Mission Critical Mobility Applications: A Challenging Fit Increasing with Time.
Antenna selection can often feel like an afterthought; the antenna is not merely an accessory, it's the foundational element dictating the entire system's performance, range, and resilience. RFI has a history of over 45 years working with emergency services and critical communications agencies to design and deploy antennas into mobility applications. This history has afforded us knowledge and expertise to design and manufacture antennas that are not only fit for purpose, but also leaders in the industry. As the interface between your radio and the people on the front lines, let’s dive into the elements affecting antenna choice for mission critical mobility applications.
Antenna selection in Mission Critical mobility applications takes a more considered approach than many other applications. There exists a delicate balance of trade-offs between performance and the practicalities within single bands, let alone when we look at multiband or multi-protocol applications. In modern critical communications, one vehicle can easily be running radios for multiple LMR/PMR networks, cellular, GPS, and satellite or IoT protocols. Being able to accommodate the antennas for all these applications on one vehicle, perhaps with mission critical specific requirements, represents an increasingly complex challenge in modern critical communications. Physics is a cruel mistress, and antennas are constrained by the limitations of the basic physics of how antennas and radios work. Much of the time, this is working against the constraints of space, both on the vehicle and vertical allowable height, a desirability for discrete designs, and the sheer number of antennas that are now required on a vehicle.
A Wide Range for Your Perfect Fit.
Antennas for mobility applications are not one-size-fits-all. While all our antennas uphold our basic design excellence of long-lasting quality, each design choice will have a corresponding concession. RFI has therefore designed a broad range of antennas to cater to different user needs, whether that be low profile, high gain, on-glass, or covert; all these features come with a corresponding compromise. Narrowing down the selection becomes a factor of knowing what features are imperative to the application and where compromises can be accepted. In mission critical applications, it is particularly important to ensure that the performance of the installation is expected, consistent, and prioritises the challenge at hand that needs to be solved.
Regardless of antenna frequency or technology, all RFI antennas are designed with only high-quality connections and materials that will last through the UV exposure and harsh vibrations associated with vehicle mounting and endeavour to maximise impedance matching and efficiency.
Only so much space, when a ¼ Wave Whip won’t fit.
While the benchmark for vehicle installations in terms of coverage performance will always be a ¼ wave whip on a ground plane, this installation comes with two major compromises: a very narrow bandwidth and the potential for a very long whip at low frequencies.
Especially in Australia and New Zealand, many applications persist where antennas based on a 1/4 wave whip are still the preferred solution. With wide and difficult expanses, heavy foliage, and sparse populations, prioritising pattern performance and VSWR to increase the edge of coverage, ensures continual connectivity of critical personnel. Even with the higher cost associated with coupling multiple narrowband antennas to one radio, this solution is still preferred, even if this means higher costs and a more complex installation. Where there is space to sufficiently separate antennas when mounting, and the very low noise floor is required, the ¼ wave whip is still an exemplary solution; the challenge is that there is now rarely enough space. In these cases, a mixed solution can be used, where multi or wideband antennas are used for most frequencies, but key or difficult frequencies, such as VHF, use a narrowband antenna.
As networks have become more complex, vehicle installations now have to support both multiple technologies and more complex networks. Looking at cellular alone, these commonly only needed to cover 1 or 2 bands in the 90s with 2G, now coverage of 6-8 bands is the minimum expectation. Similarly, we are also seeing an increase in complexity in the traditional LMR radio networks. Most police and fire agencies across ANZ now need to utilise both VHF and UHF frequencies or use multiple UHF frequencies.
Coupling every narrowband antenna across a single vehicle has become an impossible task, making multiband or broadband antennas a necessary compromise. The complexity in increasing bandwidth in antennas has a relationship with the technology being used and the frequency. This is why multiband cellular antennas such as our industry leading Meander CDQ series have been available for a while now. This also makes combination antennas with Wi-Fi/ Cellular/ GPS, such as our Legion series, relatively simple to produce; the pattern and return loss requirements from the antennas are less stringent, and the frequency range is easier to combine without significant changes to pattern and return loss characteristics.
Wide and multiband mobile antennas for LMR radio systems, including P25 and DMR, at UHF frequencies and especially VHF, pose significantly more of a design challenge. RFI’s expert engineering has allowed us to design and manufacture antennas that have incredible wide and multiband performance despite these challenges. With RFI’s exemplary design, we have overcome typical multiband antenna issues, including ensuring exceptional pattern performance at all frequencies and increased return loss despite the electrical length mismatch at broadband UHF or dual band VHF/UHF frequencies, allowing for the industry renowned performance of the CD61 and CD30 series antennas to approach that of single narrowband antennas. With these wideband and multiband designs, RFI continues to provide antennas that first responders can rely on in increasingly complex networks.
Mount Me Anywhere
As the number of antennas increased, a new problem arose: there is only one centre of the roof, and not all the antennas can be mounted there. Emergency services vehicles also carry unique challenges of height and rooftop equipment that can make roof mounting difficult or impossible, further restricting the roof mounting capacity and possibility. RFI’s development of matching circuits has allowed for ground independent mounting of many of our antennas, including our outstanding VHF narrowband antennas and the CD61 Series Wideband UHF antennas. Responding to these evolving market needs makes mounting more flexible as alternatives become accessible, such as light bars, bonnets, and gutter mounts.
We have also increased the range of low profile and shorter antennas, such as the widely used CSM700 low profile cellular antenna, or the extensive range of transit LMR antennas, including the TLA600.
Further iterations of antennas, such as our CD990 series wideband elevated feeds to mount to clear obstacles such as light bars and bonnets, reflect RFI’s adaptation to the needs of the critical communications markets.
These ground independent antennas perform with little difference to the classic ¼ wave whip, making ground independent antennas the ideal choice for applications where performance is the goal, but mounting flexibility is the main priority.
Antenna, What Antenna?
Almost unique to critical communications applications is the need for discrete and covert antennas. RFI has designed and manufactured antennas for covert and discrete applications, including on glass and other alternative mounting positions. While these antenna designs come with significant disadvantages in pattern, gain, grounding, and physical obstruction, as well as having significantly restricted bandwidths, they meet an incredibly niche and specific requirement. This ensures connectivity even in the most unusual of circumstances.
Innovation to Rely On
Looking back at our catalogues from the 1990s, where RFI mostly featured narrowband, field tunable, or ground independent antennas, to the expansive and diverse antenna range existing today, it is clear to see why RFI continues to be a top choice for mission critical mobility antennas.
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Author: Monique Merino, RFI Product Marketing Manager.
