W5PRO TOOLS / RF EXPOSURE

47 CFR 1.1310 · 1.1307(b) · OET Bulletin 65

RF exposure calculator

Every US amateur station must be evaluated for RF exposure (§97.13(c)). Enter your station and get the minimum distance to keep between the antenna and people, for your household and for everyone else, plus whether you're exempt from a routine evaluation.

Station

Use the highest frequency you'll use on the band. Limits get stricter as frequency rises on HF.
0 is the conservative choice. Feedline loss calculator
Dipole ≈ 2.15 dBi (0 dBd). Use main-lobe gain.
For you and household (controlled limits)
For neighbors and the public (uncontrolled)
Closest point of the antenna to where someone can be.

Read this first

This is the FCC's far-field estimate (OET Bulletin 65, Eq. 3 and 7). It's normally conservative, but it underestimates fields close to small transmitting loops and in the reactive near field of any antenna (closer than about λ/2π). If people can get that close, measure or model instead.

Your evaluation is your responsibility as the licensee, and you should keep a record of it. This tool helps you do the math; it isn't a substitute for the rules.

How it works

Average power. PEP × feedline loss × mode duty factor × the share of the averaging window you transmit: 6 minutes for controlled limits, 30 for uncontrolled (§1.1310(b)–(c); OET 65 Supplement B p.13). Duty factors are from Supplement B Table 2. Modern digital modes (FT8, PSK31) aren't in that 1997 table, so they're treated like AFSK at 100%.

Power density. S = k · EIRP / (4πR²), where EIRP is the average power times numeric antenna gain and k is the ground-reflection factor: 2.56 in the FCC/EPA model (OET 65 Eq. 7). The minimum distance is where S equals the limit. dBd is converted with +2.15 dB; ERP = EIRP / 1.64.

Who gets which limit. §97.13(c)(1) lets you evaluate yourself and your household against the controlled limits, as long as they have the appropriate training and information. Everyone else (neighbors, passers-by, guests) is evaluated against the uncontrolled (general population) limits.

Exemption. §1.1307(b)(3)(i)(C) exempts a source from routine evaluation if its time-averaged ERP is below the table threshold at the separation distance, and only where that distance is at least λ/2π. The 30-minute average ERP is used here.