Fireground Communications article

[Phaedrus]

I found this interesting article in my research trying to better understand the radios that so many (myself included) take for granted.

At this point, I think I will be studying up for my Amateur Radio Tech License so that I will have a more thorough understanding of what goes on with our radios.

Original PDF:
http://www.cdc.gov/NIOSH/fire/pdfs/FFRCSch1.pdf

NIOSH Firefighter Radio Communications
TriData Corporation 1 September 2003
CHAPTER I: INTRODUCTION
One of the most significant problems facing firefighters within a structure on the
fireground is the ability to communicate reliably between the firefighters themselves and
between the firefighters and the command post or communications center. In an ideal
world, firefighters would be able to communicate with one another and the command
post at all times, regardless of where they are or what they are doing. However, this is not
the case.
Over the past decade, incidents involving firefighter injuries and fatalities have
demonstrated that, despite technological advances in two-way radio communications,
important information is not always adequately communicated on the fireground or
emergency incident scene. Also, the events of September 11, 2001, and other emergency
situations in recent years have highlighted the need not only to improve firefighter radio
communications, but also the communication systems available to law enforcement
personnel, emergency management officials, and other public-safety responders. Equally
important is the interoperability of all of these systems.
The continued incidence of firefighter fatalities where communications are cited as a
contributing factor as well as the industry-wide lack of consensus on the appropriate
frequencies to use in fireground communications have prompted NIOSH to more
thoroughly investigate fire department communications and its problems.
Scope of Work
This study seeks to identify and address specific deficiencies in firefighter radio
communications by researching the types of radio communication systems currently in
use by the fire service and identifying what problems exist with them; identifying current
technologies of interest to firefighter communications; identifying knowledge gaps
regarding the effectiveness of such technologies; and finally, make recommending future
research to improve firefighter radio communication and personnel location. In particular,
this study focuses on communications problems caused by inadequate radio frequency
(RF) signal propagation within a structure during firefighting operations and to and from
the structure to the incident command post (ICP) or dispatch center.
The scope of work is described in more detail in Chapter II, “Methodology.”
Types of Radio Systems
Currently, most fire departments in the United States use conventional analog or digital
mobile two-way radio technology operating in the 30–50-MHz band (VHF, low band),
150–160-MHz band (VHF, high band), 450–470-MHz band (UHF), and more recently
the 800-MHz band. [77,314] Which type of system a fire department uses has both
historical and technological reasons. Historically, the communication systems were first
available in the lower bands. In terms of technology, communications systems have been
chosen according to atmospheric propagation characteristics and to a lesser extent by
structure propagation characteristics. For example, the lower bands propagate further
through the air than do the higher. In a rural area, this is a plus as it allows coverage from
a base over a much longer range, which keeps costs and complexity down. In an urban
area the long range can be a minus as the radio environment has many more users within
range and interference is a big problem.
Very high frequency (VHF) is the part of the radio spectrum from 30 to 300 MHz. VHF
radio systems, either low band or high band, are simplex systems—messages are sent
only one-way at a time. The low band provides relatively long-range coverage from base
to mobile units but suffers from skip interference caused by distant low band signal
skipping off the ionosphere and interfering with local radio transmissions. The high band
also has problems with interference from mobiles up to 50 miles away and can only give
reliable hand-held-to-hand-held communications for about ¾ of a mile unless the radio is
elevated more than 5 feet above the ground. High-band VHF systems typically need to
use repeaters to provide area coverage. Although, VHF has superior structure penetration
in comparison to UHF [77], VHF’s susceptibility to interference makes it a poor choice
for urban use. Many rural systems use VHF radios because of their range, and because
their relatively uncrowded RF environment does not cause unacceptable interference.
Ultra high frequency is the part of the spectrum from 300 to 3000 MHz. These ultra high
frequency channels do not have the range of the low or high band frequencies of the
VHF, and typically require the use of repeaters to have the same coverage as low or high
band VHF frequencies [84]. Conversely, because of the shorter range and the lack of skip
propagation, they do not suffer from the interference problems of the VHF bands.
VHF and UHF, except 800 MHz, are conventional radio systems. In a conventional
system, a group of radios share one fixed channel or frequency. If that channel is in use
by one user in the workgroup, service is not available to others.
The FCC has designated parts of the 800-MHz to 900-MHz radio frequency (RF) band as
public safety radio frequencies for use in public safety trunking radio systems. Trunked
systems, which are usually computerized, allow more efficient use of frequencies. In a
trunked system a set of radio channels (a trunk) is assigned under computer control.
When a firefighter transmits, a computer automatically assigns the firefighter to an open
frequency. When the firefighter ends the transmission, the frequency is automatically
made available to the next firefighter transmitting [315]. The operator does not have to
manually select a frequency. Because these systems have multiple frequencies and they
are only assigned while a radio is actively transmitting, they provide higher capacity than
conventional VHF and UHF radios. This helps prevent radio system congestion. The high
capacity of these systems and low interference from other users of the public safety
trunking band make these systems appropriate for use in congested areas.
No band of frequencies is perfect; many frequencies work well. The selection of
frequency is dependent on a variety of factors, including “frequency availability, area to
be covered, type of terrain, number of radio units required, frequencies used by bordering
fire [or public safety] districts, mutual-aid agreements, type of operation, and use of
emergency medical radios.”[315]


