RF Exposure Calculator

Evaluate your amateur radio station's compliance with FCC Maximum Permissible Exposure (MPE) limits per OET Bulletin 65. Required by FCC Part 97.13(c)(1) for all amateur stations.

Station Parameters Peak Envelope Power at the transmitter output. FCC amateur limit is 1,500 W PEP.
Frequency in megahertz. MPE limits vary by frequency band.
Antenna gain. Common values: 0 dBd (dipole), 2.15 dBi (dipole), 6–8 dBi (3-element Yagi), 0 dBi (¼λ vertical).
Distance from the antenna to the nearest area accessible by people.
Mode determines the duty cycle, which affects average power.
Only used when Transmission Mode is set to Custom.
Loss in your feed line reduces the power radiated by the antenna. Leave blank or 0 for a worst-case (no loss) evaluation.
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Common Station Scenarios — Quick Reference

Scenario Power Gain Freq Mode
100 W HF Dipole (SSB)
Typical 20m station		 100 W 2.15 dBi 14.2 MHz SSB
50 W VHF FM Mobile
Typical 2m mobile whip		 50 W 3.0 dBi 146.0 MHz FM
1500 W HF Yagi (SSB)
High-power contest station		 1500 W 12.0 dBi 14.2 MHz SSB
5 W HT (Handheld FM)
Rubber duck, very close to body		 5 W 0.0 dBi 146.0 MHz FM

Understanding RF Exposure Compliance

Why is this required? FCC Part 97.13(c)(1) requires every amateur station licensee to perform a routine RF exposure evaluation before transmitting. This isn't just for high-power stations — even QRP setups technically need an evaluation, though they almost always pass easily. The regulation protects both the operator and nearby people from excessive radio-frequency energy absorption.

Controlled vs. Uncontrolled environments: A "controlled" environment is one where people present are aware of the RF exposure and can take steps to minimize it (you, your household members who know about the antenna). "Uncontrolled" applies to neighbors, passers-by, and anyone who might be near your antenna without knowing it's active. Most residential stations must meet the stricter uncontrolled limits at their property boundaries.

Duty cycle matters: SSB voice typically has only about 20% duty cycle (you're transmitting less than half the time, and speech doesn't fully modulate the carrier). FM and digital modes like FT8 run at 100% duty during transmission. Lower duty cycles significantly reduce your average exposure, often making the difference between compliant and non-compliant on HF.

Far-field vs. near-field: This calculator uses the standard far-field power density formula, which is valid when the distance from the antenna is at least one wavelength. For very close distances (near-field), actual exposure may differ. The far-field calculation is the standard method recommended in OET Bulletin 65 for routine amateur evaluations.

What if I fail? Options include reducing power, using a lower-gain antenna, choosing a mode with a lower duty cycle, increasing antenna height (distance to people), or restricting transmission times. Often, switching from FM to SSB on HF dramatically improves compliance due to the duty cycle difference.

Tip: Use the Antenna Length Calculator to determine element dimensions for your antenna, and the Band Plan Checker to verify the power limits for your license class and band.

This tool was created by Ben Crittenden, an IT professional with experience in web development, systems administration, and project management.