U.S. Fire Administration Voice Communications Guide for the Fire Service - FEMA

8/9/2019 U.S. Fire Administration Voice Communications Guide for the Fire Service - FEMA

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U.S. Fire Administration

Voice Radio

Communications Guide

for the Fire ServiceOctober 2008


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U.S. Fire Administration

Mission Statement

We provide National leadership to foster a solid foundation

for local fire and emergency services for prevention,

preparedness and response.


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Dear Members,

Radio communications or the fre service has evolved considerably over the last 60 years.Radios that were once rerigerator-sized monsters are now small enough to ft in the palm o

the hand.It used to be that only the company ofcer was permitted to use a radio. Today, radios are acritical saety tool that must be in the hands o every fre fghter at every emergency scene. Asadvances in radio communication technology occur, its important to make sure that radiosremain an eective and reliable means o communication.

Specifcally, new technology or radio communication systems must meet the unique demandso the job o fre fghting. Fire fghters must be able to communicate in cold and hot temperatureextremes, in wet and humid atmospheres ull o combustion byproducts and dust, whileunder or above ground, inside and below buildings and in rubble piles. Other environmentalchallenges include loud noise rom apparatus, warning devices, tools and the fre itsel. Anynew radio communication system must take these actors into consideration.

The IAFF has made it a priority to ensure that everyone goes home sae at the end o each shit.Because radios are one o most important pieces o saety equipment, we expect that any newcommunications system will be eective, sae, reliable and simple to use.

I urge every IAFF afliate to be involved early on in the process o developing a new radiocommunication system in their jurisdiction to make sure that the unding, stafng, training,testing, trouble-shooting and implementation meet the standards and requirements or frefghters to respond saely and eectively.

This Manual is designed to help afliate leaders and members understand new communicationand radio system issues in order to remain inormed players in the process.

An eective communications system requires proper planning at the ront end in order to prevent

problems later, and there is no one better to participate in the process than fre fghters.

Stay sae,Harold A. SchaitbergerIAFF General President

International Association of Fire

Fighters, AFL-CIO, CLC


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ACknOwLedgement

The United States Fire Administration (USFA) is committed to using all means possible or reducing theincidence o injuries and deaths to reghters. One o these means is to partner with organizations thatshare this same admirable goal. One such organization is the International Association o Fire Fighters(IAFF). As a labor union, the IAFF has been deeply committed to improving the saety o its membersand all reghters as a whole. This is why the USFA was pleased to work with the IAFF through acooperative agreement to develop this Voice Radio Communications Guide or the Fire Service. The USFA grateullyacknowledges the ollowing leaders o the IAFF or their willingness to partner on this project:

Assistant to the General President

Occupational Health, Saety & Medicine

Richard M. Duy

International Association o Fire Fighters, AFL-CIO, CLCDivision o Occupational Health, Saety and Medicine

1750 New York Avenue, NW

Washington, DC 20006

(202) 737-8484

(202) 737-8418 (FAX)

www.ia.org

The IAFF also would like to thank Lei Anderson, Deputy Chie, Phoenix Fire Department; Jim Brinkley,IAFF Director o Occupational Health and Saety; Joseph Brooks, Radio Supervisor, Boston Fire Department;Missy Hannan, Senior Graphic Designer, International Fire Service Training Association (IFSTA)/FireProtection Publications, Oklahoma State University; Tim Hill, Captain, Phoenix Fire Department andPresident o the Proessional Fire Fighters o Arizona; Christopher Lombard, Lieutenant, Seattle FireDepartment; Andy MacFarlane, Phoenix, Arizona; Brian Moore, Captain, Phoenix Fire Departmentand Director o Member Benets, IAFF Local 493; Kevin Roche, Assistant Fire Marshal, Phoenix FireDepartment; Mike Wieder, Assistant Director, IFSTA/Fire Protection Publications, Oklahoma StateUniversity; and Mike Worrell, Captain, Phoenix Fire Department, or their eorts in developing thisreport.

General President

Harold A Schaitberger

General Secretary-Treasurer

Vincent J. Bollon
http://www.iaff.org/http://www.iaff.org/


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TABLE OF CONTENTSSECTION 1 INTRODUCTION ................................................................................................................................1

Purpose .................................................................................................................................................................1

Why the Fire Service is Dierent ..........................................................................................................................1

SECTION 2 BASIC RADIO COMMUNICATION TECHNOLOGY ..........................................................................3

Radio Spectrum ....................................................................................................................................................3

Channel Bandwidth ..............................................................................................................................................5

Radio Wave Propagation .......................................................................................................................................5

Intererence ..........................................................................................................................................................8

What Aects System Coverage? .............................................................................................................................9

Summary ............................................................................................................................................................12

SECTION 3 RADIOS AND RADIO SYSTEMS .......................................................................................................13

Analog Radios .....................................................................................................................................................14

Digital Radios .....................................................................................................................................................15

APCO P25 ...........................................................................................................................................................17

Direct and Repeated Radio Systems.....................................................................................................................19

Simulcast Transmitter Systems ............................................................................................................................23

Operational Considerations ................................................................................................................................24

SECTION 4 PORTABLE RADIO SELECTION AND USE .......................................................................................27

General ...............................................................................................................................................................27

Ergonomics .........................................................................................................................................................27

Environmental Technical Standards ....................................................................................................................28

How Many? .........................................................................................................................................................29

What Type? .........................................................................................................................................................30Fire Radio Features .............................................................................................................................................30

Portable Radio User Guide ..................................................................................................................................32

Accessories ..........................................................................................................................................................33

Summary ............................................................................................................................................................33


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Voic Raio Couicaios gui for h Fir Srvic tabl of Cos

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SECTION 5 TRUNKED RADIO SYSTEMS ............................................................................................................34

General Radio Operation ....................................................................................................................................35

Other Trunking System Features .........................................................................................................................37

Designing a Trunked Radio System .....................................................................................................................38

Summary ............................................................................................................................................................43

SECTION 6 SYSTEM DESIGN AND IMPLEMENTATION ................................................................................... 44

Project Organization ...........................................................................................................................................44

Requirements Denition.....................................................................................................................................45

Evaluation o Current System ..............................................................................................................................49

Should You Hire a Consultant?............................................................................................................................51

Where to Get Advice ...........................................................................................................................................51

Funding ..............................................................................................................................................................52

Procurement .......................................................................................................................................................53Implementation ..................................................................................................................................................55

Training and Transition ......................................................................................................................................55

Lessons Learned and Feedback ............................................................................................................................56

Operation and Maintenance ...............................................................................................................................56

Summary ............................................................................................................................................................57

SECTION 7 INTEROPERABILITY ........................................................................................................................58

Day-to-Day ..........................................................................................................................................................58

Large Incidents....................................................................................................................................................59Summary ............................................................................................................................................................61

SECTION 8 RADIO SPECTRUM LICENSING AND THE FEDERAL

COMMUNICATIONS COMMISSION ...............................................................................................................62

Rulemaking ........................................................................................................................................................62

Licensing ............................................................................................................................................................63

Federal Communications Commission Actions to Increase Public Saety Spectrum............................................63

Summary ............................................................................................................................................................69

SUMMARY ...............................................................................................................................................................70ENDNOTES ..............................................................................................................................................................71


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SECTION 1INTRODUCTION

PurposThe past ew decades have seen major advancements in the communications industry. Portable communicationsdevices have gone rom being used mainly in public saety and business applications to a situation where theyare in every home and in the hands o almost every American man, woman, and child. As users are added,there is more stress on the system; there is only so much room on the radio spectrum. The communicationsindustry and the government have responded by making changes to the system that mandate additionaleciency.

