Blog - RF Exposure Rule Compliance

Update on Aug 2, 2021: the September issue of QST has a free article about Understanding the Changes to the FCC RF Exposure Rules.

The FCC has announced that rule changes detailed in a lengthy 2019 Report and Order governing RF exposure standards go into effect on May 3, 2021. The new rules do not change existing RF exposure (RFE) limits but do require that stations in all services, including amateur radio, be evaluated against existing limits, unless they are exempted. For stations already in place, that evaluation must be completed by May 3, 2023. For more information see: www.arrl.org/news/updated-radio-frequency-exposure-rules-become-effective-on-may-3

We have two ways to comply with the rules. One method involves taking measurements with the appropriate instruments. Another method is a predictive model with calculations based on antenna theory and documented properties of the transmitters and antennas at your station.

Below are some of the RF exposure calculations I created for the antennas at my station using a calculator that is available on-line. See below the table for links to sources of the information and the calculator that I used.

I also found a spreadsheet from Ham Radio School, adapted and updated it to create this spreadsheet that seems to be easier to produce calculations.

I used the most conservative estimates possible. For example, I assumed a 100 percent duty cycle on FM and entered the maximum power rating for each band from the tech specs for my radios. I chose not to calculate power losses from feedline. You might want to use a feedline power loss calculator to estimate a more accurate power level at your feed point.
Please let me know if you see any mistakes.

