# Monopole & Dipole RF Exposure Calculator

This JavaScript RF Hazard Calculator is a practical web-based application proving the user with estimated distances that are credible using FCC safety compliant methods. The calculator estimates field strengths using FCC equations from FCC, OET Bulletin 65. Each case assumes maximum or peak conditions as a simplified static case. JavaScript programming language was selected as the best way to deliver a client-side interactive web page and is simply the best way to get an online calculator built. JavaScript is similar to a spreadsheet for math capability. It is not a good language to solve differential equations or a complex numerical problem. In this case the JavaScript application meets the need. When an algorithm was too complex it was simplified and these equations were replaced with brute force loops that run until a solution is within a range specified. All cases requiring a constant were given a worst-case boundary or split into multiple single worst cases that each determined the maximum distance required for safety and reports the maximum result. This simplification process is commonly used in engineering to quickly identify issues and is one of the FCC compliant method to determine human exposure to radiofrequency (RF) electromagnetic fields. It is not used to determined how well an antenna will work like the EZNEC or 4NEC2 finite element method programs.

# 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

# Source: FCC, OET Bulletin 65 (1997) p 67 # The process for estimating compliance distances using field-strength equations to find the minimum safe distance is a simple two-step process;

1. Determine MPE from Table 1 Limits for Maximum Permissible Exposure, FCC, OET Bulletin 65 (1997) p 67, calculated from the frequency input by the user.

2. Rearrange the power density equation, S = EIRP / 4∏R^2 from FCC, OET Bulletin 65 (1997) p 19 to solve for distance (R) at a specific MPE.

3. Repeated for controlled and uncontrolled. Assumptions:

• Always include 4.1 dB (2.56) for ground reflection factor based on FCC, OET Bulletin 65 (1997) pp 20-21 and let the user increase losses should they desire a free space solution.

• Duty Cycle is a direct percentage of power.

• Minimum power of 5 W limit was subjective.

• Maximum power of 1500 W limit is the highest allowed by FCC Part 97.

• Minimum frequency of 1 MHz limit was subjective.

• Maximum frequency of 100 GHz limit is the highest listed in the FCC MPE table.

• Antenna Gain of +/- 20 dB was subjective.

• Tuner and cable losses of 0 to -10 dB was subjective.