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 TechnologySo, the FCC says all new systems will have to operate on 12.5 kHz channel assignments by 2013. The question is do you switch to analog or digital equipment or equipment capable of doing both, and if digital, WHICH digital standard? So why the rush to digital? Actually it is a combination of factors – regulatory, operational, and budgetary. The FCC rules and regulations force change at mandated times. Currently, those mandates require all manufacturers to produce equipment capable of operating at 6.25 kHz channel spacing by 2011 while users are required to reduce channel spacing to 12.5 kHz by 2013 and to 6.25 kHz by 2018. To compound the issue, Volunteer Fire Departments in Alabama must convert to 12.5 kHz operation by January 1, 2009, four years ahead of the FCC rules (More information available at www.info4u.us/AFD.pdf Does that leave you with questions? You are not alone!
From an operational viewpoint you have a choice of purchasing analog or digital equipment in any one of four different technologies starting with analog only capable of operating at 25 or 12.5 kHz. ICOM and Kenwood have joint ventured to develop the most advanced technology capable of operating a 24, 12.5 or 6.25 kHz with both analog and digital capability. This is technically known as FDMA. ICOM calls it IDAS (ICOM Digital Advanced System) Motorola has a competing technology as MotoTRBO (technically, TDMA), and there is a federal government technology standard known as APCO-25 or simply, P25.
Of the three technologies, only IDAS is currently capable of operating at 6.25 kHz. P25, being the federal standard is in the planning stages at this time to be available in a 6.25 kHz version by 2011. Motorola's 2-slot TDMA apparently meets the intent of the FCC regulator changes even though it cannot operate on a single 6.25 kHz channel. If this sounds like double speak, don't blame us - we'll let Motorola explain it for themselves at www.info4u.us/mototrbowhitepaper.pdf. All three technologies are available in the VHF and UHF frequency bands. P25 is also available in the 700/800 MHz band. Both IDAS and P25 are available with trunking capability and backwards compatibility with analog systems operating at 25 or 12.5 kHz through repeaters.
Although there is no legal requirement to purchase narrow band (12.5 kHz) or ultra narrow band (6.25 kHz) at this time, there are significant operational benefits in the areas of extended battery life on portables, enhanced features such as text messaging and GPS, improved signal clarity, and group/individual calling in complete privacy.
More importantly, reduction of channel spacing (bandwidth) causes a reduction in audio. This equates to a reduction in operating range for the same transmitter power (i.e. a 50 watt analog transmitter operating at 12.5 kHz will not talk as far as a 50 watt transmitter operating at 25 kHz). At 6.25 kHz, analog transmitters don’t work at all! Digital systems are not affected by reduced bandwidth. This gives a huge advantage to digital systems over analog.
From a budgetary viewpoint, digital equipment is more expensive than analog but in the long run an investment today will save you money. Case in point – let’s say you purchase a good quality six hundred dollar analog radio today. Let’s go forward a few years when many users switch to 6.25 kHz. Remember than the “new” 12.5 and 6.25 kHz “channels” are simply the old 25 kHz channels split in half or quartered as applicable.
If you are operating at 12.5 kHz with analog radios, you have already experienced range reduction resulting in the cost of additional repeater stations, higher powered radios or other technology to compensate for lost coverage. Worse yet, digital systems operating at 6.25 kHz can actually share a channel with a 12.5 kHz user. They never hear you, but they can virtually destroy your ability to communicate. The result is that you may have to replace equipment in just a few years. With that thought in mind, digital makes a lot sense since on average, there is only about a 25% difference between comparable cost analog and IDAS or MotoTRBO equipment. P25 is about 50% more, but still an excellent value considering the current equipment is certified for use through 2017!
Should you go digital? We think so! Which technology should you choose? That is the subject for another discussion. We will provide some pointers in the Product Comparisons shown at the top of this web page. In the meantime, if you want a more detailed knowledge on the subject of digital technology, read on.......
