Calculator Inputs
The page stays in a clean single-column flow, while the input area uses a responsive 3/2/1 grid.
Example Data Table
Sample scenario: 2 W transmitter, 12 dBi gain, 1.5 dB feeder loss, 0.5 dB mismatch loss, 2400 MHz, 8 dBi receive gain, 1 dB receive loss.
| Distance (m) | Peak EIRP (dBm) | Peak E (V/m) | Peak Field (dBµV/m) | Peak Power Density (W/m²) | Estimated Rx Power (dBm) |
|---|---|---|---|---|---|
| 10 | 43.000 | 2.446 | 127.768 | 0.015873 | -10.044 |
| 30 | 43.000 | 0.815 | 118.226 | 0.001764 | -19.586 |
| 100 | 43.000 | 0.245 | 107.768 | 0.000159 | -30.044 |
Formula Used
1) Power Conversion
dBm from watts: P(dBm) = 10 × log10(P(W) × 1000)
Watts from dBm: P(W) = 10(dBm-30)/10
2) Effective Isotropic Radiated Power
Peak EIRP: EIRP(dBm) = Tx Power(dBm) + Tx Gain(dBi) − Tx Loss(dB) − Mismatch Loss(dB)
3) Power Density
Peak power density: S = EIRP(W) / (4πr²)
4) Electric and Magnetic Field
Electric field: E = √(30 × EIRP(W)) / r
Magnetic field: H = E / 377
Field strength in dBµV/m: 20 × log10(E × 1,000,000)
5) Average Values
Average EIRP: Peak EIRP(W) × Duty Cycle Fraction. Average field and density are derived from that reduced power.
6) Free Space Path Loss
FSPL(dB): 32.44 + 20log10(fMHz) + 20log10(dkm)
7) Far-Field Check
Fraunhofer distance: Rff = 2D² / λ, where D is largest antenna dimension and λ is wavelength.
How to Use This Calculator
- Enter the transmitter power and choose its unit.
- Add transmit antenna gain, cable loss, and mismatch loss.
- Enter operating frequency and separation distance.
- Choose the distance unit you prefer for planning.
- Set duty cycle to estimate average exposure values.
- Enter receive gain and loss to estimate receive power.
- Provide the largest antenna dimension for far-field validation.
- Press calculate to view summary metrics, sweep results, graph, and export options.
FAQs
1) What does this RF field strength calculator measure?
It estimates peak and average electric field, magnetic field, power density, EIRP, free space path loss, and approximate receive power from your input scenario.
2) Why is antenna gain included?
Antenna gain concentrates radiated power in a preferred direction. Higher gain raises EIRP and usually increases field strength along the main beam.
3) Why do feeder and mismatch losses matter?
Losses reduce the power that reaches the antenna or aligns with the receiving system. Lower available radiated power means weaker field levels.
4) What does duty cycle change?
Duty cycle affects average power. A transmitter active only part of the time has lower average EIRP, average power density, and average field strength.
5) Is the result valid in the near field?
Not fully. The core equations assume far-field behavior. The Fraunhofer distance check warns when your chosen distance may still be in the near field.
6) Why is receive power only an estimate?
The receive value uses free-space loss. Real deployments may include reflections, fading, diffraction, polarization issues, clutter, and connector imperfections.
7) When should I use dBµV/m instead of V/m?
dBµV/m is useful when comparing field levels across large ranges or matching specifications used in RF testing, coverage work, or EMC-related reporting.
8) Can I export the results?
Yes. After calculation, use the CSV or PDF buttons to export the summary metrics and the distance sweep table for documentation.