Radio Frequency Hazards To JSP 482 Edition 4 Electro-Explosive Devices CHAPTER 24 RADIO FREQUENCY HAZARDS TO ELECTRO-EXPLOSIVE DEVICES

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Radio Frequency Hazards To JSP 482 Edition 4 Electro-Explosive Devices

CHAPTER 24

RADIO FREQUENCY HAZARDS TO ELECTRO-EXPLOSIVE DEVICES

CONTENTS Para

1 RADIO FREQUENCY HAZARDS TO EEDs 1.1 Introduction

1.2 Statutory Requirements

2 SUSCEPTIBILITY

2.1 Factors Affecting Susceptibility

2.2 EED Testing for Susceptibility to EM Radiation

2.3 Minimum Separation Distances from Radio Frequency Sources for Explosives Containing EED

2.4 Storage and Transport

2.5 Storage and Processing Considerations 3 DEPOT SAFE DISTANCE

3.1 Introduction

3.2 Inside Explosive Licensed Buildings 3.3 Mobile Phones and Pagers

4 TRANSPORTATION

4.1 Introduction

4.2 Anti-Theft Tracking Devices

4.3 Emergency Transportation Procedures

Page

References 9

Table

1 Reference Level for Occupational Exposure 2

2 Reference Level for General Public Exposure 3

3 EED RADHAZ Categories 4

Annex

A Sensitivity of EED and their Firing Circuits

B Safe Distance Calculations for use of Radio Transmitting Devices Inside an Explosive Licensed Building

C Electromagnetic Radiation Hazards in Operational Bases

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1 RADIO FREQUENCY HAZARDS TO EEDS 1.1 Introduction

1.1.1 Over recent years there has been a significant increase in the use of electronic communication/detection devices throughout all sections of the community. Types of appliances now in common use range from management/control aids, telemetry, mobile telephones and wireless communication links (Wi-Fi, LANs) to a growing variety of high-powered transmitters covering voice communication, electronic data transmission and radar.

1.1.2 These equipments produce radio frequency (RF) fields of varying intensity according to their output power and antenna gain and are potentially hazardous when used in close proximity to explosives that have an installed electrical means of initiation. This initiation, generally by an electro-explosive device (EED), occurs since most EED function as a direct result of heating the initiating material by an input of electrical energy which can be derived from an external RF field. Annex A discusses the sensitivity of EED and their firing circuits.

1.1.3 To a large extent the sensitivity of EED to extraneous RF fields can be minimized by intrinsic design characteristics, screening and specialized packaging. However, there are a number of circumstances, notably when EED are being transported or handled as a sub-system unpacked, or being tested when they are particularly vulnerable to inadvertent initiation.

1.1.4 The purpose of this chapter is to promote an increased awareness of the potential dangers of operating equipments that produce a RF field in the vicinity of EED among agencies involved with the storage, processing, movement and use of such devices. It includes requirements and advice on the statutory and departmental regulations to be observed and the basic precautions, which should be taken.

1.2 Statutory Requirements

1.2.1 Under existing legislation there is no single statute covering mandatory precautions to be taken when operating equipments producing a RF field in the vicinity of EED. The EU Physical Agents (EMF) Directive will introduce such legislation but implementation has been postponed until 2012. The Health and Safety at Work Act 1974, however, places a general responsibility on employers and those persons in responsible positions to ensure the health and safety of both employees and non-employees, including members of the public, who may be affected by their actions. The “Duty of Care” principle requires that the risk of any hazard being realised shall be reduced to As Low As Reasonably Practicable (ALARP). This chapter identifies procedures that are designed to meet this principle.

1.2.2 MOD regulations concerning exposure of personnel to non-ionising radiation are set out in JSP 375 Vol 2 leaflet 22 (Ref 1) and in JSP 392 (Ref 2). These should be consulted for detailed information and guidance on this aspect of radiation control. However, for information the current guidance on reference levels for personnel exposure is set out in Tables 1 and 2 below.

Frequency Field Strength

V/m Power Density W/m2 1 – 8 Hz 20,000 8 – 25 Hz 20,000 0.025 – 0.82 kHz 500/f (kHz) 0.82 – 65 kHz 610 0.065 – 1 MHz 610 1 – 10 MHz 600/f (MHz) 10 – 400 MHz 61 10 400 – 2000 MHz 3f ½_{(MHz) f/40(MHz)} 2.0 – 300 GHz 137 50

Table 1 Reference Level for Occupational Exposure

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Frequency Field Strength

V/m Power Density W/m2 1 – 8 Hz 10,000 8 – 25 Hz 10,000 0.025 – 3 kHz 250/f (kHz) 0.003 – 1 MHz 87 1 – 10 MHz 87/f ½_(MHz) 10 – 400 MHz 28 2 400 – 2000 MHz 1.375f ½_{(MHz) f/200(MHz)} 2.0 – 300 GHz 61 10

Table 2 Reference Level for General Public Exposure

1.2.3 Publications providing regulations, information and advice on the storage, movement and handling of EED are to be found as indicated below:

(1) NATO: AC 258 Manual on NATO Safety Principles for storage of ammunition

and explosives.

(2) Single Service: Navy Dept: BR 2924. (Ref. 3)

Air Force Dept: DAP 110A-0102 -1D (Ref. 4) and 1E. (3) Joint Service: JSP 800 Defence Movements & Transport Regulations

JSP 800 Vol 4a Dangerous Air Cargo Regulations.

(4) Def Stan: Defence Standard 59-114 Principles of Design and Use of Electrical Circuits Incorporating Explosive Components. (Ref. 5)

(5) British Standards: BS 6657/2002 Assessment of Inadvertent initiation of Bridgewire Electro Explosive Devices by radio-frequency radiation - Guide. 2 SUSCEPTIBILITY

2.1 Factors Affecting Susceptibility

2.1.1 Any length of wire forming all or part of the firing lines to an EED, when placed in a RF field, will act as an aerial and pick up some energy from the field. An electromagnetic hazard would exist if the circuit contained an EED, and the RF level was sufficient to induce a power/ current that was in excess of the no-fire threshold (NFT)1_{power for the device.}

2.1.2 The amount of power fed to a connected EED will depend on the length and configuration of the wires and on the ratio of the source to load impedance of the firing lines and EED. However, unless firing circuits are properly designed sufficient power to fire many EED can be picked up in substantially lower RF field strengths than those experienced during some parts of their service life. The ability of a circuit to pick up power from a RF field can be increased when the circuit is in contact with external conductors such as test cables, tools or fingers. Moreover, when the wires of an EED are separated they may form a more effective dipole antenna and provide an optimum impedance match to the EED giving maximum transfer of power to the EED from the radiation source.

