I hope that you consider NOT using digital on fire ground channels. Dispatch,command, call in are ok, and water source maybe ok for digital, depends how you use them. I personally wouldn't use any digital mode made by any manufacturer for any use that has any background noise, whether it be a diesel engine screaming at 4000 rpm for pumping, an air alarm on an airpack, or 2-cycle power tools. Hopefully the FCC has seen the light on analogue frequencies for firefighting fire ground use, and won't push the 6.25kc digital in 2020.
As far as monitoring Fire Ground operations, all it takes is a LOT of remote receivers at a LOT of the tower sites. I read somewhere recently that FDNY has started doing just that, and sending the information back on a talkgroup on their new trunking system. The only difference is they are still analogue.
All fireground simplex communication will be analog VHF. We already have the tower sites, it's just the equipment that needs to be updated. They have estimated coverage in the upper 80% range on the simplex VHF side, which is far better than it currently is. There will be over 90% on the digital side from what I'm told.
Based on our tests I'm not so quick to discount the abilities of the noise cancellation abilities on the digital side. I'm not sure if you watched the video or not, but our test did feature me talking with the pump running at 150 psi behind me continuously. The radios didn't do too badly in digital for that test, but they often did better in analog. We have done a lot of the same tests pictured in the video from radio to like radio with power saws running, extrication tools operating and numerous types of PASS alarm. The results shown in the video are all consistent with the results of those tests.
A few manufacturers have noticed our video, and like I said, we will be doing another video. We may be getting radios with some tweaking done to the programming and firmware, and we are still considering how to have a non-bias receive site for our test.
The other monkey wrench that we are trying to figure out how to throw into the mix is the use of a lapel speaker mic. It's very rare in the fire service that we don't use one on our radio, however there are so many out there that it's hard to have a test like we've done be even close to valid without having one of each kind. We’ve found out that the APX radio only picks up and filters audio from the speaker mic when it’s attached, whereas on the Harris multiband radio the speaker mic, AND the two mics on the radio are all still active with the two radio mics acting as the primary background filters. This was a very interesting development and has us working to try and get a Harris radio for testing. The problem is that APX radios are already out there (we own three) and the Harris radio is very difficult to come by and not being shipped yet.
Perhaps some of our testing will give the NIST people some ideas for their big test. I'm crossing my fingers that we can find a way to go out there and be involved. Heck, we just want to watch!
Brad A. Ingersoll
Asst. Chief
Maple Bluff Fire Department
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