RF Exposure Calculator

v2.2 (2021-05-07) by Paul Evans, VP9KF , Hintlink Technology.
Help page.<-- to see CHANGES, go here
Calculate Radio Frequency Exposure
The average power at the antenna:
In watts
The antenna gain in dBi:
Enter 2.2 for dipoles; add 2.2 for antennas rated in dBd
The distance to the area of interest:
From the centre of the antenna, in metres
The frequency of operation:
In MHz

Ground Reflection Effects
In most cases, the ground reflection factor is needed to provide a truly worst-case estimate of the compliance distance in the main beam of the antenna. Including the ground reflection effects may yield more accurate results especially with very low antennas, non-directional antennas, and calculations below the main lobe of directional antennas.

Do you wish to include effects of ground reflections? Yes No

This is a main beam power density estimation program intended for use as part of a evaluation of RF safety compliance with FCC regulations. Amateur Radio operators licensed by the Federal Communications Commission of the United States of America are required to do an evaluation of the strength of the RF fields around their stations, with the only exemption being ERP of less than or equal to 0 dBm (1mW). These rules can be found in the FCC's ET Docket No. 19-126A1. More information can be found at the ARRL Website RF Exposure page.

This program uses the formulae given in FCC OET Bulletin No. 65 to estimate power density in the main lobe of an antenna, with use of the EPA-recommended ground reflection factor as an option. This program is intended for approximate far-field calculations. It may overestimate the actual field strength of high-gain antennas in the near field (within several wavelengths of the antenna). However, it may also underestimate the strength of fields that may be encountered in hot spots in the near field. No computer program can accurately predict where wiring or reflective objects may create hot spots in your particular installation.

This is a World Wide Web front end for a public domain program written by W4/VP9KF using PHP.

Terms: GNU Licence.

No Warranties: This information is provided "as is" without any warranty, condition or representation of any kind, either express or implied, including but not limited to, any warranty respecting non-infringement, and the implied warranties of conditions of merchantability and fitness for a particular purpose. In no event shall we be liable for any direct, indirect, special, incidental, consequential or other damages howsoever caused whether arising in contract, tort, or otherwise, arising out of or in connection with the use or performance of the information contained on this web site.

Exemptions
to Routine RF Exposure Evaluations

On 2019-11-27, in a  Report and Order of 159 pages, the FCC adopted no categorical exemption to routine RF exposure compliance testing at all Amateur Radio operating frequencies. Moreover, all stations, regardless of power level (except 0 dBm and less), must comply with the RF exposure limits.

Average Power Estimate

When amateurs are required to perform a routine evaluation of the RF exposure around their stations, the FCC regulations on permissible RF exposure are not based on peak envelope power (PEP), but on average power over a 30 minute time period for uncontrolled environments or a 6 minute time period for controlled environments.

Operating Mode Duty Factor
Conversational SSB, no processing
20%
Conversational SSB, with processing
40%
[Voice] FM
100%
FSK or RTTY
100%
AFSK [SSB]
100%
FT4/FT8
50%
Conversational CW
40%
Carrier
100%

To estimate your average power, first start with your Peak Envelope Power (PEP). Multiply that by the duty factor for the mode you are using, then by the maximum percentage of time you expect to operate within the averaging period.

For example, if you operate a 1500 watt PEP SSB (phone) station that is on for 10 minutes, off for 10 minutes and on again for 10 minutes, you are operating with 200 watts average power (1500 watts PEP * 20% * 67% = 200 watts average power) over a 30 minute period. If you operate a 1500 watt Morse Code (CW) station over the same time period, you have 1500 watts * 40% * 67% or 400 watts average power.

In most cases for the 6 minute controlled environment exposure estimate, you should probably assume that it is possible to operate over the entire 6 minute period, so the 1500 watt PEP SSB phone station would be 300 watts average power for controlled-exposure calculations. An RTTY, digital station, beacon station or FM repeater transmitter could possibly be on for the full 30 minute time period. The RTTY station or FM repeater would have 1500 watts average power. If it operated 10 minutes on, 10 minutes off and 10 minutes on, it would have 1000 watts average power over 30 minutes.