RF Emissions & Electromagnetic Compatibility Flashcards
6 cards from real FCC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 RF Emissions & Electromagnetic Compatibility flashcards as text
What distinguishes a Class A digital device from a Class B digital device under FCC Part 15?
Answer: Class A is marketed for use in commercial/industrial environments; Class B is for residential use
FCC Part 15.3 defines Class A devices as those marketed for use in commercial, industrial, or business environments, while Class B devices are marketed for use in a residential environment, requiring more stringent emission limits.
What is the purpose of a 'turntable' in a radiated emissions test setup?
Answer: To rotate the device under test to find the azimuth angle producing maximum emissions
The turntable rotates the EUT (Equipment Under Test) 360 degrees in azimuth so the test engineer can identify the orientation that produces the maximum radiated emission level.
At what frequency does FCC radiated emission testing typically transition from a 3-meter to a 10-meter test distance?
Answer: Above 1 GHz some measurements use 1 m or 3 m per specific rule sections, with 10 m used for certain Part 15 high-power devices
Most Part 15 subpart B devices are tested at 3 meters in a semi-anechoic chamber, but some Part 15 subpart C devices and certain high-power intentional radiators may require 10-meter test distances as specified in the applicable rule sections.
What is the purpose of measuring both horizontal and vertical antenna polarizations during radiated emissions testing?
Answer: Because emissions can be polarized in either orientation and the maximum reading determines compliance
Electromagnetic fields can be polarized horizontally or vertically, so both orientations must be measured and the maximum value of the two is used to determine whether the device meets FCC limits.
What is the 6 dB rule used for in FCC EMC testing?
Answer: Test site validation requires measured site attenuation to be within 4 dB of theoretical values (sometimes referred to as the ±4 dB or 6 dB window)
ANSI C63.4 specifies that a test site is valid if measured normalized site attenuation (NSA) values are within ±4 dB of theoretical free-space NSA, ensuring the site accurately replicates free-space propagation conditions.
Which FCC rule part covers specific absorption rate (SAR) testing for RF exposure from portable devices?
Answer: FCC Part 1 (OET Bulletin 65 / KDB procedures) and Part 2.1093
FCC Part 2.1093 and associated OET Bulletin 65 / KDB guidance establish the SAR limits and testing procedures for evaluating human RF exposure from portable transmitting devices held close to the body.