Anyone applying for a land mobile radio license knows the difficulty in finding available spectrum. Since 1991, the FCC has attempted to foster more efficient use of the most heavily used Part 90 frequencies (150 MHz and 450 MHz bands). In doing so, the commission initially encouraged migration to more spectrum-efficient systems through the equipment-certification process.

When this tactic proved unsuccessful, the FCC mandated conversion to narrowband equipment or equivalent technologies and imposed a Jan. 1, 2013, deadline for all licensees to migrate to 12.5 kHz bandwidth or equipment of equivalent efficiency.

The FCC also required radio manufacturers as of Jan. 1, 2005, to submit only new radios capable of either (1) operating on 6.25 kHz channels or (2) meeting a narrowband efficiency standard, e.g., one channel (voice) or 4800 b/s (data) per 6.25 kHz channel. The commission also had created 6.25 kHz channels interspersed between the original 25 kHz channels (at 450 MHz) and the original “offset” channels. VHF channels also were available in 7.5 kHz channel bandwidths; however, no radios existed to operate on any of these channels.

Late last year, some manufacturers asked the commission to eliminate the radio-certification requirement. They felt it placed burdens on manufacturers and could jeopardize interoperability. As a result, the FCC stayed the rule and asked the industry to comment by Aug. 15.

In response to this challenge, manufacturers developed 6.25 kHz FDMA digital radios capable of operating on both 6.25 kHz UHF channels and 7.5 kHz VHF channels. Engineered from existing FM radio hardware, the equipment not only meets the FCC's efficiency standards but also is no more expensive than today's best-quality units, resulting in affordable deployment by users.

Interoperability with other manufacturers' devices becomes possible when all vendors support the development of a common air interface. However, interoperability with legacy equipment is easy because these digital radios are backward-compatible, i.e., a user with the 6.25 kHz FDMA radio can communicate with analog radios. Also, mixed analog and digital radios can be used on the same channel or systems, with some channels on the radio set to 6.25 kHz and some to 12.5 kHz. System upgrades can be made over time, a big plus for enterprises wishing to avoid a wholesale replacement and the resulting loss of their investment in perfectly usable equipment.

Current licensees can increase their capacity on existing channels. Depending on channel center, a 12.5 kHz UHF channel licensee can implement two 6.25 kHz channels without causing interference to adjacent channels. On 150 MHz Part 22 channels and 470 MHz Part 90 channels, a licensee with three contiguous frequencies can divide them into 11 6.25 kHz channel slots. Digital radios engineered to monitor co-channel and offset channel communications will disable transmission until the channel is clear for operation in a co-channel situation. The result is that available spectrum has been “created” for the digital radio user.

In his best-selling book “The Innovator's Dilemma,” Clayton M. Christensen argued that waiting for technology to catch up with consumer demand can be the downfall of even highly successful companies. He reports that it's the hungry innovators who wind up finding solutions and grabbing market share. “As in many of life's most challenging endeavors, there is great value in coming to grips with ‘the way the world works,’ and in managing innovative efforts in ways that accommodate such forces,” he wrote.

In reality, the old way of using frequencies is finished. It's up to us as communication companies to embrace the innovative solutions that move us and our customers forward.


Chris Lougee is vice president at Icom America and leads its land mobile radio division. A member of the Icom America team for 15 years, he heads a sales staff of more than 70 Icom-employed and -contracted sales representatives. Most -recently, Chris spearheaded the development of Icom America Systems (IAS), a turnkey radio systems solution provider.