2.1.3 For these reasons, EED separated from their parent system or in systems opened up for maintenance/test are regarded as less safe than when installed into the system as intended by the designer.

1_{The no fire threshold power is defined as the power required to produce a 0.1% probability of fire at the}

95% single-sided lower confidence limit when applied to the EED for a time which is long compared with the thermal time constant (τ) of the device, (i.e. >10 τ).

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2.1.4 The use of ammunition containers e.g. H83 and A480 should NOT be considered to automatically provide sufficient attenuation for EED in isolation or EED contained in non-metallic systems that are not adequately protected.

2.2 EED Testing for Susceptibility to EM Radiation

2.2.1 All complete explosive systems containing EED, which are intended for service use, should be assessed for their susceptibility to RADHAZ. The assessment may be theoretical, based upon the principles in Def Stan 59-114 (Ref 5) (ex OB Pillar Proceeding P101(2)), or a practical trial conducted at a specialist site.

2.2.2 The assessments should cover the susceptibility of EED during preparation, testing, storage and transportation, loading and when loaded to the launcher/platform. These activities are often identified by the categories shown in Table 3:

Categories Activities

1 (Dis)assembly of weapons/stores and testing of sub systems by personnel or machine generally in defence munitions organisation sites.

2 Testing of all up weapons/stores in test houses or along side/on board 3 Storage and transportation of weapons/stores in approved packaging. (Note:

Approved packaging is that identified in the ESTC item listing.)

4 Storage and transportation of weapons/stores not in approved packaging; or whilst handling, assembling, loading/unloading to platform e.g. vehicle, gun, aircraft or launch platform.

5 Weapon/stores loaded to its platform/launcher for its intended use (e.g. to aircraft or in its launcher).

Table 3 EED RADHAZ CATEGORIES

2.2.3 The assessments generally relate to the Minimum Service RF Environment (MSRFE) defined in Def Stan 59-114.

2.2.4 The results of RF susceptibility assessments in terms of maximum safe field strength or power density in various frequency bands are published in BR2924 Vol 2 (Ref 3) for naval systems and many Embarked Military Force items and in DAP 110A-0102-1D (Ref 4) for aircraft systems. Individual system A&ER pamphlets provide safe distance information for land systems where they are not cleared to the MSRFE.

2.2.5 Where no data is published the worst case susceptibility curves at Annex A Figure 2 may be used or guidance can be sought from Defence Ordnance Safety Group (DOSGST3).

2.3 Minimum Separation Distances from Radio Frequency Sources for Weapon/Stores Containing EED

2.3.1 A wide range of equipment emitting RF fields is employed in Service and civil environments. These include broadcast transmitters, communication radios, RF data links, mobile phones, satellite communications, radars, security scanners, remote controls, measurement systems and computer wireless links. These contribute to an increasing level and spread in the RF environment and all must be considered when making RADHAZ assessments.

2.3.2 In some instances this means safe distance restrictions will be required. In particular EEDs/weapons being handled and weapons under preparation, test or maintenance will frequently require procedural controls to ensure they remain safe.

2.3.3 The magnitude of a RF field decreases with increasing distance from the source. The hazard area for transmitters using omni directional or rotating antennae is often defined as a Chap 24 Jan 2013 Page 4

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spherical or right-cylindrical volume centred on the transmitter. For transmitters that have fixed directional beams radiating predominately in one direction (e.g. a satellite tracking system) the hazard area is mainly in the direction of the beam.

2.3.4 The safe distance from Service transmitters for many EED systems, whose susceptibility is known, can be determined by the use of the calculation method shown in Annex A. This requires knowledge of the item susceptibility and the RF transmitter parameters. Data on these for many systems is published in References 3 and 4. For radio systems with known power outputs a simplified procedure is outlined in Annex A. If the data required is not known advice should be sought from DOSG ST3.

2.4 Storage and Transport

2.4.1 EED are encountered in a variety of configurations between their manufacturing stage and their ultimate use or disposal. These configurations range from trade packaging in bulk, Service packaging and sub packages and installation in munitions, to various stages of separate and exposed states that occur in processing and training.

2.4.2 It is important for users to understand how these configurations can influence the basic precautions to be adopted. Transportation and use precautions should also include measures to be covered in emergencies from straightforward vehicle breakdowns to accidents involving fire and/or casualty evacuation.

2.5 Storage & Processing Considerations

2.5.1 Building materials are generally ineffective in affording significant EM protection for EED. Most structures provide no transmission loss from frequencies below 1 MHz but many provide some protection in the form of reflection loss if the polarisation and angle of incidence of the EM energy happens to be favourable, although this is rare.

2.5.2 For all practical purposes it should be assumed that the field strength that exists inside a building is the same as that of any external field. However, if the attenuation of EM radiation, which is provided by a specific building or room, has been determined (for all conditions of doors/windows being opened/closed) then this may be used to determine safe distances from sources of EM radiation.

2.5.3 EED and systems containing EED should only be stored/processed in licensed depot and unit storage and process areas. Siting of these areas should take account of:

(1) The susceptibility of the EED or munitions containing EED during storage or processing as appropriate.

(2) The proximity and radiated power of fixed transmitters in the area. 3 DEPOT SAFE DISTANCE

3.1 Introduction

3.1.1 In depots where weapon processing is being undertaken susceptibility levels may be at their lowest and it is necessary for authorities to understand more fully the RF environment in which the work is being carried out and the interaction with the system firing circuits. The environment will depend on local transmitters both on-site and in the local area.

