Radio Frequency Exposure

As of May 2021, the FCC has required that all new amateur radio stations calculate their radio systems’ radio frequency (RF) exposure. As of May 2023, the FCC has required all stations to have calculated their RF exposure. The purpose of these calculations is to document what the minimum safe approach distances are for each antenna/band you operate. First, don’t worry or panic. A typical 100-watt twenty-meter radio with 3 dB of coax loss intermittently operating SSB produces a minimum approach distance of about 9 inches. This regulation aims to know what your system produces and be aware of the potential issues. Calculate your conditions and either print them out or create a PDF that you can keep with your station logs.

The easy way to quantify the RF Exposure of your station’s antenna farm is to use the ARRL’s RF exposure calculator at https://www.arrl.org/rf-exposure-calculator. The calculator will give you the power density factor and the minimum approach distance in two cases: the controlled situation (antenna at the top of a tower or in a caged area) and the uncontrolled situation (antenna in a backyard).

When you use this calculator, you will need to know the following information:

• Power at Antenna: (watts) – Most of us operate radios in the 100-watt range. You will also need to know how much coax loss you have. For example, if you have 3 dB of coax loss, you will have 50 watts of power at your antenna.
• Mode duty cycle – This would be the type of emissions you typically use. Ie. SSB, CW, FM, AM, RTTY, etc. There is a drop-down box that contains the options available.
• Transmit duty cycle – How much time you spend transmitting. For example, do you typically transmit for 5 minutes and then receive for 10 minutes?
• Antenna Gain (dBi): This should be the gain for the antenna you are testing in dBi. If you are unsure, the RSBG has provided a typical gain chart for various antennas, shown below.
• Operating Frequency (MHz) – This is the frequency you test for. You will need to test each of the bands you typically use.

Antenna Gain Chart

Antenna Type	Approx. Gain (dBi) *
Half wave dipole	2.15 dBi
10 element Yagi	15.1 dBi
2 element Yagi	5.9 dBi
3 element Yagi	8.1 dBi
4 element Yagi	9.1 dBi
5 element Yagi	10.1 dBi
6 element Yagi	11.1 dBi
8 element Yagi	13.1 dBi
Delta Loop	5.2 dBi
Four Square	5.2 dBi
G5RV	1.0 dBi
Hex Beam	5.0 dBi
Moxon	6.0 dBi
Quarter Wave Vertical	1.5 dBi
Windom (OCD)	2.0 dBi

More information is available on the ARRL’s RF Exposure web page at https://www.arrl.org/fcc-rf-exposure-regulations-the-station-evaluation.