The FCC limits spurious emissions primarily through 47 CFR Part 15, which sets field-strength ceilings for consumer radio frequency devices, and 47 CFR Part 97, which sets attenuation requirements for licensed amateur transmitters. Part 15 devices must keep radiated spurious energy below limits that vary by frequency (for example, 100 microvolts per meter at 3 meters between 30 and 88 MHz, rising to 500 microvolts per meter at 3 meters above 960 MHz), and any spurious energy landing in the restricted safety bands listed in 47 CFR 15.205 must stay below those same general limits. Amateur transmitters installed after January 1, 2003 must suppress spurious emissions at least 43 dB below the fundamental signal below 30 MHz, and at least 60 dB below the fundamental between 30 and 225 MHz. Every regulated device must demonstrate compliance through laboratory measurement before it can be sold, leased, or advertised in the United States.
What Counts as a Spurious Emission
When a transmitter or digital circuit operates at a given frequency, it inevitably produces some energy at other frequencies. Spurious emissions are the unwanted signals that fall outside the bandwidth the device actually needs. They differ from out-of-band emissions, which sit close to the intended channel and stem from the modulation process itself. Spurious emissions tend to appear much farther from the carrier and serve no useful purpose.
The most common type is a harmonic, which shows up at whole-number multiples of the carrier frequency. A device transmitting at 150 MHz will produce some energy at 300 MHz, at 450 MHz, and so on. Intermodulation products are another culprit: when two or more signals mix inside a circuit, they create new frequencies neither signal intended. Parasitic oscillations round out the usual suspects, arising from stray capacitance or inductance in the physical hardware. Any of these can land on frequencies used by air traffic control, marine distress channels, or GPS if the device design fails to suppress them.
Spurious energy escapes a device in two ways, and the FCC regulates each separately. Radiated emissions travel through the air from the device’s circuitry or cabling. Conducted emissions travel back through the power cord into the AC wiring, potentially carrying interference through a building. Conducted limits apply from 150 kHz to 30 MHz and are measured at the device’s power terminals using a standardized line impedance stabilization network.1eCFR. 47 CFR 15.107 – Conducted Limits Radiated limits cover frequencies above 30 MHz and are measured at a specified distance from the device. A product must meet both before it can be authorized.
Part 15 Limits for Consumer and Commercial Devices
The core rules for consumer radio frequency devices live in 47 CFR Part 15, which covers intentional radiators such as Wi-Fi routers and Bluetooth speakers and unintentional radiators such as computers and switching power supplies.2eCFR. 47 CFR Part 15 – Radio Frequency Devices Every Part 15 device operates under two non-negotiable conditions: it must not cause harmful interference to any authorized radio service, and it must accept any interference it receives, even if that interference degrades its own performance.3eCFR. 47 CFR 15.5 – General Conditions of Operation If the FCC directs you to stop operating a device because it is causing interference, you must comply until the problem is fixed.
For general radiated emissions from intentional radiators, the FCC sets field-strength limits that vary by frequency band. Between 30 and 88 MHz the ceiling is 100 microvolts per meter measured at 3 meters. Above 960 MHz the ceiling rises to 500 microvolts per meter at 3 meters.4eCFR. 47 CFR 15.209 – Radiated Emission Limits, General Requirements These correspond to very low power levels, enough to keep a garage-door opener from jamming a nearby radio station.
The FCC also draws a line between devices intended for commercial or industrial environments (Class A) and those marketed for residential use (Class B). Class B limits are tighter because homes pack more electronics into closer quarters and consumers generally cannot diagnose interference. Personal computers, tablets, and consumer electronics fall into Class B. Industrial control systems and commercial test equipment typically qualify as Class A.2eCFR. 47 CFR Part 15 – Radio Frequency Devices A manufacturer can voluntarily certify a commercial device to the stricter Class B limits, and the FCC encourages that practice because it reduces interference in the field.
Devices Exempt From the Technical Standards
Not every digital device has to meet the specific Part 15 technical limits. Under 47 CFR 15.103, several categories are exempt, though they still owe the general no-interference obligations and must stop operating on FCC direction.5eCFR. 47 CFR 15.103 – Exempted Devices The exempt categories include digital electronics used exclusively in motor vehicles or aircraft; industrial or utility plant control systems; industrial, commercial, or medical test equipment; digital circuits inside appliances such as microwave ovens, dishwashers, and clothes dryers; medical devices used under a licensed practitioner’s supervision (retail health gadgets do not qualify); any digital device consuming 6 nanowatts or less; and simple peripherals like joysticks and mice containing only non-digital or basic conversion circuitry.
One catch trips up manufacturers regularly: if a piece of equipment contains multiple digital devices, every device inside must independently qualify. One non-exempt component disqualifies the entire unit.5eCFR. 47 CFR 15.103 – Exempted Devices
Restricted Bands Where Only Spurious Emissions Are Allowed
Certain frequency bands are reserved for safety-of-life services, radio astronomy, and other critical uses. The FCC lists these in 47 CFR 15.205, and within them no intentional fundamental transmission is permitted at all, regardless of power. Only spurious emissions may appear, and they must stay below the general field-strength limits in 47 CFR 15.209.6eCFR. 47 CFR 15.205 – Restricted Bands of Operation
The restricted bands include segments used by aeronautical navigation (108–121.94 MHz), maritime distress (156.7–156.9 MHz), GPS (1559–1610 MHz), and radio astronomy (1660–1710 MHz), among dozens of others. This is where emission control becomes genuinely safety-critical, because unchecked spurious energy in these bands could disrupt aircraft navigation or search-and-rescue communications.