I used the Calculator at: hintlink.com/power_density.htm



Antenna and CalculationBand StartBand End
Comet CX-33370cm Band Gain per Comet
Average Power at the Antenna 35 watts 35 watts
Antenna Gain in dBi 9 dBi 9 dBi
Distance to the Area of Interest in Feet 48 feet  48 feet 
Distance to the Area of Interest in Meters 14.6304 metres 14.6304 metres
Frequency of Operation 420 MHz450 MHz
Are Ground Reflections Calculated? Yes  Yes 
Estimated RF Power Density 0.0265 mW/cm2 0.0265 mW/cm2
Controlled MPE 1.405 mW/cm2 1.505 mW/cm2
Controlled Distance to Compliance From Centre of Antenna Feet 6.6489 feet 6.4251 feet
Controlled Distance to Compliance From Centre of Antenna Meters 2.0266 metres 1.9584 metres
Uncontrolled MPE 0.285 mW/cm2 0.305 mW/cm2
Uncontrolled Distance to Compliance From Centre of Antenna Feet 14.8055 feet 14.3052 feet
Uncontrolled Distance to Compliance From Centre of Antenna Meters 4.5127 metres 4.3602 metres
Does the Area of Interest Appear to be in Compliance? yes yes
Comet CX-333 1.25 M Band Gain per Comet
Average Power at the Antenna 70 watts 70 watts
Antenna Gain in dBi 7.8 dBi 7.8 dBi
Distance to the Area of Interest in Feet 48 feet  48 feet 
Distance to the Area of Interest in Meters 14.6304 metres 14.6304 metres
Frequency of Operation 222 MHz225 MHz
Are Ground Reflections Calculated? Yes  Yes 
Estimated RF Power Density 0.0402 mW/cm2 0.0402 mW/cm2
Controlled MPE 1.005 mW/cm2 1.005 mW/cm2
Controlled Distance to Compliance From Centre of Antenna Feet 9.6672 feet 9.6672 feet
Controlled Distance to Compliance From Centre of Antenna Meters 2.9466 metres 2.9466 metres
Uncontrolled MPE 0.205 mW/cm2 0.205 mW/cm2
Uncontrolled Distance to Compliance From Centre of Antenna Feet 21.5547 feet 21.5547 feet
Uncontrolled Distance to Compliance From Centre of Antenna Meters 6.5699 metres 6.5699 metres
Does the Area of Interest Appear to be in Compliance? yes yes
Comet CX-333 base mounted at 48' height 2 M Band Gain per Comet
Average Power at the Antenna 50 watts 50 watts
Antenna Gain in dBi 7.8 dBi 7.8 dBi
Distance to the Area of Interest in Feet 48 feet  48 feet 
Distance to the Area of Interest in Meters 14.6304 metres 14.6304 metres
Frequency of Operation 144 MHz 148 MHz
Are Ground Reflections Calculated? Yes  Yes 
Estimated RF Power Density 0.0287 mW/cm2 0.0287 mW/cm2
Controlled MPE 1.005 mW/cm2 1.005 mW/cm2
Controlled Distance to Compliance From Centre of Antenna Feet 8.178 feet 8.178 feet
Controlled Distance to Compliance From Centre of Antenna Meters 2.4927 metres 2.4927 metres
Uncontrolled MPE 0.205 mW/cm2 0.205 mW/cm2
Uncontrolled Distance to Compliance From Centre of Antenna Feet 18.2248 feet 18.2248 feet
Uncontrolled Distance to Compliance From Centre of Antenna Meters 5.5549 metres 5.5549 metres
Does the Area of Interest Appear to be in Compliance? yes yes
Radiowavz DX80PL OCF Dipole 10 M Band Gain estimates
Average Power at the Antenna 100 watts 100 watts
Antenna Gain in dBi 10.77 dBi 10.77 dBi
Distance to the Area of Interest in Feet 36 feet  36 feet 
Distance to the Area of Interest in Meters 10.9728 metres 10.9728 metres
Frequency of Operation 28 MHz29.7 MHz
Are Ground Reflections Calculated? Yes  Yes 
Estimated RF Power Density 0.2021 mW/cm2 0.2021 mW/cm2
Controlled MPE 1.153 mW/cm2 1.0253 mW/cm2
Controlled Distance to Compliance From Centre of Antenna Feet 15.1521 feet 16.069 feet
Controlled Distance to Compliance From Centre of Antenna Meters 4.6184 metres 4.8978 metres
Uncontrolled MPE 0.2346 mW/cm2 0.2091 mW/cm2
Uncontrolled Distance to Compliance From Centre of Antenna Feet 33.8193 feet 35.8696 feet
Uncontrolled Distance to Compliance From Centre of Antenna Meters 10.3081 metres 10.933 metres
Does the Area of Interest Appear to be in Compliance? yes yes
Radiowavz DX80PL OCF Dipole 15 M Band Gain estimates
Average Power at the Antenna 100 watts 100 watts
Antenna Gain in dBi 9.58 dBi 9.58 dBi
Distance to the Area of Interest in Feet 36 feet  36 feet 
Distance to the Area of Interest in Meters 10.9728 metres 10.9728 metres
Frequency of Operation 24.89 MHz24.99 MHz
Are Ground Reflections Calculated? Yes  Yes 
Estimated RF Power Density 0.1537 mW/cm2 0.1537 mW/cm2