These advancements have improved radio requency spectrum eciency, but also have added complexityto the expansion o existing systems and the design o new systems. Some o these advances in technologyare mandated by the Federal Communications Commission (FCC), while others are optional. The costs andoperational eects o these changes are signicant. Navigating through the complex technological and legaloptions o public saety communications today led to the development o this guide to assist the re servicein the decisionmaking process.

why h Fir Srvic is diffrThe lie saety o both reghters and citizens depends on reliable, unctional communication tools thatwork in the harshest and most hostile o environments. Fireghters operate in extreme environments that

are markedly dierent rom those o any other radio users. Fireghters operate lying on the foor; in zerovisibility, high heat, high moisture, and wearing sel-contained breathing apparatus (SCBA) acepieces thatdistort the voice. They are challenged urther by bulky saety equipment, particularly gloves, that eliminatethe manual dexterity required to operate portable radio controls. Fireghters operate inside structures ovarying sizes and construction types. The size and construction type o the building have a direct impacton the ability o a radio wave to penetrate the structure. All o these actors must be considered in order tocommunicate in a sae and eective manner on the reground.

Radio system manuacturers have designed and developed radio systems that meet the needs o the majorityo users in the marketplace. The re service is a small part o the public saety communications market andan even smaller part o the overall communications market. This has resulted in one-size-ts-all publicsaety radio systems that do not always meet the needs o the re service as a whole or those o a specic

department. For a number o reasons, the re service is unique among public saety and other municipalcommunications users. A large percentage o radio communications by most municipal or government usersis done rom vehicle-mounted mobile radios. Public saety radio users, law enorcement, and the re service,use vehicle-mounted and portable radios. For much o the portable radio work by law enorcement personnel,the ocer is outside on the street, in an upright position, with good visibility. The ocer occasionally willgo inside a building and communicate. This is in sharp contrast to the environments that reghters ace ona daily basis.


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Voic Raio Couicaios gui for h Fir Srvic Section 1 Introduction

In many instances, radio systems perorm better or law enorcement than or the re service. The mainreason or this is that law enorcement operates dierently than the re service. In the law enorcementoperating model, the ocers are in a deployed state outside patrolling the streets. When an incident occurs,the dispatch center noties the patrol ocers o an incident, and an ocer or ocers respond to the call.Once ocers arrive onscene they may be operating as a single resource and only require communicationwith the dispatcher; at other times they may be operating with multiple responders, but the dispatcher

remains the ocal point o communications. Ocers in these situations are wearing standard patrol attireand have good visibility.

The re service operates in a staged state with resources located in re stations. Calls are dispatched to specicunits based on their location in relation to the incident. When more than one unit responds to an incident,an onscene Command structure is established to coordinate re attack, provide saety and accountability,and manage resources. The units assigned to these incidents work or the local Incident Commander (IC),who is the ocal point o communications on the reground. The dispatch center assumes a support role andsimultaneously documents specic reground events, handles requests or additional resources, and mayrecord reground tactical radio trac.

When comparing law enorcement to the re service and other public saety some major dierences areapparent.

Fir Srvic La eforc

Majority of incidents in buildings Majority of incidents on street

Contaminated breathing atmosphere requiring SCBA Safe breathing atmosphere

Often operate in a prone position Upright position

High temperatures Normal temperatures

Poor voice quality to radio Good voice quality to radio

High background noise on incident scenes Normal to high background noise

Poor to zero visibility Good visibility

Poor to no manual dexterity Good manual dexterity

Local Command structure coordination

Localized communications

Dispatch center coordination

Wide area communications


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SECTION 2BASIC RADIO COMMUNICATION TECHNOLOGY

When talking about re department communications systems usually we are talking about what aretraditionally called land mobile radio systems.

It is important or reghters and re ocers to have a basic knowledge o radio system technologies to helpthem during the design, procurement, or use o the radio system. By having this basic understanding, you willbe able to participate eectively in critical discussions with technical sta, consultants, and manuacturersto get the saest, most eective voice communications system or your reghters, Command Sta, andcommunity.

Most radio system users do not need a detailed understanding o the technology behind the systems they use.However, such knowledge is important or those involved in procuring the systems, in developing proceduresor the use o the systems, and in training eld users to have a more comprehensive understanding otheir operation. All technologies have strengths and weaknesses, and understanding those characteristics isimportant in making decisions related to the technologies. No matter what a salesperson will tell you duringthe procurement process, no system is without risk and all have had users who were not satised with someaspect o the system. The key is in understanding the technology enough to ask questions, understand theanswers, and make a successul evaluation.

Raio SpcruRadio communications are possible because o electromagnetic waves. There are many types o electromagneticwaves, such as heat, light, and radio energy waves. The dierence between these types o waves is theirrequency and their wavelength. The requency o the wave is its rate o oscillation. One oscillation cycle persecond is called one hertz (Hz). The types o electromagnetic energy can be described by a diagram showingthe types as the requency o the waves increase.

Fiur 1 th elcroaic Spcru.

1MHz

1km1000m

100m 10m 1m 10cm 1cm1mm

1000m100m 10m

1m1000nm

100nm

10MHz

100MHz

10MHz

100MHz

200MHz

300MHz

400MHz

500MHz

600MHz

700MHz

700MHz

800MHz

800MHz

900MHz

1000MHz

1000MHz

10GHz

100GHz

Frequency Increases

1000GHz

10THz

100THz

1000THz

Wavelength Decreases

AM Radio FM Radio / TV Wireless LAN Radar / MicowaveInfaRed

VisibleLight

UltraViolet

UHFVHFHigh

VHFLow


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Voic Raio Couicaios gui for h Fir Srvic Section 2 Basic Radio Communication Technology

When describing the requencies used by common radio systems, we use the metric system to quantiy themagnitude o the requency. A typical requency used in re department radio systems is 154,280,000,000Hz. This is a requency designated by the FCC as a mutual-aid radio channel. Dividing the requency by themetric system prex mega, equal to 1,000,000, this becomes 154.280 megahertz or MHz.

Land mobile radio systems are allowed to operate in portions o the radio spectrum under rules prescribed

by the FCC. These portions o the spectrum are called bands, and land mobile radio systems typically operatewith requencies in the 30 MHz (VHF low), 150 MHz (VHF high), 450 MHz (UHF), 700 MHz, and 800 MHzbands.

The wavelength is the distance between two crests o the wave. The requency and wavelength are inverselyrelated so that, as the requency o the wave increases, the wavelength decreases. The length o a radioantenna is related to the wavelength with which the antenna is designed to operate. In general, the higherthe requency o the waves used by the radio, the shorter the antenna on the radio.

Fiur 2 elcroaic wav.

Wavelength

Amplitude


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Channel BandwidthThe radio spectrum is divided into channels. Each radio channel is designated by a requency number thatdesignates the center o the channel, with hal o the bandwidth located on each side o the center.

Radio channel bandwidth is the amount o radio spectrum used by the signal transmitted by a radio. Thegreater the bandwidth, the more inormation can be carried by the signal in the channel. Minimum channel

bandwidth typically is limited by the state o technology, and the bandwidth required to carry a givenamount o inormation has decreased by several times over the past 50 years. However, there is a theoreticallimit below which the bandwidth cannot be decreased. In addition, the actual width o a channel oten isslightly greater than the minimum width, to provide some space on each side o the signal or intererenceprotection rom adjacent channels. For the purposes o radio licensing, the FCC sets the maximum andminimum bandwidth or channels in each requency band.

The bandwidth o channels typically used in land mobile radio is measured in thousands o hertz, orkilohertz, abbreviated kHz. In an eort to place more communications activity within a limited radiospectrum, permitted bandwidth has been decreasing. Under older licensing rules, some o which are still ineect, typical channel bandwidths were 25 kHz. Newer rules require bandwidths o 12.5 kHz.

