Interoperability between different radio systems
firefighter479,
Interoperability isn't rocket science anymore like it was prior to the early 1990's and today agencies do not have to be operating on the same system, in the same frequency band or even use the same digital format (i.e. P25, MotoTRBO, Nexedge, etc.) to have the ability to communicate with each other, even though some radio manufacturers want you to think that. Cities and counties do not need to spend millions of dollars to have the ability to talk to each other during the monthly or annual joint incident. The problem here is the majority of the lead decision makers, like the Sheriff, Police Chief, Fire Chief, EMS and EMA Directors who must convince the County Commissioners and City Councils to approve major expenditures, like two-way radio communications equipment, don't know or understand how two-way radio systems work, nor do they have time to "think outside the box" when it comes to ways of making interoperability happen. Another problem is agencies do not seem to want to use the interoperability channels in VHF, UHF, 700 and 800 MHz for some strange reason and think they must all be on the same system in order to communicate (HOG WASH!). Agencies like Grovetown city and McDuffie, Lincoln, and Warren counties that have switched to NXDN/Nexedge or Jackson, Paulding, Polk and White County that have switched to MotoTRBO have not backed themselves into a corner when it comes to interoperability if they take a little time and a very small amount of money to purchase equipment needed and work up a plan to communicate with their neighbors and others . Even though McDuffie, Lincoln and Warren Counties have migrated to NXDN/Nexedge on VHF, I'm sure they left the analog VHF Mutual Aid Channels in their radios so they could communicate with other agencies. You were on the right track when you spoke with your former fire chief about MOUs and putting some VHF portables on the fire apparatus, but the problem in using VHF portables is they are used so infrequently the batteries are not reliable. One of the best interoperability solutions I have used in the 33 years I have worked in public safety communications is a mobile mounted Motorola GR300 VHF to 800 MHz cross band repeater because it puts the control of interoperability in the hands of the user and it allows the user to take it anywhere they go. It consists of a VHF mobile radio, an 800 MHz mobile radio both linked together with a Motorola HLN3333 Repeater Interface Kit (R.I.K.) and can link any two channels programmed into the two radios at the touch of a button.
A good example I like to use is County "A" operates on an 800 MHz P25 Phase 1 System for normal day-to-day operations and County "B" operates on a VHF analog conventional system for normal day-to-day operations. Both agencies have installed a mobile radio in the band the other county uses and have interfaced it to their primary radio with a R.I.K. in the fire engines closest to the county line so they can "patch" channels and or talkgroups together as needed when working a joint incident. A major interstate highway, say I-20, runs through both counties and a multi-vehicle accident involving three tractor trailers, a motor home, two pickup trucks and five cars occur right at the county line with persons trapped in some of the vehicles and two vehicles are on fire, plus a hazardous material is on board one of the tractor trailer trucks. The company officer on the first due fire engine from County "A" either learns of or requests a fire response from County "B" and establishes contact with County "B's" responding units on their VHF channel to coordinate the response and determine on scene communications with the company officer of the County "B" fire engine. It is decided County "A" fire personnel will operate on the 800 MHz talkgroup named Fire TAC #1 and County "B" fire personnel will operate on the State Fire Mutual Aid Channel in VHF, so upon arrival at the scene the company officer on County "A's" engine selects Fire TAC #1 on the 800 MHz radio in the engine and State Fire Mutual Aid Channel on the VHF radio in the engine then presses the "ENABLE PATCH" button on the R.I.K. to link the audio of the two radios together. The company officer on County "A's" engine transmits a message on both radios advising "a cross patch between County "A" Fire TAC #1 and State Mutual Aid has been established for the multi-vehicle pile up on I-20 at the County Line". The company officer on County "A's" engine disembarks the apparatus and keys up his 800 MHz portable radio to give a visual report of the scene to his 9-1-1 Center and other responding units and his/her transmission is automatically simulcast over the State Mutual Aid Channel so responders from County "B" can hear his/her message and can talk back to him if needed. All responders from County "A" at the accident scene operating on 800 MHz Fire TAC #1 can talk to all responders from County "B" operating on the State Fire Mutual Aid Channel during the duration of the incident. The cross patch of the 800 MHz Fire TAC #1 talkgroup and State Mutual Aid Channel remain in place until the incident commander deems it is no longer needed when all personnel from one of the two counties have left the scene.
Sound complicated, not really and probably not much more than changing zones on a portable radio. Sound time consuming, not really and probably not taking much more time, if any, than changing zones on a portable radio. Remember, the key is coordinating the response between the two agencies while enroute and having a communications plan before arrival (i.e. which channel and talkgroup will be patched and who will establish the patch because only one R.I.K. needs to be activated on the same channels). Sound expensive, definitely not because County "A" already has an 800 MHz radio in their fire engine, so all they have to do is purchase a 25-50 watt mobile radio, such as a Motorola PM400, for around $450 and the Motorola R.I.K. (HLN3333) for $280, so for a little more than $750 County "A" can install an interoperability gateway in an engine. If County "A" wanted to equip five fire engines, two rescue trucks and a ladder truck with a cross band repeater then it would be a little more than $6,000.00 total which is about the cost of one Motorola APX dual band radio. Can you believe it! On the other hand, it will cost County "B" a little bit more because they already have a VHF mobile on their apparatus, so they would need to purchase an 800 MHz radio and the R.I.K. them interfaced with their VHF radio (Example: Motorola XTS1500 for $1,700 and R.I.K. for $280, plus installation). Still not a bad price at all considering if County "B" were to move to an 800 MHz P25 System it could cost them over $10,000 per fire engine if they purchased a mobile radio and four 800 MHz P25 portable radios for each fire engine.
Oh and the other good part about this type of interoperability solution is County "A" and County "B" can still have interoperability with other agencies even when they are outside the coverage of their home radio system. An example of this would be for the company officer on County "A's" fire engine to put the 800 MHz mobile on 8TAC92 Direct and the VHF mobile radio on the State Fire Mutual Aid Channel then "patch" the two channels together and have each County "A" firefighter to put his/her portable radio on 8TAC92 Direct. This gives them direct voice radio communications with whatever department is operating on the State Fire Mutual Aid Channel. This applies to any VHF channel programmed into the VHF mobile radio that is selected, so whether it is State Fire Mutual Aid, a VTAC channel or a VHF fireground or fire TAC channel used by a neighboring county, if it is in the VHF radio you can make the 800 MHz portables talk on it.
One more thing, for counties or cities that primarily operate on an 800 MHz System now, but still maintain their VHF base station/repeater to backup the 800 MHz System in the event of a catastrophic failure of the 800 MHz System there is no longer the need to maintain VHF portable radios on fire apparatus or store these portable radios in a closet in a fire station or in the E.O.C. if cross band repeaters are installed in fire apparatus. This is because the R.I.K. allows 800 MHz portables on an 8TAC or other 800 MHz analog conventional channel to access the VHF base station/repeater systems. Another benefit, no need for personnel to deal with dead batteries when the VHF portables are deployed, no need to purchase or maintain VHF portable radios, that is unless you just want too.
I apologize to you and others reading this post for writing a book on this topic, but I felt you needed some detailed information to help explain this concept because more than likely you will not hear this from the vendors of large 700/800 MHz P25 trunked systems.
Hope this helps.
