FCC Part 15 Radiated Emission (RE) Limits
FCC Section 15.109 – Radiated Limits
Quick reference for FCC Part 15 limits (Section 15.109 Radiated Emissions). View Class A (10m) and Class B (3m) digital device field strength limits in μV/m and dBµV/m.
Class B (3m distance)
Class A (10m distance)
FCC Part 15 Radiated Emission Overview
FCC Part 15.109 specifies the radiated emission limits for unintentional radiators. These limits are designed to prevent electromagnetic interference with licensed communications services.
Measurement Distance: The limits for Class B devices are typically specified at a measuring distance of 3 meters. The limits for Class A devices are typically specified at a measuring distance of 10 meters. If measurements are made at a different distance, an extrapolation factor (typically 20 dB/decade) must be used. You can use our Distance Extrapolation Calculator for quick conversions.
Calculations: The standard specifies field strength in microvolts per meter (μV/m). For engineering convenience, this page also provides the values converted to decibel microvolts per meter (dBµV/m) using the formula: dBµV/m = 20 * log10(μV/m).
How to read this FCC Part 15 reference
User task
Use this page to compare a radiated field-strength result from an unintentional radiator with the Class B 3 m or Class A 10 m limits in 47 CFR § 15.109. The two distance conditions are kept visible because the same numeric field-strength unit does not make the measurement geometries interchangeable.
Choose before comparing
Identify the device class and the prescribed measurement distance before reading a margin. Confirm the frequency band, detector and measurement provisions referenced by § 15.33 and § 15.35; an alternative distance or a carrier-current exception must be justified by the rule text rather than by a generic 20 dB/decade assumption.
What the displayed rows mean
- Class B, § 15.109(a)
- The table is referenced at 3 m: 100, 150, 200 and 500 µV/m for 30–88, 88–216, 216–960 and above 960 MHz, respectively.
- Class A, § 15.109(b)
- The table is referenced at 10 m: 90, 150, 210 and 300 µV/m for the same frequency bands; the dBµV/m column is a logarithmic display conversion.
- Band edges and scope
- At a frequency boundary, use the tighter limit. Below 30 MHz, carrier-current and other special cases can point to different paragraphs, so the 30 MHz-and-above rows are not a universal low-frequency rule.
Common misread
Do not compare a 3 m Class B result directly with the 10 m Class A row, and do not convert distance without checking the applicable FCC measurement method. The page’s µV/m-to-dBµV/m values are unit conversions, not extra limits.
Reference boundary
EMCCalc presents the cited field-strength rows for engineering reference. It does not replace § 15.109, the applicable detector and test procedure, or a formal equipment-authorization assessment.
Content review date:
Need to convert units for this standard?
Try our free RF 50Ω Calculator and Voltage Converter. Instantly convert between dBµV, dBm, V/m, and more.
Source and verification
- Primary source
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Electronic Code of Federal Regulations — 47 CFR § 15.109 Subpart B, § 15.109 (Radiated emission limits)
- Applicability
- Unintentional radiators / digital devices; Class A and Class B limits are shown separately.
- Read this limit with
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- 30 MHz and above
- Class B: 3 m; Class A: 10 m
- Field strength in µV/m and dBµV/m
- Measurement procedure and any alternative distance must follow the rule text
- Last source-link and context review
- Verification method
- The source link, edition/section locator, and measurement context were reviewed against the values shown here. This reference is not a formal conformity assessment or certification.
Engineering reading
Choose the correct equipment class, port, detector, frequency range, facility, and distance before comparing a measurement to a limit.