In 1992 the FCC adopted the forthcoming narrow banding requirements known as “refarming”. The basic purpose of this action was to enhance spectrum efficiency in the VHF and UHF land mobile bands. Narrowbanding should not be confused with 800 MHz rebanding.
Narrow banding will allow the spectrum a better use of the frequencies already in place by reducing the existing 25 KHz channels to 12.5 KHz splits. Any equipment that is not capable of operating on channels of 12.5 KHz or less will need to be replaced.
Migration to 12.5 kHz efficiency technology (once referred to as Refarming, but now referred to as Narrowbanding) will allow the creation of additional channel capacity within the same radio spectrum, and support more users. The emergency response community is running out of channels in the VHF and UHF bands. The FCC plans to redistribute (refarm) newly created channels to help new emergency responder agencies obtain channels and enable existing agencies to expand.
After 15 years, numerous Petitions for Reconsideration and other challenges, the final FCC plan was decreed by the Commission early in 2007, with the setting of firm dates for the transition.
The FCC rule applies to both conventional and trunked radio systems and affects all FCC-licensed State and local emergency response radio systems. Transitioning to narrowband radio can make some portable, mobile, paging, base-station and repeater radios obsolete, resulting in a loss of coverage or capacity.
Since January 1 2011, The FCC no longer accepts applications for modification of VHF or UHF systems that operate on wideband channels (25 KHz). All new applications must have a maximum bandwidth of 12.5 kHz; no further modifications to existing wideband licenses.
01/01/2013 – All current licensees must be fully operational on 12.5 kHz equipment. After January 1, 2013, all 150-174 MHz or 421-512 MHz band equipment manufactured, imported, or certified in the United States must be capable of super-narrowband transmissions (6.25 kHz)
VHF land mobile narrowband uses 7.5 kHz spacing. Existing VHF channels will remain, with new ones. While in the UHF band, along with existing channels will exist low-power offset channels. Between these frequencies new channels will be created with 6.25 kHz spacing.
Radio equipment manufacturers have been aware of the pending narrowband mandate since 1997 and most of the equipment purchased in the last five years will be capable of changing to narrowband operation simply by reprogramming. But buyers of new radios and scanners should check to determine whether they can tune to the new channels or not.