Figure 3 Channel Bandwidth.

Raio wav PropaaioTo send a radio signal rom a transmitter to a receiver, the transmitter generates electromagnetic energyand sends that energy through a transmission line to an antenna. The antenna converts the energy into

electromagnetic radio waves that travel at the speed o light outward rom the antenna. I another antennais located in the path o the waves, it can convert the waves back into energy and send that energy througha transmission line to a receiver.

150.815

150.8225

150.830

150.8375

150.845

150.8525

150.860

150.8675

150.875

150.8825

150.890

150.8975

150.905

Existing 25 kHz bandwidth channels spaced at 30 kHZ intervals

Existing 25 kHz bandwidth channels spaced 15 kHZ from the original channels

New 12.5 kHz bandwidth channels at 7.5 kHZ spacing from existing channels

.

.

.


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Fiur 4 elcroaic Sial Raiaio.

Radio signals emitted rom an antenna travel both a direct path to the receiving antenna, and a path refectedrom the ground or other obstacles. This refection causes the wave to travel a longer distance than the directwave, as shown in Figure 5.

Fiur 5 Sial Pahs.

TRANSMITTINGSTATION

RECEIVINGSTATION

TRANSMISSIONLINE

INSULATOR INSULATOR

TRANSMISSIONLINE

STATION(EARTH)

ANTENNA(TRANSMIT)

ANTENNA(RECIEVE)

AIR(MEDIUM)

TRANSMITTING

ANTENNA

RECEIVINGANTENNA

DIRECT PATH

REFLECTED PATH


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IrfrcRadio requency intererence can be either natural or manmade. Intererence rom internal noise occursnaturally in all electronic equipment due to the nature o the electronic circuit itsel. Manuacturers takethis into account during equipment design, and obtaining a low-noise design is not particularly dicult.In addition, natural noise is produced by sunspot activity, cosmic activity, and lightning storms. This noise

usually is o small magnitude and not signicant or most land mobile radio communications. However,the VHF low band is aected signicantly by severe sunspot activity, sometimes to the point o completelyprohibiting communications.

More signicant to radio communications systems is the intererence produced by manmade sources.Vehicle ignitions, electric motors, high-voltage transmission lines, computers, and other equipment withmicroprocessors also emit radio signals that can interere with public saety radios.

In general, manmade intererence decreases with an increase in requency. The UHF band and, initially,the 800 MHz band are much less susceptible to manmade intererence than the VHF low and high bands.When systems are not subject to signicant intererence, they are said to be noise limited, in contrast tointererence limited. The large number o transmitters used by cellular telephone companies has createdintense intererence in the 800 MHz band.

Although the separation o the channels allocated to cellular companies has reduced this intererence,communications problems still can occur when a user is operating close to a cellular transmission acility.This type o intererence is particularly a problem when the user is located near a cellular acility and theusers radio system site is located much urther away. This creates a situation called near-ar intererence. Theusers system signal strength is low, and the cellular signal is high, keeping the users radio rom receivingthe desired signal. The 800 MHz band always was regarded as the cleanest band with respect to manmadeintererence, and systems initially were noise limited. However all systems in the band now must be designedor maximum intererence rom nearbytransmitters, requiring more transmitterlocations and higher power creatingmore costly systems.

Intererence rom cellular transmitters isillustrated in Figure 7. The blue area inthe center is the public saety transmitterand in the center o the grey areas arethe cellular transmitters.

Intermodulation intererence is causeddirectly by the mixing o two or moreradio signals. The mixing most commonlyoccurs inside the receiver or transmittero a radio. This mixing can create a thirdsignal that is radiated rom the antenna

out to other radios. The mixing also canoccur outside a radio in the transmissionline or through rusty tower bolts or guywires. Intermodulation can be dicultto identiy, due to the large number orequencies that may be present at largecommunications sites.

Fiur 7 gray Aras ar nar Far Irfrc Hols.


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Receiver desensitization intererence, also called receiver overload, is caused by nearby high-level transmittersignals that overload the initial parts o the radios receiver. This overload prevents the receiver rom detectingthe weaker desired signals, making the receiver nonunctional. Receiver desensitization occurs near high-power radio sites, such as television and radio stations, and also can occur in poorly designed repeatersystems where the transmit and receive requencies are too close in requency.

Several things can be done to reduce or eliminate intererence. The rst is the use o high-quality radioequipment. High-quality equipment has better transmitter and receiver perormance that minimizesintererence and reduces its eects. The use o receiver multicouplers, transmitter combiners, and repeaterduplexers reduces the possibility o intermodulation and receiver overload by ltering the transmitter andreceiver signals to ensure only those signals actually used by the system are passed through.

Radio system designers can reduce the possibility o their systems causing intererence by selectingappropriate designs. By selecting the appropriate antenna and adjusting transmitter power levels, the systemcan minimize intererence with other users o the same requency. This allows more ecient use o theavailable radio spectrum and keeps more resources available or all users.

wha Affcs Sys Covra?

The coverage o a radio communications system generally is described as the useul area where the systemcan be used reliably. Many actors aect coverage, including the radio power output, antenna height andtype, and transmission line losses. However, the actor that most infuences coverage is the height o theantenna above the surrounding ground and structures. By locating the antenna on a tower or mountain top,the system designer provides a more direct path rom the transmitter to the receiver. In the case o one radiouser transmitting directly to another radio user, having the radio antenna as high as easible (hand held atshoulder height) signicantly improves coverage.

Antennas have three major properties: operating requency, polarization, and radiation pattern. In general,these properties apply whether the antenna is used or transmitting or receiving. The operating requencyo an antenna is the requency at which the antenna acts as specied by its manuacturer. The antenna mayoperate outside its design requency, but the perormance o the antenna will be reduced.

In land mobile radio systems like those used by public saety, most antennas are vertically polarized. Youcan see evidence o this with the wire antennas mounted on the roos o vehicles. Like car antennas designedor requency modulation (FM) broadcast radio, they stick up vertically rom the surace o the vehicle.

The radiation pattern o the antenna is the shape o the relative strength o the electromagnetic signalemitted by the antenna, and this depends on the shape o the antenna. The radiation pattern can be adjustedthrough antenna selection to provide coverage where desired and to minimize coverage (and, in turn,intererence) in undesired directions.

Fix-Si Aas

Fixed-site antennas are mounted on towers or buildings to provide the dispatch orrepeater coverage throughout the service area. The antennas used must be designed

to operate in the systems requency band and, or best power coupling, shouldhave a center requency as close as possible to the actual operating requency.

The radiation pattern or the antenna should be selected to provide a signal in thedesired sections o the coverage area, and have minimal coverage outside the desiredcoverage area. This will help ensure that the system is not interering with othersystems unnecessarily. The most basic practical antennas are omni-directional, andhave approximately equal coverage or 360 degrees around the antenna.

Fiur 8 Aa

tor a Aas.


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However, as shown in Figure 9, the antenna pattern is morelike a slightly fattened donut. This causes an area immediatelyunder the antenna to have lower signal strength, and lesscoverage, than arther away rom the antenna.

Directional antennas are used to direct the signal toward the

users and away rom unwanted areas. The antenna is said tohave gain over an omnidirectional antenna in the direction ohighest signal. Figure 10 shows a directional antenna calleda Yagi, along with its radiation pattern looking down on theantenna. The pattern shows a stronger signal rom the ronto the antenna and a weaker signal rom the back. The signalstrength protrusions behind the main signal are called lobesand, in most cases, antenna designers strive to minimize thisunintended signal.

Fiur 9 Oiircioal Aa

Par.

Fiur 10 dircioal Aa a Par.

