Shielding Effectiveness / Insertion Loss from Readings

Shielding effectiveness or filter insertion loss from before/after readings, with attenuation ratio and transmitted-power percentage.

Worked example

Input: Reference reading (without shield) 60 dBµV, Reading with shield 25 dBµV
Result: Shielding effectiveness / insertion loss 35 dB, Voltage (field) attenuation 56.2341 ×, Transmitted power 0.0316228 %

Formula

SE = V_ref − V_shielded (dB)

Transmitted power = 10^(−SE/10) × 100 %

How it works

Shielding effectiveness and insertion loss are defined the same way: the reading without the shield (or filter) minus the reading with it. 35 dB means the voltage (field) drops by about 56× and only about 0.03 % of the power gets through.

Practical tipKeep antenna positions, cable routing and source level identical between the two measurements. SE depends strongly on near vs. far field and on electric vs. magnetic field, so record the conditions along with the result.

Related calculators

Related guides

Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data. Last updated: 2026-10-10