Project 25 Technology Information Group

Saturday, March 23, 2019

Project 25 Technology Information Group

Project 25 Technology Interest Group

P25 System of the Month – May 2016

Iowa Multi-County Radio System


Six Iowa Counties connect their separate P25 systems together for a unique blend of local control and regional interoperability

Six large counties in Iowa – Polk, Marshall, Grundy, Linn, Johnson and Blackhawk – are connecting their separate Harris 700/800 MHz P25 simulcast trunking systems together in an effort to reap the benefits of region wide coverage and interoperability while still retaining local control of important system design criteria like in-building coverage, capacity and local redundancy.  


Johnson County, Iowa (county seat of Iowa City and home to the University of Iowa) released an RFP in 2008 to replace their outdated analog 800 MHz trunking system with a P25 system.  Harris won that bid and installed the 800 MHz P25 trunked simulcast system in 2010.  Johnson County’s immediate neighbor to the north, Linn County, released an RFP in late 2010, also to replace their analog trunking system with P25.  Harris and their local partner RACOM provisioned the Linn County system so it was directly connected to the Johnson County system.  While each County has their own P25 central network core, each shares a redundant central database which makes them aware of the surrounding peers and their assets.  Each core is able to efficiently route talk groups and other traffic between the cores that have demand for it, while not sending information to the cores that have no need for it.  Since each core is fully aware of its peers, users are able to seamlessly and without end user intervention roam from system to system without concern for which county’s towers were being accessed.

According to Charlie McClintock, Communications Director with the City of Cedar Rapids in Linn County, IA, “We like being able to have seamless interoperability with our Johnson County partners and an extended coverage area into multiple counties without having to sacrifice important elements of our own system like having our own P25 network switching center resources and in-building portable coverage custom designed for us.  The Harris & RACOM solution allowed us to have the best of both.”

Growth to Other Counties

The positive experience in Linn and Johnson Counties got those Sheriffs to begin to collaborate with their neighbor to the north - Black Hawk County, IA.  Black Hawk County released an RFP to replace another analog trunking system with P25 in early 2015 and will be the third county to become a part of the expanding network late this year.

Three other Iowa counties: Grundy, Marshall and Polk, all recently upgraded their aging 800 MHz Harris EDACS-based land mobile radio systems to P25 through their partnership with RACOM.  The public private partnership has RACOM owning the P25 switch resources and most of the P25 tower site infrastructure in exchange for extended service and maintenance from the public safety partners.  These systems are also being connected to the network in a manner that creates wide coverage areas, seamless interoperability and intuitive roaming among all six counties.

Local Control

Many states, including Iowa, have built or are building state-owned and controlled P25 systems that allow local usage.  These six counties preferred this model because they can reap the benefits of wide area coverage and seamless interoperability that state systems offer without having to sacrifice the important local control elements of local redundancy, in-building coverage and seamless integration with other important systems like fire paging and 911 telephone.

Planning and Coordination

While the original Johnson and Linn County systems were designed to be a single system from the beginning, ensuring the other four county systems and other systems to be added in the future have similar system IDs, IP address schemes and non-conflicting end-user ID’s has taken careful planning and great coordination.  In collaboration with each of the counties key personnel, a single talk group and unit id plan was agreed to that allocated 500 talk groups (including several unallocated interoperability talk groups) and up to 10,000 unit id’s for each agency in a county (up to 100,000 unit ids total in each county).  

Collaboration – Open Standards

Collectively, the P25 systems in these six counties have nearly 100 separate public safety/public service agencies and 6,000 radios.  Departments not only have different requirements for their radios, but also vastly different budget capacities and timelines.  Open and competitive procurement of P25 end user radios is very important.  The Harris P25 infrastructure in these six counties is currently supporting P25 end user radios from Harris, Tait, EFJohnson, Motorola and Kenwood.

To see how your P25 System can be nominated as a P25 System of the Month


Stephen Nichols

Director, Project 25 Technology Interest Group

This email address is being protected from spambots. You need JavaScript enabled to view it.





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