Note
Hazardous RF radiation limits and recommended distances may vary by
country. Observe all applicable state and federal regulations when using this
transmitter.
To perform calculations to understand the safe exposure margin (MPE), use the following
formula suggested by OET 65. The calculations provided are for common antennas often
utilized in the ENG environment.
Calculating MPE
EIRP = P * (10 ^ (G / 10)) = (antilog of G/10) * P
P = RF power delivered to the antenna in mW
G = Power gain of the antenna in the direction of interest relative to an isotropic radiator
R = distance to the center of radiation of the antenna in centimeters
S = MPE in mW/cm² (milliwatts per square centimeters)
Conversions
dBi to numeric gain = Antilog (dBi/10)
Feet to centimeters = Feet * 30.48
Centimeters to Feet = cm * .0328
4
π = 12.57
User Input
RF power delivered to the antenna = Watts
Antenna gain (referenced to isotropic antenna) = dBi
Distance from the center of radiation = Feet
Calculation steps:
1. [P] RF power input. Watts to milliwatts = Watts * 1000
2. [G] Antenna gain dBi. Numeric gain = Antilog (dBi/10)
3. [EIRP] Multiply P * G
4. [R] Centimeters to feet = Centimeters * .0328
5. Square R
6. Multiply R² * 4
π
7. [S] Divide (R² * 4
π) into EIRP
S = Power Density in milliwatts per square centimeters.
Note
At frequencies above 1500 MHz, S must not be greater than 1.
Reference
FCC OET Bulletin 65, August 1997 - Evaluating Compliance with FCC Guidelines for Human
Exposure to Radio Frequency Electromagnetic Fields
2
HDX-1100 User and Technical Manual
