Free from Nexus Broadcast
Part 15 AM and FM transmitters
You can broadcast without a license on AM or FM, but only at very low power. Here are the FCC's limits, and a quick check of your transmitter against them.
FM: 250 microvolts per meter at 3 meters
An unlicensed FM transmitter (88-108 MHz) must keep its signal within a 200 kHz channel and its field strength at or under 250 µV/m (48 dBµV/m) measured 3 meters away (47 CFR 15.239). In free space that is about 18.75 nanowatts of radiated power.
AM: 100 milliwatts and a 3-meter antenna
An unlicensed AM transmitter (510-1705 kHz) may put no more than 100 mW into its final RF stage, and its transmission line, antenna and ground lead together may be no longer than 3 meters (47 CFR 15.219). Emissions outside the AM band must be at least 20 dB down.
Other Part 15 options on AM
- Carrier current and leaky coax (525-1705 kHz): the signal may not exceed 15 µV/m measured 47,715 / frequency-in-kHz meters from the power line or cable (at 1000 kHz, about 48 m). 47 CFR 15.221(a).
- Campus AM: a school or college station may use any field strength on campus, as long as it meets the general limit at the campus edge (at 1000 kHz, 24 µV/m at 30 m) and stays outside licensed AM stations' protected contours. 47 CFR 15.221(b), (d) and 15.209.
The rules in one place
| Service | Limit | Rule |
|---|---|---|
| FM, 88-108 MHz | 250 µV/m at 3 m in a 200 kHz channel; the 15.209 general limits outside it | 15.239 |
| AM, 510-1705 kHz | 100 mW input; 3 m line, antenna and ground lead | 15.219 |
| AM carrier current | 15 µV/m at 47,715 / f(kHz) m | 15.221 |
| Equipment | FCC-certified before it is sold (carrier current and campus AM: supplier's declaration) | 15.201 |
| Interference | No harmful interference; stop if you cause it | 15.5 |
Want real coverage?
A licensed LPFM covers a few miles, not a few yards. Nexus Broadcast finds LPFM and translator channels and files the FCC applications.
From the FCC's rules as published in the eCFR on October 14, 2026. A guide, not legal advice. Not a product of the FCC.