The direct answer
Radiated emission testing measures how much electromagnetic noise your product broadcasts into the air, and EN IEC 55014-1 caps it at 40 dBµV/m from 30-230 MHz and 47 dBµV/m from 230 MHz-1 GHz, measured at 3 meters. In our Model 1338 report, the charging case passed this test with margin - the emissions from its charging circuit stayed below the limit across the whole band. A product that fails this test is not just non-compliant; it is a small radio polluter that can degrade other electronics nearby.
Why a charging circuit can act like a transmitter
Every switching regulator produces noise as it chops power. That noise travels along the PCB traces and cables, and cables act like antennas - which is exactly why a USB charging case can radiate. The usual suspects:
- Switching regulators and their layout.
- USB ports and cables acting as radiating elements.
- Poor grounding and shield terminations.
- Long internal wiring routed near the shell edge.
None of this means the product is broken; it means the electronics need to be designed for silence, not just for function.
The limits, in plain language
|
Frequency band |
Limit at 3 m |
Detector |
|
30 MHz - 230 MHz |
40 dBµV/m |
Quasi-peak |
|
230 MHz - 1 GHz |
47 dBµV/m |
Quasi-peak |
dBµV/m is a logarithmic measure of field strength; the numbers sound small, but each 20 dB is a factor of ten in power. Quasi-peak is a detector that weights repetitive noise the way a real radio receiver perceives it - which is why the test method matters as much as the limit.
How the test actually runs
- The product operates in its normal mode - for the 1338, charging function active, supplied by its power bank.
- The product sits on a turntable in a 3-meter semi-anechoic chamber, the room that kills reflections so measurements are honest.
- A receiving antenna measures the emissions, first horizontally, then vertically - because the product radiates differently in each polarization.
- The product rotates and the antenna height scans to catch the worst-case direction.
- The measured level is corrected for antenna factor, cable loss and pre-amplifier gain to get the final level, which is compared to the limit.
Our report shows the horizontal and vertical measurement data, with the final level calculated the same way on both pages - reading level plus antenna factor plus cable loss minus pre-amplifier gain.
Factory data: When we sent the 1338 for testing, we asked the lab to run it in the real charging mode with the actual power bank - not a lab substitute. Emissions depend on the current the circuit draws, so a test with a dummy load would have told us nothing about the product we actually ship.
What "Pass" means
Pass means the measured emissions stayed below the limit across the whole 30 MHz-1 GHz range, in both polarizations, in the worst-case orientation. It does not mean zero emission - nothing electronic is silent - it means the noise is low enough that it will not cause problems for other equipment and meets the legal limit.
Industry need: why buyers should ask for this page
The radiated emission page is the one most buyers never open, and it is the one that protects the environment the product will live in - the cabin, the office, the hotel room. For EU market access it is a CE requirement under the EMC Directive; for US programs, the equivalent scope is FCC Part 15, which needs its own assessment. Asking to see the emission pages and their margins tells you whether the factory tested a real configuration or a convenient one.
FAQ
What frequency range does radiated emission cover?
For EN IEC 55014-1 with a product clock below 108 MHz, the range is 30 MHz to 1 GHz, which is what our report covers. Products with higher clock frequencies extend to 2, 5 or 6 GHz.
What does 40 dBµV/m mean?
It is the field strength limit measured at 3 meters, expressed in decibels relative to one microvolt per meter. Lower is quieter; staying below the line is the pass condition.
Which part of a suitcase radiates?
The electronics - switching regulators, charging circuits, USB ports and the cables connected to them. The shell is not the emitter; the circuit board and wiring are.
Can a product pass emissions but fail immunity?
Yes - the two are independent tests with independent fixes. A quiet product can still be easily disturbed, and a robust product can still be noisy. That is why both halves of EMC are tested.
Does a battery-powered product need radiated emission testing?
Yes - battery power removes the mains tests, but radiated emission applies to any electronic product regardless of power source. The noise leaves through the air, not only through the power cord.
What margin should a good report show?
Comfortable margin is better than a squeaked pass. Our 1338 passed with margin across the band; if a report shows results hugging the limit line, ask the factory what margin they expect on production units.
About this report
The radiated emission data in this article comes from report No. GTS2025080251E01 for our Model 1338 - measured at 3 m in a semi-anechoic chamber, horizontal and vertical polarization, 30 MHz-1 GHz, pass. We share the emission pages with buyers and, when needed, run the same discipline for FCC Part 15 programs through accredited labs. Ask for the pages at clkbusiness@clkluggage.com or WhatsApp +86-18879628221.