Most clients inquire about specific test items for FCC SDoC. The general answer is FCC Part 15B, but it is essential to learn detailed test ranges, limits and differences between Class A and Class B.

1. Applicable Standards for FCC SDoC

FCC SDoC testing is governed by 47 CFR FCC Part 15 Subpart B, which regulates non-intentional radiators — electronic devices that do not actively transmit radio signals but generate electromagnetic interference during operation.

Other subparts under Part 15 are not applicable to SDoC: Subpart C for intentional radiators (wireless products for FCC ID), Subpart E for U-NII devices and Subpart F for ultra-wideband devices.

The test method follows ANSI C63.4-2020, the current official standard for test environment setup, parameter configuration and data recording. All official reports cite FCC Part 15 Subpart B and ANSI C63.4-2020.

  2. Core Test Items: Conducted Emission & Radiated Emission

--Conducted Emission

-This test measures electromagnetic interference transmitted through AC power lines, which may disrupt other devices on the same power grid.

-Frequency range: 150 kHz to 30 MHz.

-Exemption rule: Battery-only devices without AC input are exempted. Products supporting both battery and external adapter power must complete this test.

-Test setup: Conducted emission is tested via Line Impedance Stabilization Network (LISN). Both quasi-peak and average detection values must meet the limits.

-Limits classification: Two categories based on usage environment:

·Class B (Residential/Office Use): Stricter limits for consumer products.

·Class A (Industrial Use): Looser limits for commercial and industrial equipment.

Class B Conducted Emission Limits

·150 kHz ~ 500 kHz: Quasi-peak 66~56 dBμV, Average 56~46 dBμV

·500 kHz ~ 5 MHz: Quasi-peak 56 dBμV, Average 46 dBμV

·5 MHz ~ 30 MHz: Quasi-peak 60 dBμV, Average 50 dBμV

Class A Conducted Emission Limits

·150 kHz ~ 500 kHz: Quasi-peak 79 dBμV, Average 66 dBμV

·500 kHz ~ 30 MHz: Quasi-peak 73 dBμV, Average 60 dBμV

Tests must cover all operating modes: no load, 50% load, full load and all functional gears. Multi-interface devices need tests for all interface combinations.

 --Radiated Emission

This test detects electromagnetic waves radiated into the air by operating products, which may interfere with nearby radio receivers.

·Frequency range (per 47 CFR 15.33(b)(1)): Up to 1 GHz for devices with clock frequency below 108 MHz; up to 2 GHz for clock frequency over 108 MHz.

·Test environment: Tests are performed in an anechoic chamber. The product is placed on a rotating turntable, and the antenna scans at different heights with both horizontal and vertical polarization. The maximum radiation value is adopted for judgment, using quasi-peak detection for final verification.

·Limits classification: Test distance is fixed at 3 meters. Class A limits are approximately 10 dB looser than Class B.

Class B Radiated Emission Limits

·30 MHz ~ 88 MHz: 40 dBμV/m

·88 MHz ~ 216 MHz: 43.5 dBμV/m

·216 MHz ~ 960 MHz: 46 dBμV/m

Radiated emission performance is highly affected by wiring layout, shielding design and grounding. Minor changes to PCBA or housing may lead to obvious test result differences.

  3. Class A vs Class B: Key Differences

·Class B: For products used in residential and office environments. Most export consumer electronics including power adapters, lamps, computer peripherals and home appliances belong to Class B with stricter limits.

·Class A: For products used exclusively in industrial and commercial environments. A mandatory warning statement must be printed on labels or manuals: "This is a Class A product. In a domestic environment this product may cause radio interference, in which case the user may be required to take adequate measures."

Classification is determined by the intended usage environment, not the end buyer. Office printers used by commercial companies still belong to Class B.

For FCC SDoC Declaration of Conformity services, please contact Blueasia: 13534225140