RF Exposure Calculator
Magnetic Loop RF Exposure Calculator
FCC Approved Methods for Station Evaluation
Source: FCC, OET Bulletin 65 Sup B (1997) p 15
Commission's limits on human exposure to radiofrequency (RF) electromagnetic fields. Amateurs can select from a number of technically valid methods that can be useful in performing the required station evaluations. In general, it will be appropriate to use one of the following methods:
Estimated compliance distances using tables developed from field-strength equations
Estimated compliance distances using tables derived from antenna modeling
Estimated compliance distances using antenna modeling (NEC, MININEC, etc.)
Estimated compliance distances using field-strength equations
Estimated compliance distances using software developed from field-strength equations
Estimated compliance distances using calibrated field-strength measurements
FCC Limits for maximum Permissible Exposure (MPE) Source: FCC, OET Bulletin 65 (1997) p 67
Assumptions and mathematical determination
The process for estimating compliance distances using field-strength equations to find the minimum safe distance is a twenty plus step process as loop current must be determined to estimated field strength;
Determine loop current from User inputs, used for H Field determination
Determine EIRP from User inputs, used for E Field determination
Determine MPE from Table 1 Limits for Maximum Permissible Exposure, FCC, OET Bulletin 65 (1997) p 67, calculated from the frequency input
Solve distance (R) using Biot-Savart Law, magnetic field of solenoids to determine H Field Strength
Magnetic field = µo I R^2 / [ 2 (Distance^2 + R^2)^3/2
Solve for E Field Strength at distance (R) using the power density and field strength equations, from FCC, OET Bulletin 65 (1997) pp 9, 19-21
S = EIRP / 4∏R^2 = E2 / 3770 = 37.7 H^2.
Utilizing the repetition of a sequence of operations calculate H and E Fields at 1 cm intervals moving outward from the antenna until both fields are less than their respective MPE.
Repeated for controlled and uncontrolled.