Sep 8, 2009 11:17 AM, By Donny Jackson

Early in 2007, the International Association of Fire Chiefs (IAFC) alerted its members to reports that the digital handsets used in many new radio systems were incompatible with the ambient noise frequently found in most fireground situations, including alarms from breathing apparatus and nearby chainsaws.

These anecdotal reports were largely confirmed in an IAFC report released last year that detailed the outcome of several objective tests on the subject conducted in 2007 and 2008 by the National Institute of Standards & Technology (NIST)/National Telecommunications & Information Administration (NTIA) laboratory in Boulder, Colo. Three types of systems — 25 KHz analog, P25 full rate and P25 enhanced full rate (12.5 KHz analog was tested on a limited basis) — were tested in nine environments.

All systems tested met National Fire Protection Association standards of 80% intelligibility when no self-contained breathing apparatus (SCBA) masks or background noise was involved. In addition, all systems failed to deliver intelligible communications in four of the nine fireground environments tested. However, when a firefighter uses an SCBA mask or personal alerting safety system (PASS), digital systems often were not as intelligible as analog systems, according to the NTIA report.

News of the tests spread like wildfire — pardon the pun — within the first-responder community. Many firefighting departments and unions brought the test results to attention of elected officials. In some cases, plans to migrate to a digital radio system were put on hold; more often, firefighters demanded that analog communications be used on the fireground until digital radios were proven to deliver intelligibility that is at least as good as analog.

In Saginaw County, Mich., the county conducted a test that demonstrated that the statewide radio network — a digital system—was as intelligible on the fireground as the county’s existing analog system before switching operations to the digital system.

Meanwhile, since the digital-radio issues were brought to the forefront, the vendor community has moved quickly. During the past year, Motorola and Harris RF have demonstrated the benefits of noise-cancellation features and other techniques leveraged in their new multiband radios in their trade-show booths. Meanwhile, digital vocoder technology continues to improve.

Despite the improvements, no vendor representative has made the bold claim that the digital-radio issue for the fireground has been resolved, only that progress is being made. While that seems apparent, such progress needs to be formally measured to get clear the air among many firefighters that digital radios are not as good as analog radios.

Some in the industry believe a new set of NIST/NTIA tests should not be done until digital radios begin including the new vocoder that DVSI is expected to release later this year. While the exact timing of the tests is debatable, it seems that an update to the tests conducted two years ago in a fast-moving portion of the industry is needed.

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