurethane-impregnated nylon straps that are adjustable for comfort and have a quick-­release toggle.




Transmitter-receiver PTR 3411 Battery secondary, PV 1302

Clansman Handset, general purpose (5965-99-620-5669)

Carrying frame

Antenna mount assembly .

Antenna, whip 1.5m

PV 3415 Centre-fed Antenna

Cable, r.f. 20ra (5995-99-620-5803)

User handbook

Part No. (^o(^?t|45^6

630/1/42630 605/1/00573 640/1/15062



686/9/01389 686/1/01500 686/1/00504/002


Call Oscillator (Clansman interface) 612/1/41660


Carrying satchel                     630/9/37599/001

Call oscillator (special) (specify interface)

To be advised ^{i A-ltet




Batteries, Chargers, etc. Battery'secondary, l.SAh, PV 1302 Battery secondary, 4Ah, PV 1304

Clansman battery, secondary 24V 3.3Ah  


Part No.




605/1/00566 640/1/14605

630/1/38988 503/1/02050


Plate, interface, battery PV 2328A Battery Charger 12 way

PV 2328B Battery Charger  6 way + 1 rapid

PV 2325 Mains PSU DC Charging Unit

Hand Generator System Plate, interface, battery

Generator, electrical hand



Battery secondary, 24V lAh (6140-99-620-8058)


Rack, electrical equipment ('clip-in* kit)

PV 1317 Mounting Tray





640/1/15063 640/1/15064

Audio Gear

Clansman Handset, general purpose (5965-99-620-5669)

Clansman Headset microphone ,



Cable assembly, switch electrical




VHF Antennas

Mast kit, 5.4m (5820-99-621-9027) -


See also brochure at back of document Tactical VHF Antennas



The major functions which determine the maintainability philosophy which has been adopted for the equipment are the operational requirements, conditions of use and reliability.  The influence exerted by these considerations on the maintainability policy are examined in the follow­ing sections.

(i)    Operational Requirements

The unique versatility of the PTR 3411 Transceiver renders it suitable for use in a wide range of applications which may be classified into three groups, defined by the three oper­ational modes provided by the equipment.

(a)  Rebroadcast- operation

In this application the equipment may be deployed unprotected and unattended for periods of up to 12 hours with a standard battery, on a standby-to-transmit ratio of 2:1.  Alternatively, the equipment may be deployed statically in a suitably equipped vehicle, in which case a vehicle-derived power supply might be used for attended operation over ex­tended periods.  In current British mili­tary practice, operational periods of up to seven days might be required in such a deployment.

(b)  Duplex operation

In this mode of operation, circumstances in which the equipment is both unattended and unprotected are not generally envisaged. The requirement for an operator implies a requirement for some degree of environmental protection, particularly if protracted per­iods of deployment are envisaged.  The oper­ational duration can be taken to be generally similar to that specified for rebroadcast operation.


(c)  Simplex operation

This is a conventional single-frequency simplex manpack application, in which the equipment must operate in a re­latively harsh mechanical environment, with minimal protection.  It may be expected to be used often at its maxi­mum transmitter power setting, in which case its operational duration will be some 20 hours on a receive-to-transmit ratio of 10:1.

(ii)  Reliability

The predicted mean time between failures (m.t.b.f.) for the transceiver is 800 hours, using Military Handbook 217B, Method 2.

(iii) Environmental Categories

The equipment has been designed for operation in the following environmental categories as defined in DEF STAN 00-1/Issue 1.

Al.  Hot Dry

A2.  Intermediate Hot Dry

Bl.  Wet Warm

B2.  Wet Hot

B3.  Humid Hot Coastal Desert

Cl.  Intermediate Cold


The equipment is housed in .a sealed and dessicated case;

opening of the case for any reason in an adverse environ­ment would be detrimental to reliability.  For this reason, no provision is made for first line servicing.  However, the equipment has been provided with a loop-round test facility to permit the operator to perform an immediate check on its functional state. In order to maximise the availability of the equipment, the main emphasis in the maintenance philosophy has been placed on second line servicing.  At this level, simple diagnostic routines, using the built-in test points, provide rapid  


location of a faulty printed-circuit module and servicing at this level is performed on a module exchange basis.

Faulty modules identified at second line level, or com­plete equipments not repairable at second line, are refer­red to third line servicing.  At this level, fault diagnosis to component level is carried out.  For this purpose, each module is provided with a number of test points for use in conjunction with test jigs and routines described in the maintenance handbook for the equipment,


Second Line Servicing

For ease of fault location and repair at second line level, the equipment has been designed in such a way that each major circuit function is contained on a separate printed circuit board. Each board is secured in the equipment by means of slotted screws;  all interconnections between boards and front panel controls are by means of plugs and sockets.  No special tools or solder­ing operations are required for removal and re­placement of any board, and sealed control spindles are not disturbed.  The use of test points in conjunction with the maintenance handbook provides rapid identification of a faulty board.  Pre-aligned printed circuit boards are provided as factory spares for second line use, thus permitting direct replacement by relatively unskilled person­nel without further adjustment.

Third Line Servicing

Servicing at 3rd line, or base workshop level can be carried out with standard proprietary test gear without the need for special jigs and fixtures. However where the throughput is such as to justify its use, a. range of test jigs, into which boards may be inserted for fault location and alignment, can be supplied.  In order to minimise the capital cost of third line maintenance, such jigs, whenever possible, make use of proprietary test equipment which may be already available to the user.  Each board is furnished with test points to permit checks to be made on circuit conditions, signal levels and logic states in conjunction with data contained in the equipment maintenance handbook.  All integrated circuit modules containing more than eight connecting leads are mounted 'in high-reliability plug-in     sockets to facilitate replacement.    

  A special Thank you to Chris Richardson, G3NAE  of  Roke Manor Research Ltd   U.K    for this information  ( it was he whose name appears on  the patent for this amazing radio !! )  

and to Joe Bell  G4PMY  of    BELL RADIO SYSTEMS ,,, avid collector of all things in  military  communications ..    see website  who gave me the opportunity to own this radio,  I hope he enjoys the RACAL 4021 I  back pack HF  radio  traded !!  ( it cost us both an absolute fortune in airmail postage between NZ and UK !! )

Yes,  I have all the circuitry  for this amazing device !( thanks Chris)        


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