Radio Bands & Frequencies

The scope of this publication is to provide a basic overview of how radio bands and frequencies apply to radio scanning. This section is not meant to be an explanation into how the radio spectrum works, from which radio bands and frequencies result. A technical explanation into how the radio spectrum works would be well beyond the scope of this book. Besides, you do not need to know all that technical mumbo-jumbo to enjoy scanning. If, however, you are interested in learning the technical aspects of how the radio spectrum works, check out the tutorial on how the radio spectrum works from HowStuffWorks.com. 

The information contained on this page is broken down into the following topics:

• The FCC (Federal Communications Commission)

• Radio Frequencies

• Radio Frequency Allocations

• Radio Frequency Bands

Every country has its own rules governing usage. In the US, the FCC is the government agency that handles issues regarding radio transmissions, usage, and licenses for all non-military radio systems. The Wireless Telecommunications Bureau (WTB) is the branch of the FCC that handles nearly all FCC domestic wireless telecommunications programs and policies. To learn more about the wireless communication services, click here.

The National Telecommunications & Information Administration’s (NTIA) Office of Spectrum Management (OSM) is responsible for managing the Federal Government's use of the radio frequency spectrum.

The US Radio Frequency Spectrum Allocation establishes which radio services operate in a given frequency band. There are thirty different radio services in over 450 separate frequency bands.

You can view the US Radio Frequency Allocation Chart (in pdf format) here. The chart graphically partitions the radio frequency spectrum, extending from 9 kHz to 300 GHz, into over 450 frequency bands, and uses distinct colors to distinguish the allocations for the thirty different radio services. For more information, see: Basic Elements of Spectrum Management.

A frequency is a path or "channel" used for communications. It is a spot on a radio band identified by its number. To hear transmissions for what you want to listen to, you must have the specific frequency for that channel programmed into your scanner. For example, my local police department’s (Covina PD, CA) main dispatch frequency is 154.7250 MHz.

In busy/populated areas, police and fire agencies will most likely have several frequencies that they use for daily operations. You will most likely find a separate frequency for dispatch, car-to-car, tactical use, detectives, and so on. My local police department has a secondary frequency for car-to-car/tactical communications. In addition, there is a separate channel for investigators and mutual aid. For fire agencies, you will most likely find a separate frequency for dispatch, response coordination, on-scene "fireground" tactical use, paramedics, and so on.

In trunk radio systems, frequencies are not assigned to a particular use, they are assigned in a "pool"and usage is based on availability. See our trunk radio page for a complete overview of how trunk radio systems utilize frequencies.

Channel Designations

A channel designation is used to identify a frequency by name rather than by number. For example, Channel-1 (dispatch) and Channel-2, Frequency-1 and Frequency-2, or Blue channel, Red channel, Primary and Secondary, etc.

Continuous Tone Coded Squelch System (CTCSS)

CTCSS (Continuous Tone Coded Squelch System) is a system that is used to avoid interference between separate agencies within close proximity to each other using the same frequency. Each radio for a particular agency is programmed with a CTCSS code so that only those radios can hear and talk with each other and not a neighboring agency.

The system involves an industry standard set of sub-audible tones for controlling radios and associated equipment. The sub-audible tone is added to the transmitted signal. The receiving radio is then set up to listen for this specific tone in the received and demodulated audio. If the matching tone is present, the squelch is opened up, allowing the audio to pass through to the speaker. If the tone is not present, then the radio remains silent, even though there is a signal on the frequency. This allows two or more agencies to use the same frequency (generally on a repeater), but not hear each other's conversations.

CTCSS is also called "PL Tone" and is the Motorola Proprietary name for CTCSS. Several other companies have marketed their own brands of CTCSS under different names including "Channel Guard", "Quiet Channel", "Quiet Mode", and "Private Mode".

DCS on the other hand stands for Digitally Controlled Squelch. It is also called DPL or Digital Private Line and Digital Channel Guard. DCS is a digital code that is sent to open the squelch just like the tone does in CTCSS.

Some newer high-end scanners come with a CTCSS DCS/PL decoder built in it. If an agency is the only user in the area, there's no need to worry about a PL tone to filter out other users. There are advantages however, like in busy metropolitan areas where CTCSS helps keep a lot of unwanted junk out of your speaker. Without CTCSS or DCS, your scanner will pick up a lot of unwanted stuff you just don't want to hear. On the flip side, I live in eastern Los Angeles County where many public safety agencies reside and have never experienced problems without CTCSS capability. For a more detailed explanation of CTCSS/PL & DPL Tone Codes, see the Delaware Repeater Association’s article: CTCSS, PL, Tone Squelch, and Other Necessary Evils.

Land Mobile Radio Service (LMRS)

Previously there were twenty radio categories allocated for land-mobile usage divided into the four main service groups below. This radio service allocation system was known as the Land Mobile Radio Service (LMRS) and was divided in the following manner:

• Police
• Fire/Paramedic
• Forestry
• Conservation
• Highway Maintenance
• Local Government
• Emergency Medical
• Special Emergency

• Business
• Special Industrial
• Forest Products
• Petroleum
• Telephone Maintenance
• Film and Video Production

• Power & Utilities
• Manufacturing Companies
• Relay Press

• Motor Carrier
• Railroad
• Taxicab

FCC Frequency Usage Reallocation

The FCC is has been and is currently "re-farming" or restructuring the land-mobile frequency categories. Under this new allocation system, the main categories above have been combined and/or expanded into two major categories, the Public Safety Radio Pool and the Industrial/Business Radio Pool.

The Public Safety Radio Pool covers the licensing of radio communications of state and local governmental & municipal entities. This new setup expands the previous system to include more activities:

• Police & fire service
• Medical services
• Rescue organizations
• Veterinarians
• Assisting persons with disabilities
• Disaster relief organizations
• School buses
• Beach patrols
• Establishments in isolated places
• Communications standby facilities
• Emergency repair of public communications facilities

The Industrial/Business Radio Pool is composed of frequencies that were previously allotted to any of the Industrial, Land Transportation, or Business Radio Service. The Industrial/Business Radio Pool covers the licensing of the radio communications for entities engaged in the following commercial activities:

• Clergy or religious institutions
• The operation of educational, philanthropic, or ecclesiastical institutions
• The operation of hospitals, clinics, & medical associations
• Manufacturing and public transportation

Frequency bands are divided into a range of frequencies called "frequency bands". The following list contains some common radio frequency bands for monitoring. A complete listing of FCC Frequency Band Allocations can be found here.

Common Radio Bands for Monitoring:

* MHz – Megahertz

Note: Not all scanners can receive all the bands above.