Controlled MPE 1.4578 mW/cm2 1.4462 mW/cm2
Controlled Distance to Compliance From Centre of Antenna Feet 11.7559 feet 11.8029 feet
Controlled Distance to Compliance From Centre of Antenna Meters 3.5832 metres 3.5975 metres
Uncontrolled MPE 0.2956 mW/cm2 0.2932 mW/cm2
Uncontrolled Distance to Compliance From Centre of Antenna Feet 26.2251 feet 26.3303 feet
Uncontrolled Distance to Compliance From Centre of Antenna Meters 7.9934 metres 8.0255 metres
Does the Area of Interest Appear to be in Compliance? yes yes
Radiowavz DX80PL OCF Dipole 20 M Band Gain estimates
Average Power at the Antenna 100 watts 100 watts
Antenna Gain in dBi 10.67 dBi 10.67 dBi
Distance to the Area of Interest in Feet 36 feet  36 feet 
Distance to the Area of Interest in Meters 10.9728 metres 10.9728 metres
Frequency of Operation 14.0 MHz 14.350 MHz
Are Ground Reflections Calculated? Yes  Yes 
Estimated RF Power Density 0.1975 mW/cm2 0.1975 mW/cm2
Controlled MPE 4.5968 mW/cm2 4.3756 mW/cm2
Controlled Distance to Compliance From Centre of Antenna Feet 7.5146 feet 7.7012 feet
Controlled Distance to Compliance From Centre of Antenna Meters 2.2905 metres 2.3473 metres
Uncontrolled MPE 0.9234 mW/cm2 0.8791 mW/cm2
Uncontrolled Distance to Compliance From Centre of Antenna Feet 16.7414 feet 17.1587 feet
Uncontrolled Distance to Compliance From Centre of Antenna Meters 5.1028 metres 5.23 metres
Does the Area of Interest Appear to be in Compliance? yes yes
Radiowavz DX80PL OCF Dipole 30 M Band Gain estimates
Average Power at the Antenna 100 watts 100 watts
Antenna Gain in dBi 7.34 dBi 7.34 dBi
Distance to the Area of Interest in Feet 36 feet  36 feet 
Distance to the Area of Interest in Meters 10.9728 metres 10.9728 metres
Frequency of Operation 10.1 MHz 10.150 MHz
Are Ground Reflections Calculated? Yes  Yes 
Estimated RF Power Density 0.0918 mW/cm2 0.0918 mW/cm2
Controlled MPE 8.8277 mW/cm2 8.741 mW/cm2
Controlled Distance to Compliance From Centre of Antenna Feet 3.7203 feet 3.7385 feet
Controlled Distance to Compliance From Centre of Antenna Meters 1.1339 metres 1.1395 metres
Uncontrolled MPE 1.7695 mW/cm2 1.7522 mW/cm2
Uncontrolled Distance to Compliance From Centre of Antenna Feet 8.257 feet 8.2976 feet
Uncontrolled Distance to Compliance From Centre of Antenna Meters 2.5167 metres 2.5291 metres
Does the Area of Interest Appear to be in Compliance? yes yes
Radiowavz DX80PL OCF Dipole 40 M Band Gain estimates
Average Power at the Antenna 100 watts 100 watts
Antenna Gain in dBi 6.11 dBi 6.11 dBi
Distance to the Area of Interest in Feet 36 feet  36 feet 
Distance to the Area of Interest in Meters 10.9728 metres 10.9728 metres
Frequency of Operation 7 MHz7.3 MHz
Are Ground Reflections Calculated? Yes  Yes 
Estimated RF Power Density 0.0691 mW/cm2 0.0691 mW/cm2
Controlled MPE 18.3723 mW/cm2 16.8937 mW/cm2
Controlled Distance to Compliance From Centre of Antenna Feet 2.2579 feet 2.3525 feet
Controlled Distance to Compliance From Centre of Antenna Meters 0.6882 metres 0.717 metres
Uncontrolled MPE 3.6785 mW/cm2 3.3827 mW/cm2
Uncontrolled Distance to Compliance From Centre of Antenna Feet 4.987 feet 5.1986 feet
Uncontrolled Distance to Compliance From Centre of Antenna Meters 1.52 metres 1.5845 metres
Does the Area of Interest Appear to be in Compliance? yes yes
Radiowavz DX80PL OCF Dipole 80 M Band Gain estimates
Average Power at the Antenna 100 watts 100 watts
Antenna Gain in dBi 4.94 dBi 4.94 dBi
Distance to the Area of Interest in Feet 36 feet  36 feet 
Distance to the Area of Interest in Meters 10.9728 metres 10.9728 metres
Frequency of Operation 3.5 MHz4.0 MHz
Are Ground Reflections Calculated? Yes  Yes 
Estimated RF Power Density 0.0528 mW/cm2 0.0528 mW/cm2
Controlled MPE 73.4744 mW/cm2 56.255 mW/cm2
Controlled Distance to Compliance From Centre of Antenna Feet 1.0148 feet 1.1527 feet
Controlled Distance to Compliance From Centre of Antenna Meters 0.3093 metres 0.3513 metres
Uncontrolled MPE 14.6989 mW/cm2 11.255 mW/cm2
Uncontrolled Distance to Compliance From Centre of Antenna Feet 2.2074 feet 2.5156 feet
Uncontrolled Distance to Compliance From Centre of Antenna Meters 0.6728 metres 0.7668 metres
Does the Area of Interest Appear to be in Compliance? yes yes