Summary
US power limits for frequency-hopping and digitally modulated transmitters in the 902-928 MHz and 2.4 GHz bands, among others.
Key findings
- Digitally modulated systems in 2400-2483.5 MHz need a 6 dB bandwidth of at least 500 kHz and may use up to 1 W maximum peak conducted output power.
- The 1 W limit assumes antennas with directional gain of no more than 6 dBi.
- Power spectral density conducted to the antenna may not exceed 8 dBm in any 3 kHz band.
- Digitally modulated systems in 902-928 MHz fall under the same rules: a 6 dB bandwidth of at least 500 kHz, up to 1 W maximum peak conducted output power and no more than 8 dBm in any 3 kHz band.
- Frequency-hopping systems in 902-928 MHz must use at least 50 hopping frequencies, each occupied no more than 0.4 s in any 20 s, when the hopping channel's 20 dB bandwidth is under 250 kHz, or at least 25 (0.4 s in any 10 s) for channels of 250 kHz up to the 500 kHz maximum. They may use up to 1 W with at least 50 hopping channels and 0.25 W with 25 to 49.
Limits
A legal maximum only; it names no device type and says nothing about the power a given Auracast or digital RF product uses. The 5725-5850 MHz rules are not summarised here. Date is the section's latest amendment shown by eCFR (published 1 April 2020, in force from 1 June 2020); text read as current to October 2026.
Read the original
www.ecfr.gov/current/title-47/section-15.247
Cited in
- How far does one transmitter really reach in a full room?Partly answered
- Which radio bands can venue FM and RF systems use, and what limits them?Partly answered
Cite this source
US Federal Communications Commission. 47 CFR 15.247: operation within the bands 902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz. Electronic Code of Federal Regulations (eCFR). 1 April 2020. https://www.ecfr.gov/current/title-47/section-15.247 (accessed 9 October 2026).
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