The L in LMR stands for land, but it might as well mean longevity. LMR has been around since the 1930s, but even with the arrival of 4G LTE, 5G, and FirstNet, it remains a fundamental part of mission-critical communications for public safety, transportation, defense, and utilities. Why?
One reason is reliability. Although LMR can be integrated with LTE, it’s designed to operate independently from any cellular technology. So if a natural disaster or terrorist attack takes out some or all of the mobile networks in a city, county, or state, LMR systems remain in service because they have their own infrastructure.
Coverage is another major benefit. The lower the frequency, the farther a signal travels. LMR uses VHF and UHF frequencies — primarily 30-50 MHz, 150-174 MHz, and 450-470 MHz — which are below most cellular bands. LMR systems can further boost coverage by using repeaters and transmitters that operate at much higher power than their cellular counterparts.
Another way to extend LMR’s geographic range is by linking multiple organizations’ systems over IP to create a regional or statewide network. This architecture also can accommodate LMR systems that work in disparate bands, providing interoperability so those organizations can communicate effectively.
The Project 25 (P25) standards enable interoperability between different types of LMR systems, including analog, digital, and trunked. The ability to bridge different technologies used by different organizations is another major reason for LMR’s longevity and continued relevance.
P25 standards also enable end-to-end encryption to prevent eavesdropping by unauthorized people. (For a deep dive into attack vectors, encryption options, costs, and more, see “The Who, What, When, Where, How, and Why of Encryption in P25 Public Safety Land Mobile Radio Systems.”)
One challenge that LMR shares with cellular is finding enough spectrum to meet demand. The FCC is continually reviewing licensees to ensure that inactive ones are removed and occasionally refarming spectrum used by other services so it’s available to LMR.
How to Choose an LMR-Grade Antenna System
A great antenna system is a must-have for a mission-critical communications system, and LMR is no exception.
One place to start is determining which bands it needs to support. For example, first responder vehicles frequently have radios for LMR, cellular, and Wi-Fi, as well as a GNSS receiver that uses multiple constellations. (For more information about how band requirements drive antenna choices, see “Narrowband vs. Wideband Antennas for Public Safety Applications.”)
That’s why Taoglas developed the Patriot series of antennas, which cover up to 18 bands spanning 4G, 5G, LMR, GNSS (L1 and L1/L5), Wi-Fi, and other technologies in a single enclosure. At just 205 mm x 180 mm, each Patriot model is compact enough to fit even the most space-constrained installations — including between the roof ribs on the Ford Interceptor, the most widely used police vehicle in the U.S.
The Patriot also is an example of two other specs to look for when comparing LMR antennas: IP and IK ratings. Its enclosure is IP69K rated, which means it offers the highest levels of protection against dust and pressurized boiling water damaging the antenna elements inside. It’s also IK08 rated, which indicates high resistance to hail, tree limbs, and other falling objects that public safety vehicles routinely encounter during disasters. (For more information about these specs and why they’re so important, see “How IP and IK Ratings Measure Real-World Durability.”)
Here’s what else to look for when choosing an antenna system for LMR applications:
- Customization. Sometimes an off-the-shelf antenna can’t meet an organization’s unique LMR requirements. Look for a partner that has extensive, proven experience in system-level design, optimization, testing, manufacturing, and validating antennas for mission-critical applications. One example is identifying potential sources of interference and suggesting solutions such as bandpass filters.
- Cellular Expertise. As LTE-LMR integration grows, so does the need for an antenna partner with extensive cellular experience — especially those involving public safety and other mission-critical applications, such as FirstNet.
- Innovative Materials. Antennas should be durable enough to withstand years of exposure to sunlight, driving rain, ice, hail, and even wildlife. LMR applications typically use whip or terminal‑mount antennas, where lightweight, flexible plastic or rubber materials are essential for minimizing antenna damage when they come into contact with other objects.
