James Yates

EMC — Tool

Field strength calculator

Convert field-strength units or calculate the relationship between transmitter power, antenna gain, distance and field strength. See standards placement checks for antenna geometry.

1 — Convert a field value

Enter a value and select its unit to update all equivalents. Calculations assume plane-wave far-field conditions: H = E / 377 Ω.

Input

Magnetic and power-density figures assume the plane-wave relationship, valid in the far field.

Equivalents

2 — Field ↔ power at a distance

Calculate field strength, transmitter power or distance under far-field conditions.

E  =  √30 · P · Gd

Inputs

Typical horn 8–15 dBi; log-periodic 6–7 dBi; biconical ≈ 2 dBi mid-band.

Results

Calculations assume far-field, free-space conditions and exclude chamber reflections, near-field gain reduction and cable loss. Allow amplifier headroom for modulation and check antenna performance at the test distance. For 1 kHz, 80% AM, the amplifier must support the modulation peak. Refer to the standards placement page for placement and spacing checks.