Analog LMR is easy to use
Analog LMR radios have volume and channel controls and a push-to-talk button. All can be accessed easily, even by fire fighters wearing gloves. There is typically no need to look at the radio. P25 radios have useful capabilities like encryption and channel trunking that enhance security and enable interoperable talk groups to communicate with other agencies. Inevitably, these features add complexity to operating P25 LMR.
Analog voice requires agencies to be on separate frequencies
Early analog LMR system used amplitude modulation (AM) signals, which work identically to AM radio stations. For several decades, analog LMR has used standard frequency modulation (FM), because it is less susceptible to noise interference. Because FM is extremely simple, incompatibility between the analog LMR equipment provided by different vendors hasn’t been much of an issue.
The biggest “incompatibility” issue with analog LMR has been that the only way to keep nearby agencies from interfering with each other, precisely because their LMR could hear other agencies transmitting on the same frequency, was to use different frequencies. Consequently, agencies that did not have multi-band radios capable of transmitting on other agencies’ frequencies could not communicate by LMR with personnel from the other agency.
Public safety organizations, led by the Association of Public-Safety Communications Officials (APCO), developed the P25 digital voice standard to facilitate inter-agency communication. However, even after 22 years of development, compliance with the standard does not guarantee that equipment from different manufacturers will be able to communicate. Consequently, NIST and the National Telecommunications and Information Administration (NTIA) have created the Project 25 Compliance Assessment Program (P25CAP) to test P25
Public safety agencies have been strongly encouraged to purchase equipment that has passed P25CAP compatibility testing. Still, many agencies choose to purchase incompatible equipment, many times because it costs less or has more useful features than certified P25 equipment. Organizations are most concerned that the units are compatible within the agency, and compatibility with the equipment of other agencies is not always considered sufficiently important to justify paying compatible P25 equipment’s premium cost. Some agencies, like volunteer fire departments, simply cannot afford equipment that would be compatible with surrounding agencies.
Analog LMR is far less expensive than P25
Even the smallest public safety organization can expect to spend tens of thousands of dollars converting to P25, because when infrastructure and lifetime operating and maintenance costs are added, the cost per P25 radio exceeds $10,000. That puts the wholesale replacement of analog LMR subscriber units and infrastructure beyond the reach of many smaller state and local public safety organizations.
Faced with a choice of no cash outlay to stay with existing analog systems versus the considerable investment to convert to P25, which in many ways is outperformed by analog voice, many organizations have delayed the conversion. Consequently, organizations that have made the jump to digital have no choice but to retain analog capabilities.
Making it all work together
The pace of evolution in public safety communication and information systems continues to accelerate. During the 20th century, field personnel relied on analog LMR and land-based telephone systems to communicate with one another and with their dispatchers and commanders. No new communications tools were added for 80 years until public safety started using commercial cell phones. Less than a decade later, digital cellular services were added to PCs in vehicles and P25 LMR systems rolled out. A couple of years later, smartphones allowed access to data services by personnel on foot.