When an antenna is located on top o a mountain or tall building, the coverage loss created by the hole inthe radiation donut may have a signicant impact on coverage in the area immediately around the antenna. Tocompensate or this, a directional antenna can be tilted slightly to direct more o the signal downward, asshown in Figure 11. This tilting is known as mechanical down-tilt and increases the energy immediatelybelow the antenna while reducing the maximum distance the signal will travel. Unortunately, when usingan omni-directional antenna, tilting the antenna down in one direction results in tilting the pattern up onthe opposite side o the antenna. For this reason, special antennas with electrical down-tilt are used whenomnidirectional coverage is required, such as on a tall building in the center o the coverage area.

Fiur 11 do til.


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mobil a Porabl Aas

In general, all mobile and portable radio antennas areomnidirectional to provide coverage 360 degrees around the radiouser.

Vehicle antennas should be mounted so that they are not obstructed

by equipment mounted on the top o the vehicle. Light bars, airconditioning units, and master-stream appliances are some typicalobstructions ound on re service vehicles. Some obstructions,such as aerial ladders on truck companies, cannot be avoided, andthe designer must select the best compromise location.

Vehicle antennas mounted on the roo o re apparatus canbe damaged by overhead doors, trees, and other obstructions.Ruggedized low-prole antennas oten are a better choice, eveni they have a lower gain than a normal whip antenna. A properlymounted intact antenna with a lower gain is much better than adamaged antenna o any type.

Portable antennas usually are provided by the portable radiomanuacturer and are matched to the radio. In some cases alternativeantennas can be selected or the radio to overcome specic userconditions.

When a portable radio is worn at waist level, such as with a belt clipor holster, the users body absorbs some o the signal transmitted orreceived by the radio. In addition, the antenna is at a much lowerlevel than i the user were holding the radio to his or her ace ortransmitting.

Since the radio system is designed or use with the antenna oriented vertically, the perormance o the radiois reduced when the antenna is horizontal. This is particularly important or reghters, since the radio theyuse may become oriented horizontally when they are crawling low inside a structure re.

0.000.100.200.300.400.500.600.700.80

0.901.001.101.201.301.401.501.601.701.801.902.002.102.202.302.402.502.602.702.802.903.003.103.20

Flex Whip

at Head Level

Hip Level

Flex Whip

with Swivel Case

Hip Level

Flex Whip

with Belt Clip

Portable Radio Antenna Performance

Fiur 12 Rlaiv Sial Lvls.

Fiur 13 Raio Aa Plac.


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SuaryRadio communication takes place using electromagnetic waves that travel rom the transmitter to the receiver.These waves can be refected or absorbed by materials such as buildings, the earth, or trees, reducing thestrength o the wave when it reaches the receiving antenna. Elevating the transmitting or receiving antennawill reduce the likelihood o the wave being aected by buildings or trees, because the path to the receiver

will be more direct.Intererence rom undesired radio waves is always a possibility in a radio system. The potential or naturalintererence decreases as the requency band increases, but manmade intererence is very high in the 800MHz band due to the proximity o cellular and other non-public saety communications systems. Thisintererence can make it dicult to communicate eectively in the presence o the intererence.

When designing radio communications systems, the designers must take into account the presence orefecting or absorbing materials and intererence. This may require constructing taller towers to support theantennas or increasing the power o the transmitters to overcome the loss o signal strength and intererence.The system design must take into account local terrain, trees, buildings, and the density o intererence-generating sources.


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SECTION 3RADIOS AND RADIO SYSTEMS

Several dierent types o radios are used in the re service. These radios can be classied as mobile, portable,or xed; analog or digital; and direct, repeated, or trunked radios. In this section we discuss the operation othese types o radios, and the eatures, benets, and problems associated with their use in the re service.

Mobile radios are designed to be mounted in vehicles and get their power rom the vehicles electricalsystem. They can be o either a one- or two-piece design, with the radio itsel separated rom the controls.An external antenna is connected to the radio and permanently mounted to the vehicle. Mobile radios usually

have better perormance than portable radios, including better receivers and more powerul transmitters.Mobile radios used in trunked radio systems may or may not have more powerul transmitters because thesystems are designed or portable use, reducing the need or high-powered transmitters.

Portable radios are hand-held radios powered by rechargeable or replaceable battery packs. They usually havean external rubber antenna attached to the top o the radio.

Mobile and portable radios have similar controls to perorm their essential unctions. These include thingssuch as changing channels, adjusting the speaker volume, and transmitting. The common names or thesecontrols are the channel (or talkgroup) selector, volume adjustment, and push-to-talk (PTT) switch. Someradios, particularly those intended or re and police use, will have an orange or red EMERGENCY button.This button may be programmed to indicate to the radio system, and to other users, that a user has anemergency. Older radios may have a squelch adjustment knob, but most modern radios have internal control

settings or adaptive squelch so that a squelch adjustment knob is no longer necessary.

Base station radios are located at xed locations, and usually are powered by AC utility power. Base stationsgenerally are higher in perormance than mobile and portable radios, with higher-powered and more stabletransmitters and more sensitive and intererence-resistant receivers. Some re departments equip re stationswith base station radios to provide enhanced coverage throughout their service area and to provide backupcommunications in the event o a primary communications system ailure.

Repeaters are similar to base stations, but they can transmit and receive at the same time, retransmitting thesignal received by the receiver. Repeaters are used to extend the coverage o portable or mobile radios.

Radio console equipment is used by dispatchers to control base station radios and repeaters and allowthe dispatcher to receive and transmit on one or more radios simultaneously. The consoles typically have

individual volume and transmit controls or each radio as well as a master volume and transmit control.Headsets can be connected to the consoles along with ootswitches, allowing dispatchers to operate theconsole hands-ree so they can operate computer equipment simultaneously.


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Voic Raio Couicaios gui for h Fir Srvic Section 3 Radios and Radio Systems

Aalo RaiosThe human voice is an analog signal; it is continuously varying in requency and level. Analog radios havebeen in use since the invention o voice radio in the early 1900s. The type o analog radio used today wasinvented in the 1930s to improve on the older radios poor immunity to noise. These radio systems userequency modulation (FM) to modulate the transmitted signal with the users voice. The main advantage o

FM over older radio system types is that FM radios tend to reject (interering) signals that are weaker thanthe desired signal.

Analog FM radios operate by causing the transmitting requency o the radio to change directly with themicrophone audio. Initially the signal is ltered to remove any requencies above human voice, but no otherchanges are made to the signal. Figure 14(A) shows an example signal rom the microphone, and Figure14(B) shows the resulting change in requency o the transmitted signal.

FM radios constantly have a signal at the output o the receiver, and a squelch circuit is used to mute theoutput o the radio receiver when no desirable signal is present. Noise squelch circuits mute the output aslong as only squelch noise is present. Most older radios eature adjustable squelch level controls, allowingthe user to make the radio less sensitive i there is intererence. However, most new radios have improvedreceiver perormance and have xed squelch levels or levels that are adjustable only by radio technicians.

To urther reduce received noise and intererence, well-designed analog radio systems use tone-coded squelch(TCS) or digital coded squelch. TCS is also known by its Motorola trademark Private Line or PL and by itsGE (now M/A-COM) trademark Channel Guard.

TCS systems mix a subaudible tone with the audio rom the microphone and transmit the resulting signal.When a radio receives a signal with tone-coded squelch, the TCS decoder attempts to match the tone presentin the received signal with the desired tone. I the correct tone is present, the receiver is unsquelched andaudio is routed to the speaker.

Fiur 14 Frqucy moulaio.


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diial RaiosTo improve audio quality and spectrum eciency, radio manuacturers introduced digital radios. This wasa necessary move based on the FCC requirements to continue narrow banding. Since being introduced,digital modulation has been touted as having more user eatures, better audio clarity, and higher spectrumeciency than analog modulation.

