Part 15 (FCC rules)
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In the U.S., Part 15 is an often-quoted section of Federal Communications Commission (FCC) rules and regulations, mainly regarding unlicensed transmissions. It is a part of CFR Title 47 of the Code of Federal Regulations (CFR), and regulates everything from spurious emissions to unlicensed low-power broadcasting. It is cited as 47 CFR §15.
Contents |
[edit] Subparts
[edit] A - General
Subpart A includes 21 sections from 15.1 to 15.38
[edit] B - Unintentional radiators
Subpart B deals with unintentional radiators --- devices that are not designed to produce radio waves, but do anyway, such as computers. There are 16 sections between 15.101 and 15.123.
[edit] C - Intentional radiators
Subpart C deals with devices that are specifically designed to produce coherent radio waves, such as small transmitters. Specific to broadcasting, 15.239 deals with the FM band, while 15.221 (and 15.219) deal with the AM band.
[edit] D - Unlicensed PCS devices
Sections 15.301 to 15.323 deal with unlicensed PCS devices from 1910 to 1930 and 2390 to 2400 MHz.
[edit] E - Unlicensed NII devices
15.401 to 15.407 deal with unlicensed National Information Infrastructure (U-NII) devices.
[edit] F - Ultra-wideband operation
15.501 to 15.525 deal with ultra-wideband (UWB) devices, including ground-penetrating radar.
[edit] G - Access Broadband over Power Line
15.601 to 15.615 deal with Access Broadband over Power Lines (BPL) devices operating in the 1.705-80 MHz band over medium or low voltage lines.
[edit] Subjects
[edit] Unintentional radiators
Unintentional radiators are designated into two major classes Further Info
- Class A Intended for use in Industrial/Commercial enviornments
- Class B Intended for use in (or adjacent to) Residential/Small Office environments
[edit] Unlicensed broadcasting
Unlicensed broadcasts on the FM broadcast band are limited to a signal strength of 250 µV/m at a distance of 3 meters from the antenna.
The FM broadcast band is limited but not restricted to 87.6 MHz (but see note below on TV) to 107.9 MHz. Any unlicensed broadcasting over a signal strength of 250 µV/m at a distance of 3 m from the antenna is punishable by law and confiscation of all broadcast equipment.
Unlicensed broadcasts on the TV broadcast bands are prohibited, except for certain medical telemetry devices. 87.5 to 88.0 MHz is considered part of the VHF TV band (channel 6 audio is on 87.75), though it shows up on most FM tuners. For TV, 15.241 and 15.242 deal with high VHF (channels 7 to 13), 15.242 also deals with UHF.
On the standard AM broadcast band transmission is limited to 100 milliwatts of power (with restrictions on size, height and type of antenna) or, alternatively, under 15.221, if the AM tranmission originates on the campus of an educational institution, the transmission can theoretically be any power so long as it does not exceed the field strength limits stated in 15.209 at the perimeter of the campus, 24000/F(kHz) µV/m.
[edit] Common uses of Part 15 transmitters
Frequently encountered types of "Part 15" transmitters include:
- Low-power broadcasting, often by hobbyists, or on college or high school campuses.
- Small FM radio transmitters designed to hook to the audio output of an iPod or other portable audio device and broadcast the audio so that it can be heard through a car audio system that is not equipped with an audio input.
- Very low power transmitters, often referred to as "talking roadsign", "talking houses" or "talking billboards", which will air a repeating loop of highway construction, traffic, promotional or advertising information. A sign placed near the transmitter is used to entice passersby (nearly always in automobiles) to tune in. The talking house gets its name from the fact that many such transmitters are installed at houses that are up for sale, thus enabling a passerby to find out details about the interior of the house without actually touring the building. Many talking houses have been noted by DXers apparently using unauthorized power levels and antenna systems, and thus audible far beyond the limitations authorized under Part 15. In the northwestern US, Oregon Department of Transportation and the Washington State Department of Transportation frequently set up such systems near road construction worksites to inform drivers of expected delays and detours, duration and history of the construction project drivers are passing.
- Wireless microphones and headsets, which broadcast the speakers voice to a receiver which amplifies the audio. Wireless mics allow the speaker to move about freely, unlike a conventional microphone, and are thus popular with musicians.
- Toys such as the popular late-1970s toy Mr. Microphone and its imitators, which would broadcast the user's voice to a nearby AM radio. Variations on this type of transmitter were advertised for sale in radio magazines as far back as the 1920s.
- Walkie Talkies intended for children's use, baby monitors, and some older cordless phones all operate on frequencies in the 49 MHz band (or rarely at the upper end of the AM broadcast band) and have been known to interfere with one another.
[edit] 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 be 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.