3.1.2 Transmitters outside the ESA perimeter. Outside the ESA and at least 100 metres from a processing building, radios with a power output of 50 watts or less with no significant antenna gain can be safely used. For higher power radios or radars or shorter distances an assessment will be required to determine the possible field strength in processing areas. For some very high power broadcast transmitters, air traffic control radars or military radars this may require knowledge of their location out to distances of 3 km. The aim should be to ensure that the field strength at any frequency is less than the value shown in Fig 2 of Annex A. For major UK depots DCSA DCTO-CM RSP have agreed to inform relevant responsible persons of new proposals for Jan 2013 Chap 24

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significant RF installations within 3 km. This group should be contacted first concerning local emitters but where questions remain advice may be sought from DOSG ST3.

3.1.3 Transmitters inside ESA. There are a number of portable radios (both hand-held and manpack) in service or being used by contractors/site personnel during maintenance and movement periods and it is likely that they will become more widely used. The use of management radios, data links and RF tags/Wi-Fi etc. is also becoming more common.

3.1.4 In the past, under the ALARP principle, there has been a blanket ban on the use of transmitters within an Explosive Storage Area (ESA) unless specifically approved by DOSG ST3. With the increase of requests for advice on mobile transmitters for security and tracking reasons within ESA and with the advent of Wi-Fi/Bluetooth transmitters in computers and data links (which may be required for use inside process/storage buildings) there is a need to revisit this blanket ban.

3.1.5 The owner/managers of the site must therefore assess all RF transmitters to be used in the vicinity of an EED, or stores containing an EED, for their potential RADHAZ. DOSG ST3 can give specific advice where required. The paragraphs below set out the rules for transmitters inside ESA and licensed buildings:

(1) No deliberate RF transmitters of any power are to be allowed inside an ESA unless they are essential for an activity that is taking place there.

(2) Portable radios, personnel communication equipment, mobile phones, personal electronic devices (PED) or data communications transmitters may be used inside an ESA and external to licensed buildings subject to the requirements of paras 3.1.6 and 3.1.7 being met.

(3) No deliberate RF transmitters are to be allowed inside an explosives building unless meeting the requirements set out in para 3.2 below or specifically agreed by DOSGST3. (4) Assessments shall include safe distance calculations for the transmitters - portable or

fixed.

(5) The minimum safe distance for the use of any transmitter in the vicinity of an EED, no matter what the susceptibility of the explosive nature, shall be 2m even if calculation shows it could be less (unless covered by the rules in para 3.2).

(6) The safe distance applies equally to the use of transmitters in vehicles transporting EED, unless a relaxation has been applied for from the relevant IE who will seek advice from DOSGST3.

(7) Only ATEX certified transmitters classified safe to the relevant standard may be used in areas where an explosive atmosphere (gas/dust) may exist.

3.1.6 For transmitters within an ESA but external to a process building a generic worst-case assessment has to be undertaken. Only essential transmitters should be installed within or taken into an ESA but those that meet the rules below may be allowed without recourse to DOSGST3. (See also sub paras (1) & (2) below.)

(1) All transmitters with a power output of ≤ 1 W, with an aerial gain of ≤ 3 dB, across the frequency spectrum are acceptably safe at a distance of ≥ 10m from the exterior of the buildings.

(2) All transmitters with a power output of ≤ 5 W, with an aerial gain of < 3 dB at a frequency of > 400 MHz are acceptably safe at a distance of ≥ 5m from the exterior of the buildings. 3.1.7 Within an ESA and external to storage buildings where EED initiated items are only stored in their approved ESTC containers (i.e. ordnance not unpacked, handled or worked on) transmitters with a power output of ≤ 25 W, with an aerial gain of ≤ 6 dB, across the frequency spectrum are safe at a distance of 2m from the exterior of the buildings. Due to the possible problems with ensuring that all items remain packed at all times the use of radios at this power level shall only be permitted where absolutely essential and where strong controls are in place and

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can be assured to be in place for the lifetime of the transmitter. Where there is doubt the safety distances and power levels of para 3.1.6 above shall be applied.

3.1.8 For all other transmitters a safe distance calculation shall be carried out as shown in Annex A and the relevant distance imposed.

Notes: (1) Transmitter power is to be taken as maximum the set is capable of emitting – not a level which may be operator or software controlled.

(2) By convention distances rounded up to 2, 5 or 10 m

(3)The above safe distances shall also be maintained between the transmitter and ESA transit routes.

3.2 Inside Explosive Licensed Buildings

3.2.1 Internal to Storage/Processing Buildings. Where transmitters are essential for the operation within a building (e.g. for reading RF tags or data loggers or for laptop Wi-Fi connectivity) the safe distance from explosive stores containing EED shall be calculated as set out in Annex B. Regardless of the distance derived no transmitters with an Effective Isotropic Radiated Power output in excess of 1W shall be permitted inside an explosive process building or 2W in a storage building. Prior to deployment of any transmitter approval should be sought from the relevant IE and the calculations should be checked by DOSGST3. Strict controls shall be put in place to ensure the safe distances are always maintained. Where multiple transmitters are required in a building (e.g. for RF tags/loggers) advice shall always be sought from DOSG ST3.

3.2.2 The Bowman Personal Role Radio (PRR) has been assessed as being safe for use by personnel handling in-service explosive items. No further control is therefore required for them except in process areas where the rules of Annex B should be applied and the normal requirements for CAT A, B and C areas shall be followed.

3.3 Mobile Phones and Pagers

3.3.1 Use of mobile phones and pagers must be controlled in the vicinity of munitions. As their power output is unpredictable and can be well in excess of 1W. Mobile phones and pagers shall NOT be used:

(1) In explosive storehouses (ESH) / potential explosion site (PES) / magazine/ weapon stowage areas/explosive process buildings.

(2) Close to ordnance under preparation.

3.3.2 Subject to the above, essential mobile phones and pagers are permitted to be used in other areas provided that:

(1) Only standard handheld phones/pagers are used.

(2) Minimum separation distances as calculated in accordance with paras 3.1.6 and 3.1.7 or Annex A are adhered to.

(3) Explosive vapour/dust hazards do not exist.

4 TRANSPORTATION 4.1 Introduction

4.1.1 It is not practicable to achieve a safe EED environment during transportation through the observance of calculated safe distances. For this reason, all EED and systems containing EED offered for transportation should be assessed as safe to the Minimum Service RF Environment for sea and air transportation or a field strength of at least 200 V/m (~100 Wm-2_{) at all frequencies for}

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road transportation. (N.B. Any area around a transmitter where the field strength may exceed the levels shown in Table 2 should not be accessible to the general public.)

