Shielding verification

Goal

Quantify the actual installed attenuation of a shielding measure, rather than relying on the datasheet figure.

Equipment

• Broadband RF power-density meter
• RF spectrum analyser
• Directional antenna (log-periodic or horn)

Procedure

1. Before installation, record fixed-position readings in both peak and average mode, with the dominant source direction noted.
2. Where possible use a stable reference source rather than ambient network traffic, whose level changes minute to minute.
3. Install the measure, then repeat the readings at the identical positions with identical meter settings.
4. Express the result as a ratio and in dB: 10 · log₁₀(S_before / S_after).
5. Check the perimeter, seams, window reveals and any penetration for leakage, which usually dominates the result.
6. Confirm no new problem was created: re-measure the AC electric field if a conductive surface was installed.

Pitfalls

• Using ambient cellular traffic as the reference, so the before/after difference is mostly network load variation
• Expecting the datasheet dB figure; installed performance is routinely 10–20 dB worse
• Ignoring reflection: enclosing a transmitter can raise levels inside the enclosure
• Leaving a conductive surface ungrounded and increasing the low-frequency electric field

Interpret results against

• Shielding attenuation

Related records

• Carbon or nickel shielding paint

  A conductive coating applied to walls and ceilings, quoted at 30–40 dB in the cellular bands; it must be bonded to a grounded conductive strip to also control low-frequency electric fields.

  Shielding & remediation

• RF-attenuating window film

  A metallised film bonded to glazing, typically quoted at 20–35 dB, and usually the highest-value single intervention because glass is the dominant entry path for outdoor RF.

  Shielding & remediation

Sources

1. sbm-2024 Building Biology Evaluation Guidelines for Sleeping Areas (SBM-2024) — Institut für Baubiologie + Nachhaltigkeit (IBN), 2024. ngo, link checked 2026-08-12.