Introduction
In the United States, the Federal Communications Commission (FCC) has designated several frequency bands as “unlicensed” bands, where anyone can operate wireless equipment without having to obtain a license from the FCC. The most well-known of these bands are the 2.4 GHz and 5 GHz wireless LAN bands, which are used by WiFi devices. Other unlicensed bands include the 900 MHz band (used by some cordless phones and two-way radios) and the ISM band (used by various industrial, scientific and medical devices).
The FCC has placed some restrictions on unlicensed devices operating in these bands. For example, unlicensed devices in the 900 MHz and ISM bands must not cause interference to licensed users of those bands (such as cellular phone or satellite TV providers). In addition, the FCC has specified maximum power levels and frequency hopping requirements for unlicensed devices operating in the 2.4 GHz and 5 GHz wireless LAN bands. These restrictions are designed to reduce the risk of interference between different types of devices operating in these bands.
The CB Radio Service
The CB Radio Service is a private, two-way, short-distance voice communications service for personal or business use. CB radios are used in the US and many other countries around the world. In the US, CB radios operate on 40 channels in the 11-meter band. The term “CB” comes from the Citizens’ Band radio service, which was created in 1945.
CB radios have a number of features that make them ideal for use in a variety of situations, including:
- emergency communications
- checking in with friends and family
- keeping up with local news and events
- coordination of activities like hiking, camping, and travel
CB radios are relatively simple to use, and no license is required to operate one. Anyone can buy a CB radio and start using it immediately.
The Family Radio Service
The Family Radio Service (FRS) is a two-way personal radio service that is licensed in the United States. FRS radios are limited to half-watt power output and have a maximum range of about two miles. FRS radios are typically handheld portable units, similar in size to a walkie-talkie.
The General Mobile Radio Service (GMRS) is a two-way personal radio service that is licensed in the United States. GMRS radios are limited to five watts power output and have a maximum range of about 20 miles. GMRS radios are typically handheld portable units, similar in size to a walkie-talkie.
The Multi-Use Radio Service (MURS) is a two-way personal and business radio service that is unlicensed in the United States. MURS radios are limited to two watts power output and have a maximum range of about four miles. MURS radios are typically base station units, mobile units, or handheld portable units.
The Citizens Band Radio Service (CBRS) is a two-way personal and business radio service that is unlicensed in the United States. CBRS radios are limited to five watts power output and have a maximum range of about three miles. CBRS radios are typically mobile units or handheld portable units.
The General Mobile Radio Service
The General Mobile Radio Service (GMRS) is a land-mobile FM UHF radio service designed for short-distance two-way communication. It requires a license in the United States, but some GMRS transceivers are available as dual-service units with FRS on board as well. channels 1 through 7 of the GMRS band are shared with the 22 channels of the FRS. The maximum power output allowed on the shared FRS/GMRS channels is 0.5 watts (50 milliwatts). The power limit on all other GMRS only channels is 50 watts
The FCC first released rules for the GMRS in 1959 as a short-range walkie-talkie service, intended to be used for activities such as camping and hiking trips, neighborhood and family get-togethers, and small conventions and meetings. In early 2000, new FCC rules went into effect that expanded the service by allowing repeater use and increasing the maximum transmitting power to 50 watts
The Multi-Use Radio Service
The Multi-Use Radio Service (MURS) is a license-free radio service that does not require a permit for operation in the United States. The MURS spectrum consists of five frequencies: 151.820, 151.880, 151.940, 154.570, and 154.600 MHz. All MURS devices must be type-accepted by the Federal Communications Commission (FCC) in order to operate in the United States.
MURS is intended for short-distance communications and offers an alternative to the Family Radio Service (FRS), which has become congested in some areas due to its popularity. MURS radios are typically handheld transceivers with a maximum power output of 2 watts, though some base station radios are available with up to 5 watts of power. The maximum permissible antenna height for MURS radios is 20 feet above ground level (AGL).
MURS channels are referred to by number rather than frequency, and each channel occupies a bandwidth of 12.5 kHz. Channels 1 and 2 are simplex (one-way) only, while channels 3-5 support both simplex and duplex (two-way) operations. channel 1:151.820 MHz; channel 2:151.880 MHz; channel 3:151.940 MHz; channel 4:154.570 MHz; channel 5:154.600 MHz
The Personal Radio Service
The Personal Radio Service is a set of unlicensed rules for low-power two-way radios, wirelessly interconnected devices, voice pagers, and digital Champagne chat systems. These devices operate in various frequency bands between 155 and 28 MHz. Most PRS equipment uses FM modulation; however, some manufacturers offer AM equipment as well.
The Radio Control Radio Service
The Radio Control Radio Service is a service for the control of model aircraft, boats and cars. It uses radio signals in the 72-76 MHz and 27.405-27.5 MHz frequency bands. You do not need a licence to use this service, but you must not cause interference to TV or radio reception, or to any other users of the radio spectrum.
The Citizens Band Radio Service
The Citizens Band Radio Service (CBRS) is a private, two-way, short-distance voice communications service for personal or business use. This service is available in the United States on a shared basis in the 26.96-27.41 MHz range.
The rules for CBRS are found in Title 47 of the Code of Federal Regulations (CFR), part 95. The rules were first established in 1958 and have been amended several times since then, most recently in 2013.
CBRS allows for two types of operation:
-Individuals may operate on a “voice” basis using any type of AM, FM, or single-sideband modulation; and
-Businesses may operate on a “data” basis using any type of modulation at data rates up to 19.6 kilobits per second (kbps).
There are 40 channels in the CBRS band, each with a bandwidth of 30 kHz. Channels 1 through 7 are reserved for emergency communications, and channel 9 is reserved for travelers information broadcasts. The other 32 channels are available for general use.
The unlicensed frequency bands
There are a number of unlicensed frequency bands in the United States that can be used for wireless communications without the need for a license. These bands are typically used for short-range, low-power applications such as WiFi and Bluetooth.
The most common unlicensed frequency bands are:
-2.4 GHz
-5 GHz
-900 MHz
-1.2 GHz
-1.7 GHz