A two-way radio system using a repeater may have great coverage except in areas, such as parking garages and basements of buildings, whose environmental factors create stubborn “dead” spots. In these locations, the repeater signal reaches the radio, but the handheld cannot reach back to the repeater. The traditional solution to this problem is to add Bi-Directional Amplifier and Distributed Antenna System within the building. Although this is a proven approach to get signals into problem areas, it can be complicated and costly. The complication comes from ensuring the signal is not overlapping the original in a manner that interferes with itself. The costliness is due to the need of running antenna coaxial cable from the amplifiers to the trouble zone, which may require many feet of cable and possible drilling through walls.
When there’s a need to extend the coverage of handheld two-way radios, the first option is usually a repeater. However, a repeater isn’t the full answer. A repeater will typically put out much more power and have a better antenna system than the portable radios with which it is communicating. This presents an unbalanced system where the transmit power of the repeater reaches much further than the transmit power of the handhelds.
Couldn’t this be resolved by turning the power of the repeater down to match the handheld? The reality is that often times mobile radios installed in vehicles and handheld radios are in use on the system. Mobile radios typically have greater transmit power than handhelds. Reducing the repeater power output to match the lowest powered device – the handheld – significantly constrains the system coverage, making the usable radius of the system much less than what it could be.
Icom recently attended an exciting conference that gathered top decision makers in K-12 school security. The overarching message from all of the attendees and speakers is the importance of relationship and communication with students, service and solutions providers. Communications technology plays a significant role in enhancing the ability to mitigate and quickly communicate root causes for incidences that unfortunately occur in our schools today. Instantly connecting all staff and security ensures that situation awareness is shared throughout the school and even the district. Communication response time confirms that an incident is managed at the lowest level of escalation.
Lithium-ion (Li-ion) batteries are very stable and reliable sources of power for two-way radios, laptops and many other devices. Lithium-ion batteries are widely used because they have a high energy density, resulting in a much lighter weight than other rechargeable batteries. Li-ion have other advantages too. They hold their charge well, losing about 5% of their charge per month as compared to ~20% for nickel-metal hydride (NiMH) batteries. Li-ion batteries have no “memory effect,” which means recharging them before they are completely discharged is not an issue. Li-ion batteries can handle many recharges before the end of their useful life.
FDMA (Frequency Division Multiple Access) and TDMA (Time Division Multiple Access) technologies are used in P25 and in business and industrial digital radios (P25 Phase I & NXDN™ for FDMA; P25 Phase II & DMR for TDMA).
The basic difference between FDMA and TDMA is the definition of a channel and how it is used.
In FDMA, a particular bandwidth (e.g. 6.25 kHz) at a particular frequency (e.g. 150.000 MHz) is used to define a channel. This is the way channels have been allocated in analog land mobile radios (LMR) for decades. All information is contained in the channel – compressed to the smallest frequency footprint. Analog radio bandwidth has recently shrunk from 25 kHz to 12.5 kHz, which is about the limit for analog technology without seriously degrading radio voice quality. With digital technology, channel bandwidth can be compressed to a spectrum-efficient 6.25 kHz by using vocoders and error correction.
“Intrinsic Safety” (IS) is a protection level for safe operation of electronic equipment in various explosive atmospheres. Petrochemical markets and other industries whose work environments may be exposed to explosive vapors as well as ignitable dust, fibers or filings benefit from use of Intrinsic Safety standards.
Each region of the world has its own standards and certification process.
Last month, P25 celebrated the 25th year since the initial conference that launched the future of public safety communications technology. Even in 1989, it was obvious the inevitable transition from analog to digital had started and without some serious coordination (through standards), digital radio interoperability would be impossible. The seminal conference in 1989 set us on the path to what we now call P25, or Association of Public-Safety Communications Officials (APCO) Project 25.