As of January 1, 2013, the Federal Communications Commission (FCC) has restricted the manufacturing and importation of radio systems that do not utilize certain bandwidth efficiencies. The FCC mandate is referred to as " N arrowbanding." This requires all Part 90 radio systems with operating bandwidths of 150 to 174 MHz and 421 to 512 MHz to either utilize a maximum bandwidth of 12.5 kHz or provide a minimum of one 12.5 kHz voice path channel. Equivalent efficiencies are permitted. This includes 25 kHz channels with two voice paths or data operations with rates greater than 4.8 kbps per 6.25 kHz channel.
The FCC initially set an interim deadline of January 1, 2011, at which time it limited the license applications it would accept as well as what bandwidth certifications it provided. However, it did not yet restrict importing or selling non-compliant equipment. But as of the 2013 deadline, non-compliance is an actionable violation that can result in losing one's license, fines, or official admonishment. This applies equally to government entities, although some paging-only channels are exempt.
Note that Narrowbanding does not require licensees to change frequencies, obtain new channels, or implement new digital technologies. It specifically requires the reduction of bandwidth or use of equivalent efficiencies. Additionally, licenses for 25 kHz channels do not automatically entitle licensees to two separate 12.5 kHz channels, nor will the 25 kHz channel be split into two 12.5 kHz channels. To apply for additional channels, contact your area's certified frequency coordinator. Narrowbanding is also not rebanding, which is a separate process regarding 800 MHz frequencies, nor does it involve "tri-band" radios.
The FCC implemented Narrowbanding because of the limited spectrum available for the implementation or expansion of systems on UHF and VHF frequencies. Most UHF and/or VHF LMR operations were utilizing 25 kHz efficiencies, congesting that spectrum. The mandate streamlines bandwidth and expands voice paths in order to support more licensees within the spectrum. Do note that this may result in some loss of signal strength, about 3 dB; one should consult with manufacturers to determine how any specific system could be affected.
It is also hoped that Narrowbanding will not only engender new technological advances for increased efficiency but also allow the spectrum overall to be less susceptible to breakdown and interference. Communication, data, and infrastructure have become targets in 21st century international disputes and even terrorism. A strong UHF and VHF spectrum will maintain important communication and emergency channels in any emergency. This is a part of the reason why most public safety radio systems remain analog and not digital. The Telecommunications Industry Association and the Association of Public Safety Communications Officials International worked together on a program titled Project 25, which developed a standardized trunked channeling system that accommodates multiple channels and is based on the 12.5 kHz mandate.
Now that the deadline has passed, the FCC has likely terminated the license of any licensees that did not transition to the mandated changes, and re-certification will likely be very difficult. The FCC made the Narrowbanding mandate in 1992 as a part of its "refarming" initiative and has already permitted an extension from the initial 2011 deadline to the hard deadline of 2013. The FCC also plans to ultimately minimize the utilized bandwidth further to 6.25 kHz. There is a current final channelization plan for the eventual migration, but the FCC has not yet mandated a deadline for this process. The National Public Safety Telecommunications Council is concerned with the interoperability of the public and safety communications paths. Along with the Land Mobile Communications Council, they supported the extension and the firm adherence to the 2013 deadline. Together with the FCC, they are working to plan out the smoothest transition for further bandwidth limitations. This will be referred to as "narrow-narrow band."
Licensees seeking additional information or assistance have a few resources available to them. The International Association of Fire Chiefs and the International Municipal Signal Association are especially helpful for any safety or emergency crews but are also able to redirect questions to more appropriate venues. For other public safety coordinators, visit the FCC website. For licensing issues, situational concerns, or other legal questions, contact Telecommunications Legal Counsel.
The following links also offer helpful information: