Your thoughts on digital trunked radio systems in the fire department.

Replies to This Discussion

Permalink Reply by Kim Fladung on April 15, 2008 at 3:26pm

John,

We have been using an 800 Mhz. digital trunked system in the Cincinnati/Hamilton County area for about 3 years now. The system was designed to provide 95% in building coverage when tested, which was achieved. Our county uses 24 antenna tower sites and so far we have experienced few problems.

We are currently attempting to use this system to also transmit data to mobile data computers in our apparatus. However, this system has not been working well for data since it's inception about i year ago.

Kim Fladung
Reading Fire Department

• ▶ Reply

Permalink Reply by Ben Stevens on May 8, 2008 at 7:36am

Our town placed a Trunked Digital system in service back in February. We have a some issues with department on the far end of town not being able to transmit out of basements. EMS knows that if they go to one of the hospitals in the city West of town that they do not have any service. Motorola has not said much as of yet due to a couple of pending lawsuits. The town is trying to resolve these issues.

We have found that if you have a couple of people with radios on next to one another and one of them transmitts you will get a echo that can overpower the person talking. A couple of guys in our office did a few test and found that if a PASS alarm or Vibra Alert is going off it can also overpower the person on the radio and cut off a radio transmission.

On our system we have Police, Fire, EMS, DPW, Town Gov't, two school districts & NYS DOT motorist assistance trucks. So far I haven't heard of anyone getting a busy signal when they were trying to talk due to there being to many people on the system.

• ▶ Reply

Permalink Reply by Bryan Downie on May 8, 2008 at 2:56pm

We went P25 compliant digital about a year ago and have had numerous problems with transmission quality and feedback. Fire companies on the fire ground could not communicate with each other on a regular basis. After much discussion and research we decided to use analog for all fireground operations and only use digital for dispatch purposes. This incapacitates our emergency PIN device as it requires a digital signal. The decision we had to make was, is it more important to use the emergency PIN and then not be able to communicate or was it better to forgo the use of the PIN but actually be able to transmit a Mayday and communicate. As a member of our local's safety commitee I don't like it, but unfortunately we could not find a viable alternative at this time.

On the IAFF website, click on Health and Safety, then Redmond Symposium. Click on Wednesday and then Communication Workshop. There is a lot of information about digital set ups on the video that will explain a lot of the pitfalls of digital. In a nut shell, digital is not practical in the fireground setting and was actually not designed for its environment.

The sad part is, the Fire Service is at the mercy of the radio industry and we have to adapt their technology to work for us, instead of them developing technology to meet our needs.

Good luck,

Bryan Downie

• ▶ Reply

Permalink Reply by Bryce Tracy on May 17, 2008 at 8:39pm

Hey John,

First I have to say I live in a rural area in MIchigan. We have both 800MHz Digital Trunked (MPSCS Radio System) and a county VHF System. The 800MHz system does work statewide with 97% mobile coverage and about 95% portable coverage. Yes there are buildings and known areas we have poor signal in but we manage. Also we use a two radio protocol....When we are dispatched we talk to Dispatch via 800MHz and upon arrival on scene, only the IC is requiered to have an 800MHz to continue communications with them as needed. The IC and all FF'S on the fire scene use VHF tactical or fire ground channels for on-scene communications. Remeber "internal and external" communications networks from ICS and NIMS training? Also our policy is to use the 800MHz on long distance tanker shuttles on an alternate talk-group/channel. This could also be done for ICS Comms....possibilities are endless here. Does your FD our City, County have a Communications Plan or Tactical Interoperable Communicatins (TIC) Plan? Remember Interoperable Communications doesnt mean just one radio or one system.....It means truly what it says.....Using all applicable radios and systems to communicate in a planned and efficent fashion. Why throw something away that works?? But if you can enhance your network even in just ICS formatting.....Then add to it....make them work together via a plan for true Interoperablity.

• ▶ Reply

Permalink Reply by Mike Walker on May 17, 2008 at 9:18pm

Hey John

I started a communications group a while back. There may be some discussions in that group that will help you in your quest.

• ▶ Reply

Permalink Reply by John Melfa on May 23, 2008 at 7:30am

Post the link. Is it on FIRE ENGINEERING? Thanks John

• ▶ Reply

Permalink Reply by Mike Walker on May 23, 2008 at 7:26pm

Yes its on this site. Communications is the name. It has a picture of a handheld radio as the icon.

• ▶ Reply

Permalink Reply by Drew Smith on May 26, 2008 at 11:48pm

Regardless of the bandwidth, NFPA 1221 requires all communication in the IDLH atmosphere/"hot zone" (inside a burning a building) to be on a simplex system. This means a single non-repeatered frequency that is the same for both transmitting and receiving. I have found that very few 800 systems use a simplex fireground freq. Whether you are repeatered the old fashion way or part of a trunked system the signal from the portable radio must travel to an antenna on a tower/structure, be processed by the equipment and rebroadcast before anyone else will hear it. So, if you are in the basement, in trouble and have a weak battery good luck. With digital it's all or nothing as opposed to analog which will give something. SInce at this time multiple band portables that are P25 compliant are either unavailable ro cost prohibitive using two radios seems to be the only option.

• ▶ Reply

Permalink Reply by Mike Walker on May 27, 2008 at 9:09am

That is great information, I didn't know about NFPA 1221. How long has the NFPA standard stated that?

• ▶ Reply

Permalink Reply by Drew Smith on May 27, 2008 at 8:21pm

More than a dozen years.

• ▶ Reply

Permalink Reply by Mike Walker on May 28, 2008 at 8:50am

That concerns me Drew. I wonder how many departments have allowed this to slip through? We do have "Direct Channels" which if memory serves, are simplex channels, but they are considered options that are to be used only for temporary instances.

• ▶ Reply

▶ Reply to Discussion