In the digital world when a user speaks into the microphone the radio samples the speech and assigns thesample a digital value. A vocoder (voice coder) or codec (coder/decoder) in the radio perorms the unctiono converting analog voice to a digital data packet. The digital data packet can vary in the number o bits.The higher number o bits in the data packet, the higher the level o precision. Numerous samples are takeneach second to reproduce the source audio. The higher sample rate per second and number o bits per sampleresult in increased audio quality. For example, compact disc (CD)-quality audio samples 44,100 times persecond and the number o graduations in the sample is 65,536. The use o digital audio was expected toreduce static and increase the range o radios in weak signal conditions.

Specication Cd Auio dVd Auio Saar Public Safy diial (P25) Auio

Sapli Ra 44.1 kHz 192 kHz 50 Hz

Sapls Pr Sco 44,100 192,000 50

diial Auio Procssi

A vocoder in a digital radio converts analog voice to a digital interpretation rom an audio sample. Digitalradios, unlike CD or DVD audio, have very limited data rates. Even cell phones have higher data rates thana digital radio. Because o limited data rates, digital radio audio is sampled at a much lower rate with lessprecision. Designers o the portable radio vocoders elt the radios did not need the same level o precision asCD-quality audio, since reproduction o human speech was the goal.

This is a basic explanation o how analog voice is processed by the radio.

Transmitting radio:

1. The user speaks into microphone.

2. The audio is sampled and converted to a digital interpretation by an analog to digital converter (A/Dconverter).

3. The vocoder converts the digitized speech into digital data.

4. The modulator modulates the radio requency (RF) with the digital data.

5. The modulated RF signal is boosted in power by transmitter amplier.

6. The signal is transmitted rom the radio antenna.

Receiving radio:

1. The modulated RF is received by antenna.

2. The received RF signal is boosted to a useable level by the receive amplier.

3. The signal is demodulated by a demodulator. This removes the RF component o the signal leaving thedigital data component.

4. Digital data is decoded by the vocoder into digitized speech.

5. Speech data is converted to an analog signal by a digital to analog converter (D/A converter).

6. Analog is sent to the speaker.


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Aalo vrsus diial Sial Variaios wih Sial Srh

As the radio user travels urther rom the transmitting radio, the signal strength decreases. The signal strength

directly aects the ability o the radio to reproduce intelligible audio.In an analog system, the clarity and intelligibility o the transmission, as received by the user, decreasedirectly as the signal level decreases. The noise (static) in the signal progressively increases in strength, whilethe desired signal decreases, until the transmitting user cannot be heard over the noise.

When a digital user transmits to a receiver, the transmitted signal decreases just as the analog signal does.However, the error correction in the digital transmission contains extra inormation that allows the audioinormation to be heard even with a large decrease in signal level. As the receiver travels urther rom thetransmitter, the signal level decreases to the point where the error correction cannot correct all errors inthe signal. When this point is reached, the receiving users will hear some distortion in the signal and mayhear some strange nonspeech noises. These strange nonspeech noises are sometimes called Ewoking aterthe language spoken by the Ewok characters in the movie Star Wars.1 Once this point is reached, a small

reduction in signal level will cause the number o errors to exceed the ability o the system to compensate,and all audio will be lost.

The problem this causes is that the radio signal goesrom usable to unusable with little or no indicationthat this is about to occur. Figure 16 shows that,with an analog radio system, the signal slowlygets noisier, giving the user hints that the signal isgetting weaker. This behavior adds to the situationalawareness o the user and allows him/her to makedecisions about the environment. Although digitalradios provide a larger range o usable signal

levels, the lack o advance indication o signal leveldecrease allows users to get closer to complete losso communication without any advance warning.Some radio manuacturers have indicated theywould develop solutions to this problem; howeverthere are no solutions implemented in currentproduction radios.

Fiur 15 diial Raio.

100

1

2

3

4

5

20Distance

Miles

Analog

Signal

Understandability

30 40

Digital

Signal

Fiur 16 Aalo vrsus diial Sial.


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APCO P25The Association o Public Saety Communications Ocers (APCO), representing the public saety technicalcommunity and the Telecommunications Industry Association (TIA), recognized there would be arequirement to move to digital technology. This provided an opportunity to develop an open standardthat would allow dierent manuacturers to build equipment that could operate together. The goal was to

introduce competition into the market, help control costs, and provide a technology platorm or improvedinteroperability.

Up until the development o this standard, each manuacturer had proprietary digital radios that couldinteroperate only with like radios. Working with the TIA, APCO coordinated the work o manuacturersto develop the P25 Standard or digital radios. Modern public saety digital radios use this standard. P25is the national standard or public saety digital radios, but also is backward compatible or analog use.This standard was developed to allow radios rom multiple manuacturers to communicate directly usinga common digital language, dene standards or trunked radio systems to allow multiple manuacturers tooperate on a common platorm, and to provide a roadmap or uture eatures and capabilities.

wha P25 is no

P25 does not address any operational or interoperability needs. P25 does not provide a re department withinteroperability unless it is planned or. A lone agency on P25 is no more interoperable than being on a UHFsystem trying to interoperate with a department on VHF. P25 only provides manuacturers with a commondigital language or the radios and system inrastructures.

P25 system standards also were meant to allow radios o dierent manuacturers to operate on any otherP25-trunked radio system. This has not been the case to date. System manuacturers were allowed to developproprietary eatures within the P25 standard. This has resulted in an open architecture that isnt as openas intended. This is especially true in large, complex multizone trunked systems, where complex proprietaryroaming schemes are used to allow radios to operate over large geographic areas.

P25 Characrisics i Hih-nois eviros

When P25 is used in settings where the background noise level is within limits set in the P25 standard, itprovides useable audio. However the P25 vocoder was not designed to operate in the high-background-noiseenvironments encountered on the reground. When the P25 vocoder was being developed, the designerstested intelligibility o the digital audio with high ambient noise levels at the receiving radio. The P25 vocoderis unable to dierentiate the spoken voice rom the high background noise and assigns a digital value thatdoes not accurately represent the voice. The result is unintelligible audio or broken audio with digitizednoise artiact. Users o P25 radios have been aected by many common reground noises. The SCBA andalerting systems or low-air or inactivity and PASS (Personal Alert Saety System) devices have made the audiotransmitted rom digital radios unusable. P25 radios transmitting rom high-noise environments do notperorm to the same levels as analog radios.

Self-Contained Breathing Apparatus Mask Effect on CommunicationsThe eect o SCBA masks on the human voice has been studied by the Institute o Electrical and ElectronicsEngineers (IEEE).2

The IEEE tests were perormed to nd the eects o the SCBA system on voice intelligibility. Tests wereperormed with no SCBA mask and with an SCBA mask, with analog audio and digital audio. Participantswearing the SCBA masks read standard word recognition sentences while the listeners recorded what theythought they heard. As you will note in the table below, digital word error rates (WER) were always higherthan analog error rates. Digital in Mask A had an average WER o 12.5 percent and digital in Mask B had an


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average WER o 6.8 percent. All o these tests were perormed in a sound studio with no background noise.In an actual reghting situation, the WER likely would be higher. Tests were also perormed with the SCBAlow-air alarm rom each manuacturer in operation. In these tests the WER averaged 18.7 percent in analogand increased to 64.4 percent in digital.

Speaker No mask

Aalo weR%

No mask

diial weR%

Mask A

Aalo weR%

Mask A

diial weR%

Mask B

Aalo weR%

Mask B

diial weR%

Male 1 1.3 1.8 5.3 12.0 5.5 6.1

Female 1 2.7 3.5 4.8 11.4 3.7 6.9

Male 2 1.6 3.1 4.2 14.2 4.2 7.3

Avra 1.9 2.8 4.8 12.5 4.5 6.8

P25 Digital for Fireghting?