Amateur Radio: Attenuation Below the Fundamental
Licensed amateur operators follow a separate rulebook under 47 CFR Part 97. Amateur transmitters can run up to 1,500 watts peak envelope power, so the FCC states the spurious limits as attenuation below the fundamental signal rather than absolute field strength.7eCFR. 47 CFR Part 97 – Amateur Radio Service For transmitters operating below 30 MHz and installed after January 1, 2003, spurious emissions must be at least 43 dB below the fundamental. Between 30 and 225 MHz the requirement jumps to 60 dB below the fundamental.8eCFR. 47 CFR 97.307 – Emission Standards A 43 dB reduction means the spurious signal carries roughly 1/20,000th the power of the intended one, which is demanding even at high station output.
How a Device Proves It Meets the Limits
Compliance is established through measurement, not calculation. For devices that require full certification, testing must be performed at an FCC-recognized accredited laboratory. The lab needs accreditation under ISO/IEC 17025 and must hold the appropriate scope covering the device’s frequency range and test methods.9Federal Communications Commission. Testing Laboratory Qualifications The FCC maintains a list of recognized labs; results from a lab not on the list will not be accepted. For devices that qualify for the lighter Supplier’s Declaration of Conformity path, an FCC-recognized accredited lab is not strictly required, but the testing facility must still maintain a documented description of its test setup as required by 47 CFR 2.948.
From there, the FCC offers two authorization paths, and the right one depends on whether the device contains a radio transmitter.
Certification Through a TCB
Any device with an intentional radio transmitter, including Wi-Fi modules, Bluetooth chips, cellular radios, and remote control transmitters, must go through certification. The manufacturer files its application and test reports with a Telecommunications Certification Body, a private organization accredited to review applications and issue grants on the FCC’s behalf.10Federal Communications Commission. Equipment Authorization The filing goes through the FCC’s Equipment Authorization Electronic System, where the TCB uploads the supporting documentation and, once satisfied, issues the grant of certification in the FCC database.
Costs depend heavily on complexity. A basic digital device with no transmitter may run a few thousand dollars for testing and TCB review. An unlicensed wireless device using Wi-Fi or Bluetooth can cost $9,000 to $12,000 or more once testing and certification fees are combined. Licensed devices with custom radio modules can push past $15,000. These are commercial lab and TCB fees, not government filing fees. A straightforward application typically clears in a few weeks, but design problems uncovered during testing or incomplete documentation can add months.
Supplier’s Declaration of Conformity
Devices that contain only digital circuitry and no radio transmitter can use the Supplier’s Declaration of Conformity path. Under this procedure, the responsible party (who must be located in the United States) self-certifies that the equipment meets all applicable technical standards. No application to a TCB or the FCC is required, and the device does not appear in the FCC’s equipment database.11Federal Communications Commission. Equipment Authorization Procedures Computer peripherals, microwave ovens, LED bulbs, switching power supplies, and radio receivers are common SDoC-eligible products. The responsible party still needs a test report ready and must produce it to the FCC on request. Combination devices such as laptops and tablets, which contain both digital circuits and wireless transmitters, need certification for the transmitter portion even where the digital circuitry would otherwise qualify for SDoC.
What Happens if You Miss the Limits
You cannot sell, lease, advertise for sale, import for sale, or distribute any radio frequency device that has not received its equipment authorization.12eCFR. 47 CFR 2.803 – Marketing of Radio Frequency Devices Prior to Equipment Authorization The definition of marketing is broad enough to reach most commercial activity short of pure research and development.
Enforcement typically begins with an investigation, often prompted by interference complaints or market surveillance. The Enforcement Bureau may issue a Letter of Inquiry requesting information about specific models. If violations are found, the Commission issues a Notice of Apparent Liability proposing a forfeiture and giving the company 30 days to pay or seek reduction.
The base forfeiture for marketing unauthorized equipment is $7,000 per violation, adjusted upward or downward based on factors like willfulness, actual interference caused, compliance history, and ability to pay. The statutory ceiling for most equipment violations outside the broadcast and common-carrier categories is $25,132 per violation or per day of a continuing violation, with a maximum of $188,491 for a single act or failure to act. These figures are adjusted annually for inflation. Manufacturers or service providers that violate accessibility requirements under sections 255, 716, or 718 of the Communications Act face a higher ceiling: up to $144,329 per violation and $1,443,275 for a continuing violation.13eCFR. 47 CFR 1.80 – Forfeiture Proceedings
Beyond fines, the FCC can order product recalls, issue cease-and-desist orders halting sales, and revoke equipment authorizations outright. In egregious cases the matter can be referred for litigation in federal court. Losing an authorization does not just affect one product; it signals to TCBs and the market that a company’s compliance program has failed, making future certifications harder and more expensive.