Choosing a Shielded Door: Strengthen the Room's Weakest Link
The door is the most common cause of lost performance in shielded rooms. We cover door types and why maintenance matters.
3 min readAugust 26, 2026
The Logic of the Measurement
A transmitting antenna is placed outside the room and a receiving antenna inside. A reference measurement is first taken without the room, then the same measurement is repeated with the room wall in between.
The difference between the two measurements shows by how many dB the room attenuates the signal at that frequency.
Which Points Are Measured?
Measurements are taken not only in the middle of walls but at weak points such as door edges, ventilation filters, cable penetrations and panel joints.
Frequencies are usually chosen from different bands, from low magnetic fields up to GHz.
Which Standard?
EN 50147-1 is widely used in Europe and IEEE 299 in the US. Military projects may still require MIL-STD-285.
The standard to be applied and the acceptance limits should be stated clearly in the contract.
How to Read the Results
The test report shows the attenuation at each frequency and measurement point. The most important value isn't the average but the lowest, because a room is only as good as its weakest point.
When comparing report values, watch the frequency range and method. Our articles on reading dB values and writing the specification are a guide. For our measurement service, see the shielding testing page.
Frequently Asked Questions
Must the room be vacated for measurement?
Yes, no work should be done in the room during measurement and it should be in its final operating state.
Is calibration of the measuring equipment needed?
Yes. For the report values to be reliable, equipment calibration must be valid.
How often should measurement be done?
Most organizations measure once a year; more frequent measurement is recommended for heavily used rooms.
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