4.1.2 Service EED and systems containing EED which have not been cleared to an EM environment of 100 Wm-2 _{or the MSRFE (as appropriate) must be protected during transit by} enclosure in a metal box or by approved materials providing sufficient screening. Specific instructions on munitions incorporating EED which are either cleared or not cleared for transportation with respect to RF protection are to be found in Service publications discussed at paragraph 2.2.4.

4.1.3 Where the munitions are required to be closer than a minimum of 2 m from a vehicle transmitting antenna advice should be sought from DOSG ST3. Dependent on the power output, frequency and cable routing this may in some cases be reduced to 0.2 m for systems assessed as safe in the MSRFE.

4.1.4 When it is considered necessary to transport systems containing EED of unknown susceptibility, the worst case susceptibility curve at Figure 2 of Annex A may be used. All personnel engaged in the carriage of such articles should be aware of RF hazards and observe consignor’s instructions fully. Note should be made of any special instructions covering loading/unloading/handling when EED are most vulnerable to EM radiation.

4.2 Anti Theft Tracking Devices

4.2.1 Vehicle tracking devices of various types and fulfilling various functions are now common place on vehicles used not only by contractors but also on a variety of MOD vehicles. These tracker systems are no longer used purely for tracking stolen vehicles but are more generally used to monitor vehicle movements as well as driver profiling. Such tracker systems are often present without the driver’s knowledge and hence the type and function of such systems are known only to the organisation undertaking the vehicle monitoring function. As a result of this increase in use and function of vehicle tracker devices a number of different systems are now commonly used and whilst all utilise GPS for vehicle positioning various methods of communicating between the vehicle and central monitoring facility are used (eg. GSM, VHF & UHF).

4.2.2 Vehicles carrying tracker devices shall not be taken into explosives buildings except in specific areas identified for loading/unloading of packaged (or aircraft prepared) munitions or within an appropriately licensed explosives building for overnight or short period parking as permitted within the constraints of the explosive licence (not applicable to EOD vehicles/garages). The safe distances as advised in Table 4 should be observed for the relevant state of the munition(s). Where the 10m safe distance from damaged/disassembled stores is not practical in particular establishments DOSG should be provided with the list of weapons which may be involved to determine if this distance can be reduced from the worst case value. Where a vehicle has been involved in an accident and its explosives contents are damaged (or potentially damaged) then advice should be sought from DOSG if practicable.

Packaged Safe Distance (metres) Unpackaged Safe Distance (metres) Damaged or disassembled Safe Distance (metres) 0.25 3 10

Table 4 Safe Distances to be Observed

4.2.3 Note that for stores which are in a packaged condition on a vehicle the transmit antenna should not be within 0.25 m of any electrically initiated item. It is the responsibility of the vehicle user and the vehicle supplier to ensure that the location of the transmit antenna is identified so that the distance to any explosives can be determined.

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4.2.4 The term “Packaged” in this instance means the explosive item is contained within its ESTC approved packaging. This equates to Category 3 as described in Table 3.

4.2.5 The term “Unpackaged” in this instance means the explosive item has been removed from its ESTC packaging but remains in an assembled or all-up-round state or forms part of a complete assemble. This is also applicable to items installed on a platform. This equates to Category 4 (or Category 5 for items installed on a platform) as described in Table 3.

4.2.6 The term “Damaged or Disassembled” in this instance means the explosive is not in its ESTC packaging and is physically damaged or is broken down for test and/or assembly purposes, ie. typical activities undertaken within a processing facility. This equates to Categories 1 and 2 as described in Table 3.

Emergency Transportation Procedures

4.2.7 In the event of an incident/accident during transportation of munitions, items which do not normally present a high RADHAZ risk may become acutely vulnerable if there is damage to their inherent protection, i.e., structural or packaging. Pending a detailed inspection the under mentioned restrictions on RF transmissions in the immediate vicinity should be imposed immediately:

(1) No RF transmission is to be allowed within a radius of 10 metres from the EED.

(2) Emergency services using radios with EIRP greater than 5 watts should not transmit within 50 metres of the damaged equipment. (EIRP = Effective Isotropic Radiated Power)

(3) Drivers and/or escorts in vehicles transporting EED should be issued with the “Notice to Crews of Road Vehicles carrying Military Explosives including Ammunition” (example, see JSP 445) that details actions to be taken in the event of an incident/accident.

REFERENCES

1 JSP 375 Health and Safety Handbook Vol 2 Leaflet 22 Safety in the Use of Electromagnetic Radiation

2 JSP 392 Radiation Safety Handbook

3 BR2924 Radio Hazards in Naval Service Volume 2

4 DAP110A-0102-1D 3rd_{Edition dated Nov 03 & -1E 2}nd_{Edition dated Nov 00}

5 Def Stan 59-114 Principles of Design and Use of Electrical Circuits Incorporating Explosive Components.

6 DOSG Div Note 77/2005 dated 07/03/05 7 DOSG Div Note 75/2005 dated 16/02/05

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CHAPTER 24

ANNEX A

SENSITIVITY OF EED AND THEIR FIRING CIRCUITS

CONTENTS Para

1 SENSITIVITY OF EED AND THEIR FIRING CIRCUITS 1.1 Introduction

2 ELECTRO-EXPLOSIVE DEVICES

2.1 Main Types of EED in Use and Their Properties 2.2 EED Sensitivity Thresholds

2.3 Transmitter Characteristics 2.4 Safe Distance Calculations

Table Page

1 The Minimum Service Radio Frequency Environment 2

2 Example EED No Fire Thresholds 3

3 Quick Reference – Minimum Separation Distance (metres) for Radios up to 1GHz 4 1 SENSITIVITY OF EED AND THEIR FIRING CIRCUITS

1.1 Introduction

1.1.1 An EED can be a component of a munition system or subsystem having no separate existence during the munition life cycle save during manufacture, refurbishment or disposal. Alternatively an EED may be fitted into a munition system in the field such that it is stored and transported as a separate item, (e.g. an electric detonator fitted to a demolition charge).

1.2.1 The energy to initiate an EED (either directly or via coupling electronics) may be from the intended source or accidentally by pick-up from RF transmitters.