Fire departments around the country have reported diculties with digital radios, and studies perormed

by National Institutes o Standards and Testing (NIST), the International Association o Fire Chies (IAFC),and portable radio manuacturers have supported the ndings rom the eld users. Based on the experienceso re departments using digital radios and the studies in response to these problems, the InternationalAssociation o Fire Fighters (IAFF) has taken a position that does not recommend P25 digital portable radiosor re-ghting applications where the reghter is using an SCBA.

These studies cite decreases in the ability o the reghters voice to be translated into a digital signal bythe P25 radios. When reground noise is introduced, the voice translation ability o the P25 radio providesdecreased to no intelligibility. These problems are worsened when the reghter is speaking into the portableradio through an SCBA acepiece, with or without a microphone inside the acepiece. Bone microphones orthroat microphones may minimize the intererence caused by background noise but are impractical or mostreghting portable radio uses. Speaker microphones are subject to the same problems that are ound with

the microphone on the portable radio.The conguration o the P25 vocoder is limited in its capability to translate the human voice in the presence ocommon reground noise or through a acepiece. This can pose a saety hazard or reground operations. Tomaintain saety, re departments should consider using portable radios that incorporate analog modulation

or operations where the reghter is using an SCBA.

Radios using the P25 digital technology have perormed well or other re service unctions, such as onemergency medical incidents, support unctions on the reground where an SCBA is not required, andlaw enorcement operations. The diculties presented by the inability o P25 radios to produce intelligiblevoice messages in the presence o reground noise is a signicant saety concern and should be consideredseriously by public saety radio system designers and users.

The communications industry is aware o the present operational problems with P25 vocoders. I this issueis addressed and corrected by the industry, uture P25 radios may be suitable or reghting operations.Another area o opportunity or improvement is or the portable radio unction to be more completelyintegrated into the SCBA. This integration may lessen the impact o background noise on the vocoder.


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dirc a Rpa Raio SyssRadios communicate when the transmitter sends out a signal that is received by one or more receivingradios. When the signal is received rom the radio initially transmitting the signal, the communication isdirect (i.e., there is no intervening radio or system). One radio transmits, the other radios receive, and thistype o communications also is known as simplex communication.

nosuppor Siplx Couicaios o h Firrou

Using simplex communications maintains positive communications between the IC, exterior onsceneunits, and interior units without the reliance on exterior communications systems. Maintaining positivecommunications is especially important in Mayday situations. When users on simplex radios are deployedto the interior o a structure they create a radio receiver network. As more and more radios move into thestructure, the strength o the network increases. I Engine 1 calls Mayday, the probability o another radio onthe interior receiving the transmission is high. I the Mayday is not heard by the IC, another radio operatoron the interior can act as a human repeater to repeat the message to the IC. In addition, the number o radiosin a structure creates redundancy, where reliance on a single repeater or trunked system creates a single pointo ailure. Simplex communications allow direct communications with the initiator o the Mayday and other

crews on the reground.In this example, the simplex communications are not supported. This means that there is no inrastructureto support transport o the reground communications to the dispatch center. When the radios involved indirect communication are portable radios, the communication distance typically is limited to a ew miles; ormobile radios the distance can be 50 to 100 miles. Oten this is reerred to as line-o-sight communicationand this makes direct radio communication most suitable or use by units on an incident scene.

Fiur 17 Siplx Firrou Couicaios.


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The direct communication method is the simplest orm o radio communication and is easily aectedby terrain blocking. I a mountain or other obstruction is between the transmitting and receiving radios,communication may not be possible. However, the short-range nature o direct communication also allowsthe radio channel used by one communicating group to be reused by another group urther away. I thesecond group is ar enough away that it does not hear the rst groups communications, then the channelcan be reused. This minimizes the number o channels needed by an agency.

When a radio system must cover a larger area, or when terrain or other obstructions limit the distance asystem can cover, additional equipment is needed to overcome these limitations.

Rcivr Vors Iprov Fil Ui o dispachr Couicaios

Dispatch centers connected to high-powered transmitters provide the dispatch center with talk-out capability.Transmitters are elevated to achieve better line-o-sight communications with the service area. High-poweredtransmitters ensure that the dispatch center transmissions are heard throughout the service area and providesome level o in-building coverage. See Figure 18.

Portable radios have limited power and cannot always transmit a signal strong enough to reach the transmittersites. To provide a more balanced system, receivers are networked together throughout the service area ina receiver voter system (RVS). Comparison o the received audio signal takes place in a receiver voter.The receiver voter and its network o receivers are reerred to as the RVS. The RVS usually is located at thedispatch center. The receiver voter compares the audio rom all receivers and routes the audio rom thereceiver with the best audio quality to the dispatcher. This type o system provides very reliable regroundcommunications and supports reground simplex channels.

Fiur 18 Siplx Firrou Couicaios ih dispach Cr.


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Rpars Iprov Fil Ui o dispach a Offsc Uis

Receiver voters are one solution to get communications rom a radio user to the dispatch center, but anothersolution is needed to get the communication to other radio users. One type o system that can solve thisproblem is a repeated radio system. Repeated radio communication, also known as hal duplex communication,uses two radio requencies or communication. The transmitting radio transmits on requency 1 (F1), andthat signal is received by the repeater. The repeater then repeats the transmission on requency 2 (F2), andthis signal is received by the receiving radio. By locating the repeater on a high building or mountain, therange o transmissions rom the transmitting radio can be more than doubled, and can reach over obstacleseectively.

Another solution to improving communication between eld units inside buildings or tunnels and dispatch

and oscene units is the bidirectional amplier (BDA). BDAs can be used with hal duplex radio systemsto extend coverage rom inside the structure to the outside o the structure and vice-versa, but BDAs donot operate with simplex radio systems. BDAs are discussed in more detail in Section 5Trunked RadioSystems.

Fiur 19 Siplx Couicaios ih Porabl trasii.


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Fiur 20 Half duplx Firrou Couicaios.

The signicant operational dierence between direct and repeated communications systems aects unitsoperating at an incident scene. With direct communication, the transmitting radios signal only needs toreach other radios directly on the incident scene. With a repeated system, the signal must reach the closestrepeater location, which may be much urther rom the incident than the receiving radios.

Figure 21 on the next page, shows a method to overcome this limitation. I unit E1 is unable to communicatewith other units on the reground using the repeater system, E1 can switch to talkaround mode on the radio.This mode allows the unit to transmit in direct mode to other radios on the reground and receive romthe units in either direct or repeated mode. Since the radio is not able to reach the repeater, the dispatchcenter cannot hear the radio, although other radios on the reground can hear the unit. A unit that switchesto talk-around should announce this immediately so other units know that they also may need to switch tocommunicate with the isolated unit.


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Figure 21 Half Duplex Communications with Talkaround.

Siulcas trasir Syss

When a radio system must cover a large area, but the number o available requencies is limited, a simulcasttransmitter system may be the solution. With this system, multiple transmitters simultaneously transmit onthe same requency. The transmitters must be precisely synchronized so that the signals they transmit do notinterere with each other. In addition, the audio source sent to the transmitters must be synchronized so thatthe radio user hears the same signal rom each transmitter. The system consists o a simulcast controller andtwo or more simulcast transmitters. The advantages o a simulcast system are the coverage o a large area,with high signal levels throughout the area, while using only a single requency.


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Fiur 22 Siulcas trasissio fro dispach Cr.

Opraioal CosiraiosCommunication needs on the reground can be categorized based on the position in the Command structure.The military operates in a similar manner and is used here to illustrate the concept.