Here's the long and the short of what happens when you switch from 25 to 12.5 kHz using analog equipment. Audio will be reduced as noise increases with the reduced bandwidth. Reduced audio means reduced range since reception is a function of being able to HEAR thereceived signal. Digital doesn't have this problem since the data (whether voice, text, or GPS) is treated all the same. Voice is converted into digital bits (remember those zeros and ones you learned about in school?), transmitted over the air and coverted back to analog voice in the receiving radio with no noise and no degradation. Digital radios use a gadget called a vocoder. The vocoder performs a number of functions including the voice conversion from analog to digital and vice versa. From a user viewpoint, a vocoder is simply a voice processor. By processing the voice, what you hear sounds better. Remember the older cellular phones (vintage 1980's). Those were analog. By the late 90's companies like Powertel (now T-Mobile), Sprint, and Nextel were offering digital wireless phones. The difference is voice quality was significant. Today, virtually all celluar phones use digital technology althought many of them are backwards compatible with analog systems operating in rural areas. This is basically what a digital radio does that has backwards compatible capibility. It can communicate in a digital mode, an analog mode, at 25 kHz channel spacing or 12.5 kHz channel spacing. Any radio being purchased today for public safety should have this capability. Once you have a digital compatible radio, you have to choose an operating platform, typically P25, the US standard for federal agencies, 2-Slot TDMA, also known as MotoTRBO, or FDMA, also known as 6.25 and more recently IDAS (ICOM Digital Advanced System) Regardless of which one you select, you will have better audio, typically greater range (due to improved audio quality), privacy (scanners are not yet available to monitor digital 2-way radios), interoperability with both 25 and 12.5 kHz radio systems, either analog or digital, and significantly improved battery operating life (digital radios draw less current than analog radios). Additionally, digital radios are well suited for handling text messages, data, and GPS vehicle tracking.  Most importantly, digital radios are designed for integration with computer networks. This allows computers, radios, and the Internet to operate as a part of a complete system. The benefits to this integrated technology is HUGE! 9/11, Katrina, and other disasters have shown the need for interoperability between different user groups. An integrated digital communications system is the foundation for coordinating fire, EMS, law enforcement, transportation, and support services utilizing a common coordinated network. There are basically four digital technologies currently available for private radio communications system use. They are as follows:
APCO-25 (C4FM and CQPSK)
More commonly known as P25, this is the digital standard selected by U.S. Government agencies and presumed by many to be the platform best suited for all public safety users. The purpose of P25 was and is to provide a common platform offering the highest level of interoperability while simultaneously addressing the need to move to narrow frequency channel spacing. On of the best overviews of P25 has been prepared by Aeroflex, a test equipment manufacturer offering equipment for the servicing of P25 equipment. For additional information, please visit www.p25.com/wpaper.asp. Technically, this is known as C4FM, compatible four-level frequency modulation) in a 12.5 kHz channel or CQPSK, compatible quadrature phase shift keying) in a 6.25 kHz channel. To the best of our knowledge, there is currently no P25 equipment available with 6.25 kHz capability although current FCC rules call for all radios in the USA be compatible with 6.25 kHz by 2011. Major suppliers of 12.5 kHz equipment include BK/Relm, ICOM, Johnson, Kenwood, MA-COM, Midland, Motorola, and Tait. ICOM by far offers the most attractive pricing on mobiles and handheld portables and uniquely offers optional Intrinsically safe operation. P25 offers true backwards compatibility with all the features of analog systems including 2-tone paging. P25 models are available in various configurations and are not necessarily compatible with each other (although that was the supposed original design criteria). P25 radios are available in the VHF, UHF, and 700/800 MHz band but selections in the 700/800 MHz were currently not available from the majority of manufufacturers in the winter of 2007/2008. Unlike MotoTRBO, which must be operated in either an analog or digital mode, all of ICOM's P25 radios can accomodate both analog and digital reception on a single operating channel.
