In the U.S., Part 15 is an often-quoted section of Federal Communications Commission (FCC) rules and regulations, regarding unlicensed transmissions. It is a part of CFR Title 45 of the Code of Federal Regulations (CFR)., and regulates everything from spurious emissions to unlicensed broadcasting.

Unlicensed broadcasting

Unlicensed broadcasts on the FM broadcast band are limited to a signal strength of 250µV/m² at a distance of 3m from the antenna.

Unlicensed broadcasts on the AM broadcast band are also limited to a signal strength of 250µV/m² at a distance of 3m, however this may instead be measured from the edge of a campus in order to allow for a college radio station to operate.

Unlicensed broadcasts on the TV broadcast bands are prohibited, except for certain medical telemetry devices. 87.5 to 88.0MHz is considered part of the VHF TV band (channel 6), though it shows up on most FM tuners.

Wireless devices in ISM bands

Unlicensed bands at 900MHz, 2.4GHz (2400~2483MHz), and 5.8GHz were originally considered to be used only for industrial, scientific, and medical (ISM) purposes, however the general lack of use of these bands has led the FCC to allow their use for cordless phones, and now for wireless networking, including Wi-Fi and Bluetooth.

Spurious emissions

Electronic equipment from computers to intentional transmitters can produce unwanted radio signals and are subject to FCC regulation. For digital devices including computers and peripherals, FCC Class B is the more stringent standard, applying to equipment marketed for use in the home, even if it could be used elsewhere. Home users are likely to by annoyed by interference to TV and radio reception. Class A is a looser standard for equipment intended only for business, industrial and commercial settings.

Transmitters also must adhere to a spectral mask, to prevent adjacent channel interference, intermediate frequency interference, and intermodulation.

See also:

Family Radio Service CB radio TEMPEST

External links:

FCC Part 15 Rules (http://www.fcc.gov/oet/info/rules/)