In a military theatre o operations, there are distinct communication requirements based on position in theCommand structure. At the lowest level are individual team communications. This level o communication isor command and control o the team members to accomplish a task. Like the re service, these communicationsare oten simplex communications and short range. An example o this would be communications over aSCBA intercoma short-range, low-power radio designed or communications among a single company orcrew.


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Figure 23 SCBA Intercom.

Next is the tactical level, where the tactical Command element is communicating with multiple teams toaccomplish the tactical objective. This level requires communications with enough range to communicate withall teams assigned to achieve the tactical objective. The equivalent in the re service would be the regroundtactical radio channel or talkgroup where the IC is coordinating a re attack with several companies.

The last level is the strategic level, where a military commander is responsible or several areas o operation.This requires wide area communications to communicate with each tactical commander in his/her area ooperation. In the re service, the strategic-level communications commonly are wide-area communicationsto the dispatch center or requests or additional resources and documentation o tactical benchmarks. Thedispatch center has the strategic responsibility o maintaining response capabilities in the unaected areaso the city.

Additional communications layers should be considered based on the amount o radio trac occurring on aradio channel and the complexity o the operation, i radio channels or talkgroups are available. When radiochannel trac increases to the point that the channel becomes saturated, this, in itsel, becomes hazardous.I a Mayday or other emergency occurs there is no reserve capacity on the radio channel to handle theevent. Complex operations oten require immediate radio communications ree o other radio chatter, andshould be assigned a separate channel.


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Fireground communication systems should address the operational levels where communications areoccurring. A common practice is to assign responding units two radio channels when dispatched. Onechannel is designated a Command channel, and the second is the tactical channel. The Command channelprovides the IC with a wide area channel to communicate with the dispatch center. The tactical channel isa simplex channel or reground communications with crews assigned to interior re attack. This is a pureseparation o the tactical and strategic levels. Other departments oten mix the strategic and tactical levels by

having the dispatch center monitor and document tactical-level communications on a single channel.


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SECTION 4PORTABLE RADIO SELECTION AND USE

gralThe success o a re service radio system project hinges on the perormance o the portable radio. I theportable radio has poor perormance, the end-user relates it to the perormance o the radio system as awhole. All the reghter knows is that when the PTT was pressed the communications worked or did notwork.

Manuacturers oer radios at dierent price points to meet market need. As with any other product, the

options and perormance levels increase with the cost. Usually there are three tiers o radios available. At thelowest level are nonruggedized radios meant or users who do not handle radios in a rough manner and donot operate in environmental extremes. The second level o radio is or the user who needs more reliabilityand perormance eatures. The highest tier radios are ocused on the public saety user. They oer the highestlevels o perormance and reliability and have the most options available. At this level, the radios oten aresubmersible and have intrinsically sae options. Submersible radios are a very worthwhile option or the reservice, considering the possibility o radios getting wet or exposed to steam.

erooicsTodays radios are an integral part o reghting and a key component o reground saety. The orm and to the radios or reghting has not improved much over the past decade. Buttons and knobs have increased

in size as compared to the radios o the 80s and 90s, but reghters have the same diculties operatingradios while in personal protective equipment (PPE). Radio knobs still cannot be manipulated with a glovedhand, even though it is required as a component o National Fire Protection Association (NFPA) Standard1221, Standard or the Installation, Maintenance, and Use o Emergency Services Communications Systems.

9.3.6.6 Portable radios shall be designed to allow channels to be changedwhile emergency response personnel are wearing gloves.


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Voic Raio Couicaios gui for h Fir Srvic Section 4 Portable Radio Selection and Use

The radios o today can be programmed with hundreds o channels or talkgroups. The large number ochannels/talkgroups has made hard switches that correspond with a channel/talkgroup impossible. Toselect channels on radios with added channel capabilities requires liquid crystal displays (LCD) and sotkeys to provide access. In reghting, the LCDs are not readable in smoky environments and the sot keyscannot be pressed with a gloved hand. When programming the radio, take care to make reghting radiochannels easily accessible.

eviroal tchical SaarsRadios are designed to operate in environmental ranges. The harsh environment o reghting is hardon equipment and personnel. To provide reliable communications, it is common to purchase ruggedizedcommunications equipment. The technical specications and testing protocols used to determine i a deviceis rugged can be conusing. Manuacturers use several testing protocols to determine i the device is PublicSaety Grade. Some o the more common standards encountered are Military Standards (Mil Std) andInternational Electrotechnical Committee (IEC) standards.

IEC IP (Ingress Protection) Codes

IP codes are international standards that test or ingress protection into an electrical enclosure.

Manuacturers use this code to rate intrusion against solid objects rom hands to dust and water inelectrical enclosures. The rating consists o the letters IP ollowed by two digits. The standard is intendedto provide an objective testing protocol to reduce subjective statements such as waterproo. The rstdigit represents the size o the object that is protected against and the second digit represents the waterprotection. More detailed inormation on this standard can be ound at www.iec.ch, InternationalElectrotechnical Committee, IEC 60529.

Mil Standards

In the 70s and 80s radios were manuactured to various industry standards or ruggedness andtechnical stability. In the 90s radio manuacturers adopted Mil Std 810 as a standard or reliability andruggedness. Mil Std 810 was developed by the military to provide an environmental test protocol thatwould prove qualied equipment would survive in the eld. Mil Std 810 is a test protocol written or

the military environment not the reghting environment. The specication sheets oten reerence aletter designation behind the Mil Std. The letter designation represents the revision level o the Mil Stdbeing tested to. The latest revision is Mil Std 810 F. Earlier revisions o the Mil Std 810 were genericup to revision C. Subsequent revisions became more tailored to the actual environment the equipmentwould operate in. Manuacturers sometimes only perorm specic test components o the Mil Std. Forinstance, an equipment specication may read Mil Std 810 F or water, dust and shock resistance.When we see Mil Std 810 we assume that the equipment is ruggedized and will survive the reghtingenvironment. We need only look to the temperature specication to see that this is questionable. MilStd 810 F actually has two temperature specications depending on where the equipment is to beused.


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mil S 810 F Hih tpraur tabl.

dsi typ Locaio Abi Air C

(F)

Iuc 2 C

(F)

Basic Hot may pars of h orl, xi ouar fro ho

caory of h Ui Sas, mxico, Africa, Asia, a

Ausralia, souhr Africa, Souh Arica, souhr

Spai, a souhs Asia.

30 - 43

(86 - 110)

30 - 63

(86 - 145)

HoNorthern Africa, Middle East, Pakistan and India,

souhsr Ui Sas a orhr mxico.

32 - 49

(90 - 120)

33 - 71

(91 - 160)

The table shown is the high temperature table rom Mil Std 810F. A similar table is included in Mil Std 810 For low temperatures. Most manuacturers test to the Basic Hot and Basic Low temperature levels. Thistemperature range is rom approximately -30 C to 60 C (-22 F to 140 F). These temperature extremes donot replicate the environments that reghters encounter.

naioal Isiu of Saars a tcholoy tsi

NIST has perormed testing on portable radios that more closely mimics the reghting environment.4

The results o these tests exposed the vulnerability o the portable radios to elevated temperatureconditions, and emphasized the need to protect the radios when used in reghting situations. Radiostested inside the turnout gear pocket showed that the turnout gear pocket was able to protect the radiosand allow them to operate at the Thermal Class III temperature o 260 C. This contrasts with testswhere the radios were exposed directly to the airfow, in which the radios did not survive at ThermalClass II conditions and beyond. In all but one test, the exposed radios were able to operate properly atthe Thermal Class I temperature o 100 C, above the listed maximum operating temperature o 60 C.Failure o the electronics due to heating was not permanent or the radios. In all cases where the radiocasing was not damaged, the radios regained normal operating unction once they had sucientlycooled. Permanent damage to the casing, such as diculty turning knobs or pressing buttons did occuror some radios whose casings experienced melting. Permanent damage also occurred to the externalspeaker/microphones, especially due to the melting o the connecting cables.