1.3.1 Radio and radar transmitters throughout the world operate over a wide frequency spectrum. The RF environment in which service equipments should be designed to remain safe (and in some cases operate) is given in Def Stan 59-114. This is often known as the ‘Minimum Service RF Environment’ (MSRFE). (Note this has replaced STANAG 4234 since recent evidence has shown the need to re-define the levels that may be experienced in some situations. The new levels will be applied to new design/procured equipments only and assessments to the previous level remain valid). However not all systems/EED meet these levels in all operational configurations and some transmitters may exceed these environments at close range.

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Field Intensities

STANAG 4234 Def Stan 59-114 Frequency Vm-1 Wm-2 (average) Vm-1 Wm-2 (average) 200 kHz - 525 kHz 300 200 525 kHz – 2 MHz 200 200 525 kHz - 32 MHz 200 200 32 MHz - 150 MHz 10 30 150 MHz - 225 MHz 100 80 225 MHz - 400 MHz 50 100 400 MHz – 790 MHz 50 50 790 MHz - 1GHz 1000 150 1 GHz – 2.5 GHz 1000 1000 2.5 GHz – 4.5 GHz 1000 2400 4.5 GHz – 6.0 GHz 1000 500 6.0 GHz – 8.0 GHz 1000 1500 8.0 GHz – 12 GHz 1000 1500 12 GHz – 18 GHz 1000 1500 18 GHz - 40 GHz 100 500

Table 1 The Minimum Service Radio Frequency Environment 2 ELECTRO-EXPLOSIVE DEVICES

2.1 Main Types of EED in Use and Their Properties

2.1.1 Those EED in current and envisaged service use can be divided into 2 groups, low voltage and high voltage types. In general, these can be sub-categorised into 3 broad types:

(1) Low voltage devices with long thermal time constants (typically 10ms - 50ms) such as bridgewire (BW) devices that are known commonly as “power sensitive”.

(2) Low voltage devices with short thermal time constants (typically 1μs-100μs) such as Film Bridge (FB) and Conducting Composition (CC) which are known commonly as “energy sensitive”.

(3) High voltage devices with a secondary explosive such as Exploding Bridgewire (EBW) and Exploding Foil Initiator (EFI) devices which require a fast, high voltage discharge pulse to initiate them. These are commonly known as “HV devices”.

2.2 EED Sensitivity Thresholds

2.2.1 Power sensitive devices tend to integrate transient energy and, in the case of repetitively pulsed radars will respond to mean or average power levels. LV energy sensitive devices tend to respond to the peak power level of an electrical transient/pulse and pulse stream (e.g. pulsed radar) and this must be taken into account when determining their susceptibility. HV devices are generally considered to require such a specialised, fast rising pulse that accidental initiation from a radio or radar field is not credible and assessments are against accidental dudding.

2.2.2 Whilst the above groups describe the salient characteristics of each type of EED it should not be inferred that they react exclusively to either power or energy impulses. In determining hazard thresholds (known as No Fire Thresholds (NFT)) both types of reactions are considered. To illustrate the results a typical BW EED (igniter Type F53) and a typical CC device (type M52) NFT figures are shown in the following table.

Chap 24 Annex A Jan 2013 Page 2

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Radio Frequency Hazards To JSP 482 Edition 4 Electro-Explosive Devices EED Resistance Range (Ohms) NFT Power (mw) NFT Energy (mj) Time Constant (ms) Igniter Type F53 0.9-1.6 130 2.3 18 M52 CC Igniter 1k – 1.2M 14 0.0022 0.157

Table 2 Example EED No Fire Thresholds 2.3 Transmitter Characteristics

2.3.1 There are a number of radios and data communication links in service or being used by contractors/site personnel for maintenance and operations and it is likely that use of the RF spectrum will continue to increase.

2.3.2 RF transmitters should not be used in areas of munition handling or in the vicinity of munition routes when stores are being handled, during loading/unloading and close to stores loaded to a launcher without proper consideration of their safety. Some simple worst-case safety distance rules for transmitters are given in the main section of this chapter and these should be applied if possible. Where these rules are not capable of being met or where more detailed assessments are required a safe distance shall be calculated and applied as shown below.

2.3.3 Transmitters in Service use are listed in Single Service publications produced under RN, Army and RAF arrangements. The Navy (Ref 3) and the RAF (Ref 4) publications present field strength against distance graphs for high power microwave transmitters. Where these graphs are not available or do not show the relevant system the following information is the minimum required to calculate their field strengths:

(1) Type of aerial (directional or omni-directional).

(2) Mean and peak power fed to the transmitter antenna (watts). (3) Frequency or frequency band of the transmitter.

(4) For a directional antenna the antenna gain.

2.3.4 This information is generally available in the equipment handbooks or from the appropriate agencies/manufacturer.

2.4 Safe Distance Calculations

2.4.1 It is then necessary to obtain the susceptibility level (at the transmitter frequency) of the relevant store(s) or use a worst case assessment. Susceptibility levels for most in-service stores are listed in Refs 3 & 4 or for many Army systems in the relevant AESP. Once susceptibility levels have been ascertained, it is then possible to translate this information into minimum separation distances (hazard area) from radio and radar transmitters. There will generally be a number of minimum distances to allow for the type of activity being undertaken.

2.4.2 Where the transmitter information and the susceptibility of the EED is known then the formula below may be used to derive a safe distance.

S

PG

D

π

4 =

metres Where:

D is safe distance in metres

P is average transmitter power in watts

G is antenna gain (as a linear number NOT dB)

S is susceptibility level of EED/store in W/m2_{(at the frequency of the transmitter)}

2.4.3 If the EED is an energy sensitive device then a multiplication factor needs to be included to take account of the transmitter pulse characteristics and the EED thermal time constant. These Jan 2013 Chap 24 Annex A Page

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calculations become relatively complex and advice should generally be sought from DOSG ST3. The method is however documented in references 3 & 4 for those who wish to undertake their own calculations. (Note: this factor is generally only relevant for microwave pulse transmitters such as radars). The only systems in service at time of publication of this JSP that have LV energy sensitive EEDs are: Aden, Mauser and Phalanx cannon rounds, TVE (for 120mm gun) and the 4.5” Naval Shell. References 3 & 4 contain full susceptibility data for these items.

