RF exposure for amateur stations

Every US amateur station has to meet the FCC's RF exposure limits, whatever its power. A 5 W handheld and a 1,500 W station follow the same rule. What changes is how much work it takes to show you meet it. For most portable and home stations, that's one page of arithmetic and a few habits about where people stand.

Not legal or engineering advice. This page explains the rules and the FCC's published methods in plain terms. The regulations and FCC bulletins linked below are the authority. Independent guide, not affiliated with the FCC or ARRL.

RF exposure v1.0 · written 2026-10-08 · rule text checked on eCFR as of Oct 2026

Calculator: RF exposure check runs the math below in your browser and gives you a summary you can copy for your records.

What the rule says

47 CFR 97.13(c)(1): before transmitting from anywhere people could be exposed above the limits, the licensee must make sure the station complies with §1.1307(b) (and §§2.1091 and 2.1093 where they apply). Amateur stations are pointed to OET Bulletin 65, Supplement B for methods (97.13 on eCFR).
47 CFR 1.1310: the exposure limits themselves, in mW/cm² by frequency (1.1310 on eCFR).
47 CFR 1.1307(b): you either show the station is exempt or do an evaluation. If the FCC asks, you must give it the technical basis for your answer (1.1307 on eCFR).

These rules took effect May 3, 2021. The old power-level exclusions for hams went away, and existing stations had until May 3, 2023 to finish their evaluations (ARRL RF Exposure). If you've never done one, do it now. It's quick.

You don't file anything with the FCC. Keep your numbers so you can produce them on request. Supplement B Appendix B has an optional worksheet and record of compliance, and the calculator's "Copy summary" button gives you a text version.

Two populations, two limits

Who	Limit used	Averaging window	Notes
You, and members of your household who have been told about the exposure and know how to limit it	Controlled (occupational)	6 minutes	97.13(c)(1) lets you use these limits for household members only if they have the right information and training.
Everyone else: neighbors, passers-by, a picnic table full of strangers	Uncontrolled (general population)	30 minutes	About five times stricter on HF.

The uncontrolled limit on HF is 180/f² mW/cm² (f in MHz). On 20 m that's about 0.9 mW/cm². On 6 m and 2 m it's 0.2 mW/cm², the strictest part of the spectrum, because the body absorbs energy best around 30–300 MHz.

Path 1: the exemption check

§1.1307(b)(3)(i)(C) gives a formula. If your time-averaged ERP is at or below the threshold for the distance R (meters) to the nearest person, you're exempt and you're done.

Frequency	Exempt if ERP (W) ≤
0.3–1.34 MHz	1,920 R²
1.34–30 MHz	3,450 R² / f²
30–300 MHz	3.83 R²
300–1,500 MHz	0.0128 R² f
1,500–100,000 MHz	19.2 R²

The HF catch: the exemption only works when R is at least λ/2π. That's about 3.4 m on 20 m, 6.8 m on 40 m and 13 m on 80 m. A park antenna 2 m from the operating table is too close to use the exemption no matter how low the power. Being inside λ/2π doesn't mean you fail. It means you need Path 2.

Path 2: an evaluation

Supplement B accepts tables, formulas, computer modeling or measurement. The simplest is the far-field equation with ground reflection that our calculator uses:

Average power = PEP × duty factor × (time transmitting ÷ averaging window), less any feedline loss.
EIRP = average power × antenna gain (as a ratio, from dBi).
Distance where you meet a limit S: R = √(2.56 × EIRP ÷ (4π × S)). The 2.56 accounts for ground reflection.

Duty factors from Supplement B Table 2: conversational SSB 20% (or 50% with heavy speech processing), conversational CW 40%, FM, RTTY and AFSK 100%. FT8 and other constant-envelope data modes are 100% while transmitting, then you take credit for the receive half of each cycle.

Supplement B's Table 4a gives pre-computed worst-case distances (100% duty). For example, 100 W PEP at 14.35 MHz into a 0 dBi antenna needs 0.7 m controlled and 1.5 m uncontrolled. The table says to multiply by 0.707 for a typical 50% back-and-forth exchange. Our calculator reproduces those numbers.

Far-field formulas get less accurate close to an HF antenna (the reactive near field). There they usually overestimate exposure, which is the safe direction. If a result is close to the line, model the antenna, measure, or add distance.

Worked examples

All use the calculator's defaults: 2.56 ground factor, no feedline loss, half of each averaging window spent transmitting. Distances are from any part of the antenna.

Station	Average power	Uncontrolled distance	Controlled distance	Exemption works from
Park SSB: 100 W PEP, 14.2 MHz, dipole/EFHW 2.15 dBi	10 W	0.61 m (2.0 ft)	0.27 m	3.4 m (λ/2π)
Park FT8: 50 W, 14.074 MHz, 2.15 dBi	25 W	0.96 m (3.1 ft)	0.43 m	3.4 m (λ/2π)
QRP FT8: 10 W, 7.074 MHz, 2.15 dBi	5 W	0.22 m	0.10 m	6.7 m (λ/2π)
Home CW: 100 W, 7.03 MHz, 2.15 dBi	20 W	0.43 m	0.19 m	6.8 m (λ/2π)
2 m FM mobile: 50 W, 146.52 MHz, 3 dBi roof whip	25 W	2.25 m (7.4 ft)	1.01 m	2.8 m

What these show:

HF portable at normal power is easy. Keep the radiating wire, the vertical and its loading coil at least an arm's length from the table and out of the walkway, and the numbers are comfortable. Don't run the hot end of an end-fed half-wave across the picnic table.
VHF FM at 50 W is the one to watch. The 0.2 mW/cm² limit plus a 100% duty mode adds up fast. A roof-mounted whip gets help from the metal roof as a shield for people inside the car, but people standing beside the car are closer than they look. Drop to low power when someone is near the antenna.
Long CQ runs raise your duty factor. A rapid-fire run is closer to 80–90% of the window than 50%. Put realistic minutes into the calculator.

Handhelds

A handheld held near your head falls under the SAR rules for portable devices (§2.1093), not the distance formulas above (2.1093 on eCFR). The calculator doesn't cover that case. Practical habits: use low power when it gets the job done, keep the antenna an inch or more from your face, don't hold the antenna, and use a speaker-mic or a separate antenna for long nets.

Habits / gotchas / checklist

Do the evaluation once for each setup you actually use (home, park kit, mobile) and save it with your station records.
Re-check whenever power, antenna, band, mode or where people can stand changes, like a new amplifier, a beam or a balcony antenna.
Measure from the closest point a person can reach to any part of the antenna, including radials, coils and the feed point of an end-fed wire.
Indoor and attic antennas put the antenna close to people. Run the numbers before the first QSO. See Limited-space antennas.
At a park, people walk past. Assume uncontrolled limits, route wires away from paths, and stop transmitting if someone touches the antenna.
Tune at low power. A tune carrier is 100% duty.

Sources

47 CFR 97.13, 1.1307, 1.1310 on eCFR (checked 2026-10-08).
FCC OET Bulletin 65 (PDF) and Supplement B for amateur stations (PDF). Supplement B predates the 2021 rules, but 97.13(c)(1) still names it as the amateur method. Equipment-level procedures (SAR for portable devices) are in the FCC's Knowledge Database (KDB), which §1.1310 references. Our calculator does not implement KDB device procedures.
ARRL RF Exposure and the ARRL RF Exposure Calculator, a good second check.

Notes & edits

Comments and proposed markdown sit in a queue. Nothing is public until it is reviewed. How this works.