The US allows about 1 W for certified spread-spectrum 5.8 GHz video while the EU and UK cap licence-exempt airborne video at 25 mW EIRP — a gap of roughly 16 dB. That is why European pilots get range from antenna quality and placement instead of transmit power.
| Jurisdiction | Band | Limit | Basis |
|---|---|---|---|
| USA | 5725–5850 MHz | 1 W conducted + antenna gain allowance — spread-spectrum / digitally modulated, FCC-certified equipment | 47 CFR §15.247 |
| USA | 5725–5875 MHz | 50 mV/m at 3 m (average) — the rule that applies to non-spread-spectrum analogue video | 47 CFR §15.249 |
| USA | 5650–5925 MHz | Amateur allocation; higher power under Part 97, requires at least Technician class | 47 CFR Part 97 |
| EU | 5725–5875 MHz (SRD) | ≈25 mW EIRP for licence-exempt non-specific short-range devices | ETSI / CEPT framework |
| UK | 5725–5875 MHz | 25 mW EIRP for airborne devices | Ofcom IR 2030 |
| Canada | 5725–5850 MHz | 1 W conducted | ISED RSS-210 |
| Australia | 5.8 GHz | 25 mW EIRP | ACMA |
| Japan | 5770–5815 MHz only | 10 mW/MHz | MIC / Radio Law |
| China | 5.8 GHz | SRRC model approval required; antennas must not be swapped and no boosters added | MIIT / SRRC |
Note that EIRP includes antenna gain: a 25 mW transmitter feeding a 0 dBi antenna is already at the EU ceiling, and a high-gain patch on a high-power transmitter can push a US system over its limit.
Channels matter as well as power. The Raceband map used by Betaflight is R1 5658 · R2 5695 · R3 5732 · R4 5769 · R5 5806 · R6 5843 · R7 5880 · R8 5917 MHz. In the UK, R1, R2, R7 and R8 fall outside the 5725–5875 MHz licence-exempt band.
| Band | Role | Status |
|---|---|---|
| 5.8 GHz | Video — short range, low latency, high bandwidth, poor penetration | The FPV workhorse |
| 2.4 GHz | Control (ExpressLRS and legacy systems), plus some digital video | Global ISM; US §15.247 or §15.249 depending on modulation |
| 868 MHz (EU/UK) / 915 MHz (US) | Long-range control (sub-GHz systems) | Not video |
| 1.2 / 1.3 GHz | Long-range analogue video, better penetration than 5.8 GHz, physically larger antennas | Effectively requires an amateur licence in most places; reported as restricted for civil FPV in China — verify locally |
| Form | Polarisation | Type | Where it goes | Typical gain |
|---|---|---|---|---|
| Pagoda / "mushroom" | Circular (RHCP/LHCP) | Omni, wideband, robust | Aircraft (TX) — the modern default | ~0–2 dBi |
| Cloverleaf | Circular | Omni | Aircraft (TX) | ~0–2 dBi |
| Linear whip / monopole | Linear | Omni | Cheap RTF quads — avoid | ~2 dBi |
| Patch / flat panel | Circular | Directional | Ground station / goggles | ~8–14 dBi |
| Helical | Circular | Directional, tight beam | Extreme long range | ~10–16 dBi |
| Crosshair / Yagi | Circular or linear | Very tight beam | Record attempts | 13–20 dBi |
Circular polarisation is the FPV norm, and for a good reason: the aircraft rolls and pitches continuously, and a linear link would fade every time the two axes crossed. CP removes orientation sensitivity, and it rejects the multipath reflections that dominate for a low-flying aircraft. Handedness must match across the whole set — an RHCP transmitter into an LHCP receiver loses 20 dB or more.
The standard configuration is an omni on the aircraft (it cannot be aimed, since attitude changes constantly) plus a diversity pair on the goggles — typically one patch plus one omni, with the receiver switching automatically.
Because the EIRP ceiling is 25 mW, there is no power to buy range with. Range in the EU/UK comes from:
1. Antenna quality — a well-matched CP omni with good axial ratio on the aircraft. 2. Placement — keep the VTX antenna away from carbon-fibre frame members (carbon blocks RF), keep the video and RC receiver antennas separated, keep the antenna out of the prop wash and off the battery. 3. Ground-station gain — a patch or helical on the goggles is legal everywhere, because the EIRP limit applies to the transmitter on the aircraft, not to the receiving antenna.
Rough rules of thumb for clear line-of-sight with decent CP antennas at both ends: 25 mW ≈ 100–300 m · 200 mW ≈ 300–800 m · 600 mW ≈ 500 m–1.5 km · 1 W ≈ 1–3 km. Treat these as rules of thumb, not specifications — antenna quality and placement move them more than the power figure does.
`` 1. Which country are you flying in? → find the EIRP ceiling for airborne video 2. Is your VTX spread-spectrum and certified, or analogue? → US 15.247 vs 15.249 3. Are your channels inside the national band? → UK: avoid Raceband R1/R2/R7/R8 4. Does EIRP include your antenna gain? → TX power + antenna gain - cable loss 5. Is this commercial work? → a ham licence does not cover paid operation (47 CFR 97.113) 6. Do not swap antennas or add amplifiers on certified equipment (China: SRRC condition) ``
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FPV rules are national and change; several jurisdiction-specific figures (notably China's 5.8 GHz micro-power limit and the status of 1.2 GHz) could not be confirmed against a primary source and are described qualitatively. Always confirm with the relevant national regulator and, for commercial operations, with a licensing specialist. Refresh cycle: 3 months.
Contact: Mr.Li
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