2.4.4 Alternatively for typical radio systems the lines in Figure 1 may be used to determine the safe distance for an EED with a known susceptibility.

2.4.5 Again for radio systems only, where the transmitter information is known, but the susceptibility of the munition is unknown, reference may be made to Table 3 to determine the safe distance from the most sensitive store being used and handled in its normal service configuration (including handling of EOD detonators). Where a store has been damaged or dismantled the safe distance should be calculated using the safe power density derived from the red line on the graph at Figure 2. The distances can be used for frequencies up to 1 GHz but above about 60 MHz the distances will be pessimistic and more realistic figures will generally be found by calculation using the graph at Figure 2 to determine the susceptibility of a worst case undamaged store (red line) or a worst case damaged/disassembled store (blue line).

2.4.6 The safe distances determined under this publication are subject to any over-riding limitation laid down elsewhere for the protection of personnel against the biological effect of RF radiation.

TRANSMITTER POWER IN WATTS ANTENNA GAIN RATIO (dBi) 1 W 4 W 6 W 10 W 15 W 25 W 30 W 50 W UNITY (0) 5 m 10 m 13 m 17.5 m 20 m 26 m 28 m 36.5 m SPECIAL (2) 6.5 m 13 m 16 m 20.5 m 25 m 32.5 m 35.5 m 46 m STANDARD (3) 7.5 m 15 m 18 m 23 m 28 m 36.5 m 40 m 51.5 m HIGH GAIN (5) 10 m 18.5 m 22 m 29 m 35.5 m 46 m 50 m 65 m

Table 3 Quick Reference Minimum Separation Distance (metres) for Radios up to 1 GHz

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Jan 2013 Chap 24 Annex A Page

5

Intentional Blank Page

0.001 0.01 0.1 1 10 100 1 10 100 1000 Distance (m) Susceptibility W/m^2 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Field Strength V/m 60 20 6 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Antenna TRANSMITTER POWER in Watts

Gain dB 1 5 10 15 20 25 30 50 100 0 1 3 4 5 6 7 8 10 12 2 2 5 8 0 11 13 3 2 4 6 8 9 10 11 12 13 5 3 5 8 10 11 11 11 13 14 6 3 6 9 11 11 13 13 14 14 4 7 9 1

Fig. 1 RF Power Density Hazard Graph for Radios (Frequencies from 60 to 500 MHz) Note: 1 Determine appropriate line from table using transmitter power and antenna gain. Read across from EED susceptibility to relevant line and down to see safe distance.

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0.0001 0.001 0.01 0.1 1 10 100 1000 10000 0.1 1 10 100 1000 10000 100000 Frequency MHz Sa fe Pow e r D e n s it y W /m 2 Damaged/disassembled Worst Case In-service store

(being handled)

Figure 2: Worst Case Susceptibility for In-service Stores

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CHAPTER 24

ANNEX B

SAFE DISTANCE CALCULATIONS FOR USE OF RADIO TRANSMITTING DEVICES INSIDE AN EXPLOSIVE LICENSED BUILDING

CONTENTS

Para

1 INTRODUCTION 2 REQUIREMENTS

Table Page

1 Transmitter parameters with minimal safe separation distances 2 1 INTRODUCTION

1.1 As noted in the main body of this chapter new applications for modern technology are driving a requirement for a variety of wireless transmitters to be used inside explosive storage and process buildings. Such applications range from data loggers, environmental monitors and Wi-Fi enabled laptops through to readers for loggers/recorders and data links to remote control positions. Many such applications are becoming essential for the operation of a facility and so regulations under which the transmitting devices may be permitted inside a building are required.

2 REQUIREMENTS

2.1 Individual radio transmitters may be permitted inside an explosive storage and process building subject to the following:

(1) No transmitter may have an Effective Isotropic Radiated Power (EIRP) output of greater than 1 Watt for use in a process area or 2 watts for use in a storage area. (Note EIRP = output power x antenna gain).

(2) Unless agreed in advance by DOSG ST3 items to be placed inside weapon storage containers shall have an EIRP < 50 mW and shall operate at a frequency > 2000 MHz. (3) A worst case safe distance shall be calculated for each item as shown below and the item

shall carry a label clearly showing this distance.

(4) Portable transmitters inside a process area shall not require a safe separation distance of more than 1 metre, as determined by the method outlined below. Items requiring a greater safe separation distance shall be permanently fitted and a full assessment carried out to ensure the safe distance will always be maintained from all electrically initiated stores. (5) The equipment shall meet the same electrical standards as required by other items

relevant to the Category of the building (see Chapter 8).

(6) Where multiple transmitters are required in a building (e.g. for data loggers or RF tags) advice shall always be sought from DOSG ST3.

2.2 Transmitters with an EIRP of 5 mW or less at any frequency do not require a safe

separation distance. Above 400 MHz transmitters with greater power output can be permitted with Jan 2013 Chap 24 Annex B

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Chap 24 Annex B Jan 2013 EED or firing line.) These levels are shown in Table 1.

EIRP milliWatts Frequency Safe Separation Distance

< 5 Any Near touching

5 ≤ EIRP < 10 ≥400 MHz 10 cm

5 ≤ EIRP ≤ 50 ≥2000 MHz Near touching

Table 1 Transmitter parameters with minimal safe separation distances

(Note: Near touching is defined as in close proximity to a firing circuit or EED but the transmitter case or antenna should not touch the wires or EED.)

2.3 For transmitters with an antenna that is not omnidirectional (i.e. gain >1.6 dB) the safe distance will need to be determined by measurement and DOSG advice shall be sought on the method to be used. For all other transmitters a safe separation distance shall be determined using the method set out below.

(1) Establish power reduction ratio from transmitter output power (PT) to maximum allowable power received (PR). If PR / PT is less than 0.04 use the formula at paragraph 2.4 to calculate safe distance. (For PR use a value of 2.5mW)

(2) If PR / PT is greater than 0.04 use the graph at Figure 1 look up spacing required (in wavelengths) for PR / PT.

(3) Calculate safe separation distance in metres equivalent to this value using formula below: Safe separation distance = spacing (wavelengths) x 300 / f metres

Where f = frequency in MHz

(4) Where the safe separation distance is less than 0.02 m (2 cm) it can be reduced to near touching.

