Test Distance Conversion (Limit 3 m ↔ 10 m)
Convert limits or readings between test distances. 10 m → 3 m is about +10.46 dB.
Worked example
Input: Limit / level at original distance 40 dBµV/m, Original distance 10 m, Target distance 3 m, Distance exponent 20 dB/decade
Result: Converted level 50.4576 dBµV/m, Correction 10.4576 dB
Result: Converted level 50.4576 dBµV/m, Correction 10.4576 dB
Formula
L₂ = L₁ + n·log₁₀(d₁ / d₂)
Default n = 20 (field strength inversely proportional to distance)
How it works
If the radiated field falls off inversely with distance, converting from d₁ to d₂ is 20·log₁₀(d₁/d₂) dB. Use it when measuring at 3 m against a 10 m limit, or when comparing results taken at different distances.
Practical tipStandards often tabulate the 3 m limit as a rounded value (for example +10 dB) rather than the computed +10.46 dB. Always use the limit printed in the standard for compliance decisions, and use this calculator for estimates and cross-checks.
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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