Radio Spectrum Fact Sheet
In this fact sheet you will find:
Key Points About Radio Spectrum
- Radio communications use radio waves at different frequencies, grouped within bands, that are part of the radio spectrum.
- The Federal Communications Commission (FCC) regulates use of the non-Federal spectrum, including that used by State and local public safety agencies.
- The spectrum is an increasingly scarce resource, and public safety competes with commercial interests for this resource.
- Most recent spectrum allocations intended to help meet increasing public safety spectrum demand include parts of the 700 MHz and 4.9 GHz bands.
- Narrowband channel migration will increase efficient use of the current frequency allocations.
Radio waves are the basic building block of radio communications. Like waves on a pond, a radio wave is a series of repeating peaks and valleys. The entire pattern of a wave, before it repeats itself, is called a cycle. The number of cycles, or times that a wave repeats in a second, is called frequency. Frequency is measured in the unit hertz (Hz), referring to a number of cycles per second. One thousand hertz is referred to as a kilohertz (kHz), 1 million hertz as a megahertz (MHz), and 1 billion hertz as a gigahertz (GHz).
The complete range of frequencies from approximately 30 kHz up to more than 300 GHz that can be used for radio communications. Frequencies are often grouped in ranges called bands. Bands of interest to public safety include HF (high frequency), VHF (very high frequency), UHF (ultra high frequency), and most recently SHF (super high frequency). Radio systems operating in the 806–824 MHz and 851–869 MHz portion of the UHF band are often referred to as “800 MHz systems” and are distinguished from systems in the other parts of the UHF band. Frequencies above 1 GHz are often referred to as “microwave” bands. A radio wave is generated by a transmitter and then detected by a receiver. An antenna allows a radio transmitter to send energy into space and a receiver to pick up energy from space. Transmitters and receivers are typically designed to operate over a limited range of frequencies within a specific frequency band (or bands).
Spectrum allocations for State and local public safety are fragmented into many distinct slices of the radio spectrum. Regulation of specific frequencies for Federal agency use occurs within the National Telecommunications and Information Administration, while the FCC regulates the spectrum for non-Federal users.
The aggregate amount of State and local public safety spectrum allocated within these bands is about 97 MHz and is subject to change pending resolution of re-banding issues in the 800 MHz band. Twenty-four MHz of the TV spectrum (channels 60-69 in the 700 MHz band) has been reallocated to Public Safety. Most agencies do not have access to this band until their regional frequency plans are approved by the FCC, and after local TV broadcasters relinquish these frequencies to Public Safety in 2009. An additional 50 MHz is also allocated for public safety broadband data applications in the 4.9 GHz band. Regional frequency planning is underway, standards are being developed , and manufacturers are gearing up to produce equipment to operate in this new frequency band.
The FCC grants licenses for groupings of frequencies called channels. When the FCC licenses a channel, it authorizes a center frequency (or carrier frequency) and a maximum excursion from that frequency. Radio information is typically transmitted using frequencies contained within a single channel; older public safety radio systems typically use wideband 25 kHz channels.
The FCC has issued an order requiring all public safety agencies to migrate their operating systems below 512 MHz to systems based on 12.5 kHz narrowband channels by 2013. The FCC’s order will affect planning, new equipment purchases, and new systems procured in the timeframe leading up to that date. To avoid interference between systems using the same or adjacent frequencies, the FCC ensures that a channel is licensed to only one user in a given area. As part of FCC licensing, an agency must first confirm availability of specific frequencies from an FCC-authorized public safety frequency coordinator, a private entity that will confirm availability and provide assistance when evaluating frequency design issues.
Notes and Works Cited
 NPSTC, APCO, and other public safety organizations are working toward establishing both technical (TIA 8.8) and operational standards for the 4.9 GHz band. For more information, see http://www.tiaonline.org/standards/procedures/manuals/scope.cfm and www.npstc.org. Back to the text.