2.4 Where PR / PT is less than 0.04 the safe distance can be calculated using the formula:

D = 2 x λ x SQRT(PT x GT)

Where D is safe separation in metres PT is transmit power (watts)

GT is transmit antenna gain (as a ratio not in dB)

2.5 It is important for this assessment that the values used for PT and GT are the maximum possible for the family of devices. They should be determined by measurement rather than from manufacturer’s claims. If no measurements are available a factor of at least 3 dB shall be added to a specification figure. For Transmitters in which the power output is controlled manually or by software the maximum power capability of the RF circuit shall be used in all calculations and measurements. Where the distance determined is deemed to be not practical in use a

measurement using the method defined in Ref 12_{shall be performed. The specialist antennas} required may be constructed by a competent test house (after consultation with DOSG ST3) or DOSG ST3 can recommend companies capable of making the measurements. An alternative test method in which the E field is measured by use of a 3-axis probe may be used at frequencies

2

Thales Report RHD 1999. Test Method for Measuring the Hazard from Low Power RF Devices. April 2007

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above 100 MHz. DOSG ST3 should be consulted on this method. The distance at which the E field falls below the level shown in figure 2 shall be taken as the safe separation distance.

2.6 The distance determined must be clearly displayed on the transmit device and procedures put in place to ensure this distance is maintained from any EED.

0.010 0.100 1.000 0 0.1 0.2 0.3 0.4 0.5 0.6 Spacing (Wavelengths) P o w er T ra n sf er R ati o (P R /P T )

Figure 1: Power Transfer Ratio vs Spacing

Figure 2: Maximum Electric Field vs Frequency

Jan 2013 Chap 24 Annex B Page

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Chap 24 Annex B Jan 2013 Intentional Blank Page

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CHAPTER 24

ANNEX C

ELECTROMAGNETIC RADIATION HAZARDS IN OPERATIONAL BASES

CONTENTS Para

1 INTRODUCTION

2 GENERAL

3 SAFETY OF THE ELECTRO-EXPLOSIVE DEVICE 4 SAFETY DURING STORAGE AND TRANSPORT

5 SAFETY DURING HANDLING

Table Page

1 Safe Distances for ESTC Approved Packaged Stores Cleared to MSRFE 3

2 Safe Distances for Handling Undamaged Stores 5

3 Worst Case Safe Distances for Undamaged Stores/EED – for Radios up to 1 GHz 5 1 INTRODUCTION

1.1 The guidance contained in this Annex is aimed at operational scenarios and is principally relevant to army deployments since the regulations concerning RN ships and RAF bases are contained in BR 2924 Vol 2 and DAP110-0102-1D and –1E respectively.

1.2 This Chapter does not include the precautions to be taken when operating, connecting or loading weapons/stores containing EED. Such regulations are contained in the user handbook or are issued by the user arm concerned (see references in para 1.1 for RN and RAF use).

1.3 No user knowledge of weapon susceptibility or transmitter parameters is assumed. Further information is available on this from the local Explosives Technical Authority (see Chapter 1 Annex B). In addition Annex A to this chapter contains the method for calculating safe distances for systems including worst case calculations when necessary.

1.4 In all cases of difficulty, advice may be obtained from the Ammunition Technical Officer (ATO)/ (RN, RAF or Civilian Equivalent) or for specialist advice consult DOSGST3.

2 GENERAL

2.1 Relatively little power is required to fire many EED and they will normally respond to either a direct or alternating current signal. EED will therefore respond and fire when sufficient EM energy is coupled into the firing circuit to which they are connected even when there is no power supply. This energy may radiate from an antenna of a radio, radar or other transmitter or be generated as a transient from other electrical equipment.

2.2 The protective switch, which prevents the initiation of an EED by the firing circuit until the desired time, does not prevent pick-up of rf energy on the wiring between the switch and the EED. Moreover, if the switch is electronic it may not provide a break to energy at microwave frequencies.

Jan 2013 Chap 24 Annex C Page 1

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discontinuity in its skin (e.g. inspection windows, GRP casings, joints). The degree of screening provided by packaging will depend on the conductivity of the material used and the presence of slots or joints for lids etc.

2.4 The use of ammunition containers e.g. H83 and A480 should NOT be considered to automatically provide sufficient attenuation for EED in isolation or EED contained in non-metallic systems that are not adequately protected – although they do provide adequate shielding in many situations relevant to army operations.

2.5 In general, stores containing EED are more susceptible to EM energy pick-up when

removed from their container and when being handled, loaded and unloaded into/from weapons or platforms.

2.6 The ability of a firing line to pick up sufficient energy to cause an EED to operate depends on many factors. These include the electrical characteristics of the EED, the nature of the firing line, its length and geometry, the EM field strength and the frequency transmitted. The EM field strength is dependent upon the power output of the transmitter, the characteristics of the antenna system and the distance between the antenna and the firing circuit. In a large system it is not the position of the EED that is important, but the position of the whole firing circuit in relation to the EM field.

3 SAFETY OF THE ELECTRO-EXPLOSIVE DEVICE

3.1 All in-service stores containing an EED are assessed for their susceptibility to RF when packaged in their ESTC approved container, when being handled and where relevant when loaded to a weapon launcher. Such assessments attempt to demonstrate clearance to the Minimum Service RF Environment (MSRFE) which is deliberately set at a high level.

3.2 At all stages in their life it is essential that stores containing EED are not exposed to a RF environment exceeding their safe limit. For items in their ESTC approved packaging and cleared to the MSRFE there are only a few transmitters in land service use which require safe distance restrictions. These are listed in Table 1. (Note, however, that such radios are prohibited from use in explosive storage buildings and prior approval is required for radios in explosives storage areas (ESA)).

3.3 Even where no restrictions are shown in Table 1 it is not good practice to place electrically initiated ordnance in close proximity to a transmitting antenna. A safe distance of at least 2m is therefore recommended as being the minimum that should be applied whenever practical.