Communications from Inside a Structure to the Outside or Vice Versa
Fireground communication has significantly changed over the past decade with the
proliferation of the portable radio. In the fire departments reviewed, each firefighter team
of two will typically carry a small portable radio. In some fire departments each
firefighter has their own radio. The increase in number of portable radios coupled with
the multitude of communication systems has prompted many fire departments to
reexamine their radio procedures, and develop new fireground communication protocols
to aid in controlling radio traffic.
The focal point of all fireground communications is the command post. Typically, the
command post will be positioned as close to the incident as safely possible to facilitate
the communication process. The type of fire and the type of structure involved dictates
the location of the command post. Structures such as high-rise buildings, tunnels, and
sub-basements may disturb the effectiveness of portable radios and communications. In
these situations, some fire departments may position the command post inside the
structure to compensate for the portable radios’ weak RF output. For example, on fires
located on the upper levels of a high-rise structure the command post may be established
several floors below the fire (as opposed to the street level) to help improve
communication.
In the fire departments reviewed, each department had more than one tactical radio
channel for fire operations. Typically, once the command post has been established, fire
ground units are switched off of the main dispatch channel to a tactical fire ground
channel. These channels usually have a restricted range that permits fire ground units to
communicate independently of the main dispatch channel, and also prevent the bleedover
of other radio traffic from other fire units operating in the vicinity.
Firefighters operate as a team consisting of two or more personnel. Each interior team
can have one or more portable radios. To help control traffic, all radio communications
with command post is normally made by the unit officer or the senior team leader.
However, if fire conditions restrict visibility, team members may have to communicate
with each other by radio, which can substantially increase radio traffic. Some
departments restrict the use of individual portable radios to only emergency situations
where firefighter may become separated or trapped.
The operation modes commonly used in fire department communication systems include
simplex, duplex, and trunked.
The simplex mode requires both a transmitter and receiver at each end of the
communications path. In simplex mode, only one end (i.e., the transmitter or the receiver)
may operate at a time. It requires only one frequency. Only one firefighter may transmit a
message on a portable radio while using a simplex channel, all others must receive.
During interior fire department operations, firefighters may switch to a simplex channel
because their low-powered radios cannot transmit outside the building. Simplex channels
do not require the use of repeaters or towers. Rather, the portable radios themselves act as
the transmitter and receiver sites.
Duplex mode uses two frequencies that allow both ends to communicate simultaneously.
Thus, one user may interrupt another to facilitate discussion. Repeaters may be used in a
duplex system. Repeaters, typically located in a high place such as a mountaintop or tall
building, receive a transmission from a radio (in the system) on one frequency and
retransmits (or “repeats”) on another. Repeaters can also be located in fire apparatus and
command vehicles for use on particular incidents where communications are problematic.
All radios with proximate distance will receive the transmission from the receiver.
Repeaters are used to augment the range of the radio system.
Repeaters also allow a low-power portable radio to hear other radio messages (to, from,
and within a structure) when obstructions may normally hinder communications.
Sometimes, even in the presence of a repeater, obstructions are too great and will prevent
a radio signal from being transmitted.
A trunked system, which may include a single user or different workgroups, uses a group
of radio frequencies (a trunk). The system is dynamically controlled by a computer,
which directs a transmission to an available channel or frequency.
Firefighter Radio Communications Problems
Communication problems encountered by firefighters (and others) can be broadly divided
into two categories. First are mechanical or technical issues related to unsuitable
equipment, radio malfunction, system design, inadequate system capacity (too much
radio traffic), and failure due to extreme environmental conditions (e.g., fire, heat). Poor
and mottled radio communications in large structures have also been a persistent
problem. Another technical issue is interoperability, or the ability for various departments
(e.g., fire, police, public works) to communicate with each other or another neighboring
jurisdiction. The second category of problems relates to human factors.
In many instances, a variety of mechanical and technical issues such as RF attenuation,
fading, and building construction can prevent the system from maintaining sufficient link
quality for reliable communications. In large multistory structures, for example, the
frequency may bounce of the walls and windows with reflective coverings, or simply be
absorbed from the construction of the building. Some of these cases involve situations
where a firefighter is in danger and most in need of communications. As a result, this lack
of reliable communication could severely compromise the effectiveness, the safety, and
even the life of the first responder.
Human factor include radio discipline, training, tactical decisionmaking as well as others.
These factors combine with technical and equipment issues to adversely affect firefighter
radio communications. As such, these factors are considered as a component of the
overall analysis.



One of the most interesting comments about radio communications noted during this
research is: "Our [the fire service] radio systems aren't failing, but rather we can't get the
signal throughout buildings with 100 percent accuracy . . . this is affected by building
construction, windows, elevator shafts, the output strength of the system, and the
[strategic design and implementation of infrastructure such as the] presence of
repeaters."1
Organization for the Report
The remainder of this report is divided into five major sections, each addressing one
aspect of the study. The first section, Chapter II, reviews the study research methodology.
The second section, Chapter III, discusses the overall firefighter communication
problems, both technical issues and human factors. It also presents an overview of these
communication issues as well as a review of communications issues that affect fire
departments everyday. The third section, Chapter IV, examines the communication
problems inherent in structures, and the risk to firefighters. The fourth section, Chapter
V, discusses the results of the research and includes descriptions of available
technologies of interest, their current applications, potential applications, limitations, and
areas needing further investigation.
The report has two appendices. Appendix A is a tabulation of prioritized project issues,
and Appendix B details the communications problems of 24 jurisdictions, both large and
small. A Glossary of Terms and Abbreviation follows the appendices. The report
concludes with a Master Reference List containing more than 350 citations used in the
preparation of this report.
1 Telephone conversation with Deputy Chief Jeff Coffman, Fairfax (VA) County Fire and Rescue
Department.

[Pelican631]

I applaud you for wanting to become more familiar with your equipment. We train all the time on pumps and hoses and ladders but almost never get to know the radio. Here are some materials I've put together on the subject:

http://radioetcetera.googlepages.com/radiotraining

Andy