RF Exposure Calculator

FCC MPE limits are based on time-averaged exposure, not peak transmitter power, so the calculator scales your effective radiated power by a duty cycle factor — roughly 40% for SSB voice since you're only transmitting while talking, close to 100% for FM/digital, and about 50% for CW. The same 100W SSB rig produces meaningfully less average exposure than a 100W FM repeater running continuously.

The calculator implements the FCC's frequency-dependent MPE curve published in OET Bulletin 65 (implementing 47 CFR § 1.1310): a flat 100 mW/cm² below 1.34 MHz, a 900/f² (controlled) and 180/f² (uncontrolled) curve through HF, flat 1.0/0.2 mW/cm² limits from 30-300 MHz (covering the popular 2m and 70cm ham bands), and a rising limit above 300 MHz. This reflects how the body absorbs RF energy differently across the spectrum, with VHF/UHF generally being where whole-body absorption is most efficient, hence the stricter flat limits there.

The controlled limit applies to the operator and people who understand and can control their RF exposure, like family members in the shack who know to keep their distance. The uncontrolled limit is stricter and applies to the general public — neighbors or passersby who haven't been informed about the exposure and can't be expected to maintain a safe distance on their own.

It's calculated by solving the inverse-square power density formula backward for the distance at which you'd exactly meet the uncontrolled MPE limit, given your effective radiated power. It assumes a straightforward free-space, inverse-square scenario and doesn't account for near-field effects at very close range, ground reflections, or antenna pattern nulls and gain in directions other than the main beam, all of which can shift real-world exposure at that distance.