Chap 24 Annex C Jan 2013 Page

2

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Frequency Band Common Army Radio Types Safe Distance (metres) HF (1.5 – 30 MHz) TRC – 521, D11/R230/234 D13/R234(2) BOWMAN PRC 325, 327, VRC 328, 329 2 VHF (30 – 225 MHz) Ptarmigan SCRA VRC – 470 T404/R404 Radio Relay C41/R222 BOWMAN PRC 354, 355, 356, VRC 357, 358, 359 3 V/UHF (225 – 790 MHz)

Radio Relay TRC–471 TRIFFID I & II

C50/R236, C70

4

SATCOM V/UHF PSC – 505, 510 3

SATCOM (I Band) VSC – 501, TSC – 502 5*

RADARS Rapier, Cymbeline, AN/TQP-37, LCMLR

10*

RADARS Mamba, Cobra 150*

Table 1 Safe Distances for ESTC Approved Packaged Stores Cleared to MSRFE

* These distances assume illumination by the main beam of the transmitter. Where this can be assured not to occur the distance may be reduced to 3m except for Cobra where 15m shall be applied.

NOTE:

(1) Where an in-service transmitter is not included a safe distance of 2m can be used for all radios with an output power of less than 25 watts. For all other transmitters a safe

distance calculation must be done using data either in the relevant publication for the store or in BR2924, DAP-110A-0102-1D/1E. In case of difficulty consult DOSGST3.

(2) For vehicles fitted with radios and having designated stowage positions for electrically initiated ordnance, assessments are carried out to ensure that the nominated weapons will remain safe. The above distances do not therefore apply to such weapons and stowages. 4 SAFETY DURING STORAGE & TRANSPORT

Jan 2013 Chap 24 Annex C 4.1 During storage and transport all items should remain packed in their ESTC approved

containers. The safe distances noted in Table 1 shall be applied during storage and transport. The distances apply to radios fitted to a vehicle carrying the store, and to transmitters which may be encountered on route. (Note, however, that for service vehicles with fitted radios and designated stowage positions individual assessments of RADHAZ safety are conducted during vehicle design to ensure they remain safe.) This is relevant whether movement is by land, sea or in the air but

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service radios, which may be encountered during transport on public roads etc, the personnel RADHAZ levels will be more restrictive. Packaged ordnance will therefore be safe unless taken inside a personnel RADHAZ boundary. Electrically initiated stores not packed in their ESTC approved manner may be more susceptible. Individual system publications should contain guidance where greater safe distances are required. Where this is not known the

distances/precautions given below for handling should be followed unless further information is obtained.

5 SAFETY DURING HANDLING

5.1 When stores containing EED are removed from their package, the susceptibility to EM pick-up may increase and larger safe distances may be necessary. Individual A&ERs should be

consulted for any restrictions imposed. Where these are not available, or there is doubt, worst case distances from in-service radios are given in Table 2. These distances have been calculated using the maximum likely susceptibility for any undamaged store. For most stores this will be very pessimistic and where this creates a problem DOSGST3 should be consulted for detailed advice. It should be noted that the distances in Table 2 do not apply to radio or radar equipment

associated with a store in its systems environment (e.g. guided missiles and their tracking equipment), nor do they apply to demolition firing circuits which have already been connected to the detonator. In these cases the user arm concerned will issue instructions.

5.2 In order to allow units to make their own assessments for management and other radios which may be in use locally the distances obtained from Table 3 below may be used. This requires basic knowledge of the radio concerned but again is based on pessimistic assumptions related to handling an in-service detonator to calculate the minimum safe distance. These figures may be used at radio frequencies up to 1 GHz.

4

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Frequency Band Common Army Radio Types Safe Distance (metres) HF (1.5 – 30 MHz) SR 718 U5, BOWMAN PRC 325, 327, VRC 322, 328, 329 60 HF (1.5 – 30 MHz) TRC – 521, SR D11/R230/234, SR D13/R234(2) 150 VHF (30 – 225 MHz) SR PF85 PFX, SR EX PF85C, SR MX294, VRC 301, SR F494, SR FM914PM, VRC 390/391, GRC 391, CQP 813/833 FRC 395 (TA4523L&H), FRC 398 (4525L&H) VRC 396 (TA4523L&H) PRC 397 (TA4523L&H) SR AN/ARC 340, SR AD 120, SR SRM 4515, SR STR 38, SR AN/ARC 44 BOWMAN PRC 354, 355, 356, VRC 357, 358, 359 40 VHF (30 – 225 MHz) Ptarmigan SCRA VRC 470, SR T404, SR T406 Radio Relay C41/R222 100 V/UHF (225 – 790 MHz) PRC 344/392, SR PF85 PFX, SR EX PF85C, SR MX 296, SR T414, SR F496, CQP 863, FRC 395 (TA4523U), VRC 396 (TA 4523U), FRC 398 (SRM 4525U), SR PTR 1751/170,

10

V/UHF

(225 – 790 MHz)

Radio Relay TRC–471 TRIFFID I & II

C50/R236, C70 50

V/UHF PSC – 505, 510, TRC 471 TRIFFID III, BOWMAN HCDR

30

SHF TRC 481 PTARM SHF 3

SATCOM (I Band) VSC – 501, TSC – 502 15

RADARS Rapier, Cymbeline, AN/TQP-37, LCMLR 30

RADARS Cobra, MAMBA 600

Table 2 Safe Distances for Handling Undamaged Stores TRANSMITTER POWER IN WATTS ANTENNA GAIN RATIO (dBi) 1 W 4 W 6 W 10 W 15 W 25 W 30 W 50 W UNITY (0) 5 m 10 m 13 m 17.5 m 20 m 26 m 28 m 36.5 m SPECIAL (2) 6.5 m 13 m 16 m 20.5 m 25 m 32.5 m 35.5 m 46 m STANDARD (3) 7.5 m 15 m 18 m 23 m 28 m 36.5 m 40 m 51.5 m HIGH GAIN (5) 10 m 18.5 m 22 m 29 m 35.5 m 46 m 50 m 65 m

Table 3 Worst Case Safe Distances for Undamaged Stores/EED – for Radios up to 1 GHz

Jan 2013 Chap 24 Annex C Page 5

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in Table 2. Where these distances are not practical or the transmitter is not listed actual susceptibility figures must be obtained from A&ERs or from DOSGST3 and the safe distance calculated in accordance with Annex A.

5.4 The Bowman Personal Role Radio (PRR) has been assessed by the DOSG as being safe for use by personnel handling in-service explosive items and so no further control is required for them (except they are not suitable for use in flammable/explosive atmospheres and in magazines and explosive storage buildings).