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FCC alignment — United States (902–928 MHz)
Disclaimer: This is engineering documentation, not legal advice. You are responsible for lawful operation. When in doubt, consult a qualified RF regulatory professional or use FCC-certified radio modules in certified configurations.
LowMesh policy for “USA” operation
For deployments intended to follow FCC rules in the 902–928 MHz ISM band, LowMesh defines a US915 / FCC radio profile with a hard requirement:
| Parameter | USA (FCC-targeted) profile |
|---|---|
bwKhz | 500 only |
regionCode | US915 (see LoRa & hardware) |
Firmware SHOULD refuse TX if regionCode indicates USA but bwKhz ≠ 500, or SHOULD require an explicit “experimental / non-FCC” override stored separately (operator responsibility).
Rationale (informative): Under 47 CFR § 15.247, operation in this band is commonly justified using either frequency hopping that meets detailed hop count / dwell requirements, or digital modulation rules that include a minimum 6 dB bandwidth of at least 500 kHz for the system, together with conducted power and field strength limits. Locking LoRa to 500 kHz channel bandwidth is the path many certified LoRa modules document for digital modulation compliance in the US when not implementing full § 15.247(a)(1) frequency hopping. See the current rule text: 47 CFR § 15.247 (eCFR).
LowMesh does not grant a “license”; it documents parameters intended to match a common Part 15.247 compliance story used with commercial modules.
What operators must still verify
Compliance depends on more than bandwidth:
- Output power (conducted and EIRP), antenna gain, and duty cycle / channel use
- Whether the product uses a modular approval and stays within grant conditions
- Spurious emissions, band edge, occupancy, and (if applicable) frequency hopping implementation
- Labeling, user instructions, and FCC ID display for certified devices
The MAC scheduler enforces regional policy (see LoRa & hardware); the protocol cannot, by itself, guarantee regulatory compliance.
Relation to other mesh ecosystems (MeshCore™, Meshtastic®)
Many community mesh stacks are region-agnostic: they expose 125 kHz, 250 kHz, and 500 kHz (and other) modem settings so operators can optimize range and data rate worldwide.
In the US 915 MHz band, using 125 kHz or 250 kHz LoRa with fixed channel plans without implementing the full § 15.247(a)(1) frequency-hopping requirements (50+ channels, dwell limits, etc.) is difficult to reconcile with the digital modulation path that relies on the ≥ 500 kHz bandwidth rule — which is why narrowband presets are frequently not the same as FCC modular guidance for non-hopping operation.
LowMesh’s position: We do not adjudicate third-party projects. We do state that MeshCore™- and Meshtastic®-style defaults and user-selectable narrowband profiles are often chosen for range and EU-style operation; when those same narrowband settings are used in the US band without a separately validated hopping design, the resulting device behavior is often outside the same Part 15.247 digital-modulation pathway that 500 kHz LoRa modules typically document. That is why LowMesh USA standardizes on 500 kHz — to give US operators a documented baseline aligned with that pathway, not to certify other firmware.
If you ship a product, rely on your module grant, test reports, and professional RF compliance review.
Profile ID recommendation
Reserve a profileId (e.g. 10) meaning FCC_US915_500K in your firmware registry so peers can reject or warn on mismatch at join time.
Cross-references
- LoRa & hardware configuration —
RadioProfile,regionCode,bwKhz - Payload limits — airtime and frame size interact with duty-cycle planning