The next step or this project is to work with the NFPA to develop a radio standard that would includerequirements or the thermal testing o handheld radios.

Ho may?Ater dening the technical and operational requirements o the radio, the number o radios needed has tobe determined. Departments have to identiy who needs radios. A portable radio or each reghter providesthe highest level o saety. In addition to reghters, radios or support and other re department unctionsshould be considered.

Additional guidance can be ound in the ollowing NFPA standards:

NFPA 1561, Standard on Emergency Services Incident Management System:

- 6.3 Emergency Trafc.

- 6.3.1* To enable responders to be notied o an emergency condition or situation when theyare assigned to an area designated as immediately dangerous to lie or health (IDLH), at least oneresponder on each crew or company shall be equipped with a portable radio and each responder onthe crew or company shall be equipped with either a portable radio or another means o electroniccommunication.


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NFPA 1221:

-9.3.6 Two-Way Portable Equipment.

- 9.3.6.1 All ERUs (Emergency Response Units) shall be equipped with a portable radio that is capable otwo-way communication with the communications center.

wha typ?Since radios are tiered based on perormance and ruggedness, there can be signicant cost savings by buyinghigh-tier radios or responders and the appropriate lower tiered radios or support sta.

High-tier High-tier radios should be provided to each reghter. This level o radio gives the highest

level o perormance and reliability that radio manuacturers can provide. Within each tier there may beoptions that provide additional capabilities or unctions. I using radios or emergency medical services(EMS) and re unctions, encryption may be required or operations with law enorcement agencies or tocomply with the Health Insurance Portability and Accountability Act o 1996 (HIPAA) requirements.

Midtier Midtier radios may be appropriate or users who do not enter into the reghting environment.This type o radio would be a good choice or EMS unctions. Again encryption may be required to meetHIPAA requirements.

Low-tier Low-tier radios are an option or some support sta. These radios provide communicationsor users who are not in harsh environments and may not need all the unctionality o the higher tieredradios.

Fir Raio FaursMany eatures are available in modern radios. Like automobiles, stripped-down versions o radios areavailable, but when options are added the cost rises. To identiy the desired eatures, ocus and user groupscan assist in developing the radio eature sets that meet users needs. Todays radios are extremely fexible inprogramming eatures and the unctions o buttons on the radio. Cooperation between the radio vendor andtechnical provider or your radio system will be instrumental in ltering through all o the programmingparameters. Some o the newer eatures that increase reghter saety are

Hih-ir Raios miir Raios Lo-ir Raios


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Voice channel announcement This eature uses prerecorded voice prompts to notiy the reghter whatchannel the radio is on as the channel select knob is moved.

Emergency indications Radios on the reground receive an indication o emergency activations on theassigned channel.

Personnel accountability In new systems there are more radio ID numbers available. This makes it

possible or each radio to have an individual ID code enabling identication o the unit and specicposition o the unit on an emergency activation. I tied to roster inormation in a computer-aided dispatch(CAD) system, identication o the individual reghter is possible.

Tones Many radios use tones as an indication o trunked system access, out o range, repeater access,encrypted channel, and others. Use o tones may provide added awareness to the reghter and, thus,increase saety.

For guidance on the minimum eature set a radio should have, reer to NFPA 1221 Section 9.3.6:

9.3.6 Two-Way Portable Equipment.

9.3.6.2 Portable radios shall be manuactured or the environment in which they are to be usedand shall be o a size and construction that allow their operation with the use o one hand.

9.3.6.3 Portable radios equipped with key pads that control radio unctions shall have ameans or the user to disable the keypad to prevent inadvertent use.

9.3.6.4 All portable radios shall be equipped with a carrier control timer that disablesthe transmitter ater a predetermined time that is determined by the authority havingjurisdiction.

9.3.6.5 Portable radios shall be capable o multiple-channel operation to enable on-scenesimplex radio communications that are independent o dispatch channels.

9.3.6.6 Portable radios shall be designed to allow channels to be changed while emergencyresponse personnel are wearing gloves.

9.3.6.7 Single-unit battery chargers or portable radios shall be capable o ully chargingthe radio battery while the radio is in the receiving mode.

9.3.6.8 Battery chargers or portable radios shall automatically revert to maintenance chargewhen the battery is ully charged.

9.3.6.9 Battery chargers shall be capable o charging batteries in a manner that is independento and external to the portable radio.

9.3.6.10 Spare batteries shall be maintained in quantities that allow continuous operation asdetermined by the authority having jurisdiction.

9.3.6.11 A minimum o one spare portable radio shall be provided or each 10 units, orraction thereo, in service.


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Porabl Raio Usr guiUsers and their behaviors have an impact on the eectiveness o reground communications. Humanactors, such as the way we speak and organization o reports, aect communications. Technical actorsobviously have an impact on reground communications. Like any other technology, users need to knowthe limitations o the technology and how to use the tool appropriately.

Hua Facors

When we talk on the radio, each o us subconsciously perorms a process beore we speak. Managing thisprocess will provide more eective communications.

Organization Before speaking, formulate what information is being communicated and put theinormation in a standardized reporting template. For instance, a standard situational report might containUnit ID, location, conditions, actions, and needs. This method orces users to ll in the blanks, answer allthe necessary questions, and lter out unneeded inormation.

Discipline Often, ICs are overwhelmed by excess information on the radio. Radio discipline on thereground will help to determine i inormation needs to be transmitted on the radio. I ace-to-ace

communications are possible between members o a crew and the inormation is not needed by the IC,dont get on the radio.

Microphone location Placing a microphone too close to the mouth or exposing the microphone toother reground noise may result in unintelligible communications. When transmitting in a high-noiseenvironment, shield the microphone rom the noise source. Hold the microphone a couple o inchesrom the mouth or, when speaking through a SCBA mask, place the microphone near the voice port onthe acepiece.

Voice level When speaking into a microphone use a loud, clear, and controlled voice. When users areexcited, the speech oten is louder and aster. These transmissions oten are unintelligible and require theIC to ask or a rebroadcast o the inormation, resulting in more radio trac on the channel.

Managing these human actors will have a positive impact on reground communications. Reporting shouldbe complete, necessary, and in a controlled, clear voice. These actions will reduce the amount o repeattransmissions on the reground, reducing air time.

tchical Facors

In some cases communications problems are caused by a technical issue. Users need to recognize technicalproblems and take corrective action to improve communications. Radio users oten blame the radio orsystem or coverage problems. In many cases user actions can improve communications.


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Position and Radio Location

As we know, reghting oten places reghters in challenging environments orcing them to crawl on thefoor. The optimal position or a portable radio transmission is at head height with the antenna in a verticalposition. The photo below shows a reghter on the foor. The radio is against the body inside o the radiopocket on the turnout coat. Some o the transmitted energy is absorbed by the body, and the antenna is ina horizontal position. This results in a poor radiation pattern and a reduction in range o the radio. Movingto a location where the reghter can sit up may improve communications, i transmissions rom the proneposition are not heard.

Many users do not use a radio pocket or case. In the middle photo above, the Company Ocers (COs)radio (let) is clipped to the exterior o the coat, while the reghters radio is protected. The tradeo isthat the radio is exposed to heat and steam but is in a better transmitting position. When unprotected, theradio may ail to operate when needed. Radio cases with shoulder straps provide little protection and are anentanglement hazard when worn on the exterior o turnouts.

U.S. Fire Administration Voice Communications Guide for the Fire Service - FEMA

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