The readers always write
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.”
“Please understand that I’m not anti-digital. I do think that digital vocoder technology will eventually improve to the point where it outperforms analog in fireground situations (indeed, the newest AMBE vocoders may already be there), but until it does, there is a clear and documented problem with the current P25 vocoder in noisy environments when compared to analog. Firefighters shouldn’t have to do anything different when switching from analog to digital to get similar performance. If they have to do something additional (i.e., better microphone placement) to get similar performance, then something is wrong with the new technology. Granted, better microphone placement is always a good thing, but it shouldn’t be needed to cover up technology failings.”
“Yes, firefighters can be poor radio users. But that is a separate and distinct issue from the vocoder problem. A test by a radio tech where the ‘radios performed well’ is quite different than a quantitative study by NTIA and NIST that methodically and scientifically provides performance data. Blaming firefighters for a well-known and documented technology problem is ridiculous. While I understand that the IAFC has been careful to not place blame for this problem, the fact of the matter is that a bunch of engineers and standards bodies dropped the ball, and it’s costing millions or billions of dollars. The blame can probably be spread many places, but it’s certainly not the firefighter’s fault that the vocoder barfs when background noise is introduced.”
“We have identified the issues with background noise. What has not been identified is the poor response of the vocoder to very loud voice transmissions, and likewise soft transmissions. I have female firefighter paramedics that simply cannot be heard even under the best conditions when working with a digital system. Same radio, same person, same scenario, and when in analog, everything is perfectly clear. If the user is excited and is louder than the intended environment, the same type of event occurs: scrambled, unintelligent audio. Now, I will agree, that training is an issue. But I must also contend that if someone’s life is on the line—they have been trapped in a collapse, have a gun pointed at their chest, or have been seriously injured—there is no second chance, no ‘can you repeat your message?’ Then it is too late to blame the end user for the shortcomings of the technology.”
“Another issue that people seem to miss is the totally unintelligent thrashing-type noise that comes out of a digital system during loop-back feedback. When we put multiple radios together on a fire ground, not only do you have plenty of background noise, but there are also plenty of radios with lapel microphones turned up to their maximum volume so that we can hear over the background noise. When someone transmits a message in the middle of this mess, the longer the transmitter is keyed the worse the noise becomes. We have moved fireground operations back to analog due to that issue. We do not have the luxury to tell our firefighters, EMS personnel and police to perform a sequence of events when life is at stake. We must demand of the industry to provide the average user with simple communications solutions, even if built upon complex platforms.”
So there you have it. We’ll be writing more about this—and I’m certain our readers will too. To borrow from contributing writer Harold Kinley—who along with Jay Jacobsmeyer writes the engineering features for Urgent Communication’s print edition–stay tuned. In the meantime, thanks to everyone who wrote. We appreciate the feedback, and the insights. We’ll share more of the responses in a future edition.
E-mail me at
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