FDMA (4 Level FSK)
FDMA (Technically known as dPMR for Digital Professional Mobile Radio) is a new commercial digital standard jointly developed by ICOM and Kenwood to provide the ability for a radio to function in either a digital or analog mode at 25 kHz, 12.5 kHz, or 6.25 kHz. Technically known as Frequency Division Multiple Access (4 level FSK), it is currently the most flexible and affordable platform available for VHF or UHF systems. ICOM is now offering second generation FDMA technology known as IDAS (Icom Digital Advanced System). With a one year lead over Kenwood, ICOM is by far the more experienced in FDMA. This technology has a significant price advantage over P25 and and is an excellent choice for local and regional area interoperability. ICOM originally offered the F3061 VHF and F4061 UHF series handheld radios as well as mobile, base, and repeater radios either in an analog only version with plug in digital capability when required. The new F3161 VHF and F4161 series portable radios now have the same capabilities as the mobiles and a brand new base/repeater station series will round out the package for ICOM's newest offering - the IDAS ICOM Digital Advanced System). Unlike MotoTRBO, the ICOM IDAS system allows mixed mode analog/digital operation on the same channel and retains the ability to send and receive conventinal 2-tone signalling. Unlike MotoTRBO, which requires repeaters to operate in either an analog or digital mode, ICOM's new F5000 and F6000 series repeaters can accomodate both analog and digital mixed mode operation on a single channel. This system is especially well suited for commercial users and public utilities. We have prepared a complete report on this system at www.info4u.us/dcom.pdf. Check it out. We think you will find the information to be of interest.
FHSS (Frequency Hopping Spread Spectrum)
FHSS is the platform used in the Motorola DTR 900 MHz on site radios. FHSS has been around for a long time. A pioneer developer, Aironet (now a part of Cisco Systems) developed this technology for wireless Access Points and Bridges in the 2.4 GHz band. This has become a defacto standard for today's Wireless Local Areas Networks (LANS) as well as cellular phones operating at 900 MHz, 2.4, and the 5 GHz range. This technology is normally not used by public safety agencies since there is not migration or compatibility capability with exising VHF or UHF radio systems. Additionally, there are no base stations, mobiles, or repeaters. The only current offering in the spring of 2008 is a portable version. Additional information is available at www.dtr2way.com.
TDMA (Time Division Multiple Access)
TDMA (known in Europe as DMR for Digital Mobile Radio) has been around for a long time in the cellular industry although most advanced cellular systems are moving to GSM or advanced CDMA technology. Variations of TDMA are used in the 2-Slot MotoTRBO radios first introduced in 2007. It is also the only product to our knowledge with optional built in GPS. Although capable of operating in both analog and digital mixed modes on different channels (MotoTRBO is not capable of mixed mode opertion), there is no provision for 2-tone paging which can be an issue for fire and rescue users desiring to migrate from analog to digital. Interestingly, Motorola does not advocate the use of MotoTRBO for public safety use. Rather, the featured application is for Professional or Commercial users. Unlike P25 radios, the current repeater stations are not capable of operating in both an analog and digital mode simultaneously. This could be a major deterrent to those that are planning a migration from analog to digital over an extended period of time. The main user benefit of MotoTRBO (at least as we see it) is the ability of a single repeater to provide the functions of TWO repeaters with a single device on a 12.5 kHz channel. Base stations, mobiles, and handheld radios are available at prices comparable to other models in the Motorola Professional Series (EX, HT and PR series). 700/800 MHz models are not available. For more information on MotoTRBO, go to www.falcondirect.com/mototrbo. Summary With the exception of consumer grade radios, there is no reason why any public safety or commercial user should not consider the digital alternative. Not only do you get better channel efficiency (2 or 3 slots per single 25 kHz channel), you get privacy, the ability to communicate with everyone in your work group, a selected work group, or even to an individual. You get both voice and text messaging capability plus optional GPS. Your handheld radio batteries last longer, and you talk farther with digital clarity. The future in communications is digital, and the future is NOW!
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