E = √(EIRP · Z₀ / (4π r²)) · ≈ √(30 · EIRP_W) / r · E(dBµV/m) ≈ EIRP(dBm) − 20 log₁₀(r) + 104.77
Power: dBm = 10 log10(P / 1 mW) dBW = dBm − 30 Voltage: dBµV = 20 log10(V / 1 µV) dBmV = dBµV − 60 dBV = dBµV − 120 Current: dBµA = 20 log10(I / 1 µA) Ohm: P = V² / Z = I² · Z = V · I (RMS) 50 Ω offsets (exact 10 log10(50) = 16.9897 dB): dBµV = dBm + 106.99 ≈ dBm + 107 dBµA = dBm + 73.01 ≈ dBm + 73 dBmV = dBm + 46.99 ≈ dBm + 47 0 dBm → 223.6 mV RMS → 4.472 mA RMS General Z: dBµV = dBm + 10 log10(Z) + 90 dBµA = dBm − 10 log10(Z) + 90 Field (free space): E(V/m) = √(30 · EIRP_W) / r(m) S(W/m²) = E² / 377 = EIRP / (4 π r²) H(A/m) = E / 377 AF(dB/m) = E(dBµV/m) − V(dBµV) Ideal AF ≈ 20 log10( 9.73 / (λ √G) ) G linear, λ in m VSWR: Γ = (s−1)/(s+1) RL = −20 log10(|Γ|) mismatch loss = −10 log10(1−|Γ|²)