The readers always write

Aug 29, 2008 12:29 PM, By Glenn Bischoff

More From Commentary

Now and again, we turn this space over to our readers. There are several reasons for this. One is that we believe that this newsletter, and our Web site, should be a conduit for discourse. (In fact, we recently added to our site—www.urgentcomm.com—a mechanism for readers to weigh in on selected stories and commentaries.) Another is that we enjoy a passionate and engaged readership, of which I was reminded when my e-mail box lit up like a pinball machine after last week’s column on the problems digital radios are having on the fireground.

There has been much discussion lately regarding digital radio’s alleged inability to distinguish voice from background noise when used in high-noise environments such as those found on the fireground. I had reported on tests conducted by a radio technician in Florida that replicated several of the conditions firefighters typically encounter. He said the digital radios performed well and suggested that a solution to the problem could be found in providing firefighters with specific training on how to best use a digital radio in a high-noise environment.

One of the readers I heard from was the technician, Terry Forehand, the systems manager for Nassau County, Fla., who was concerned that I had portrayed him as being critical of firefighters and asked me to clarify his position. So be it. “It is not my position that the problem with digital audio is the firefighters. You can’t train a person to make a radio perform better or worse,” he wrote. “The key point is that firefighters need to be trained on the differences between digital and analog radios and how they perform differently in noisy environments.”

The following is a sampling of other reader comments, edited for length.

“As a firefighter and radio geek, I'll be the first to agree that firefighters in many areas are very poorly trained in radio usage and that needs to be addressed. However, as an electrical engineer, I also feel that the current Project 25 offerings are a problem for firefighters, and the NTIA study proves it. Analog has a clear advantage over the current P25 vocoder when it comes to background noise performance. If the new digital system provides better coverage or more capacity than the system it replaces, then the those advantages need to be weighed against the disadvantages of poor vocoder performance in high-noise environments. If everything else in two systems is equal (coverage, capacity, etc.), then analog wins for fire-service use.”

“In a typical fireground environment where simplex communications are used (resulting in a high RF signal-to-noise ratio), I cannot think of a single advantage of using digital voice that even comes close to outweighing the risk of a vocoder failure in a noisy life-threatening environment. The three main advantages of digital communications are encryption, better fringe coverage performance, and better spectral efficiency. Encryption is generally not needed or even desirable in the fire service. While fringe coverage can be a real advantage of digital, if a system is properly designed, users should not be operating in fringe coverage areas. Spectral efficiency is a worthy goal, but it should never, ever come before responder safety.”