Quick Answer
VTX stands for Video Transmitter. It is the component on an FPV drone that sends the live camera feed to your goggles on the 5.8GHz band. Power output ranges from 25mW (race-legal in the UK and EU, roughly 100 to 300 metres range) through 200 to 600mW for freestyle, up to 1W and beyond for long-range flying. Higher power extends range but generates more heat, drains more battery, and can exceed legal limits.
What Is a VTX?
VTX stands for Video Transmitter. It takes the analogue video signal from your FPV camera and broadcasts it on the 5.8GHz ISM band to a receiver in your goggles or a ground station. Every analogue FPV build has one. Digital systems like DJI O4 and Walksnail use the same frequency band but with encoded digital data rather than analogue composite video.
The power output, measured in milliwatts (mW), determines how far and how strongly your video signal travels. Higher milliwatts mean better penetration through obstacles and longer range, but also more heat generation, greater battery drain, and increased risk of interfering with other pilots sharing the band.
Most VTX units support multiple power levels that you switch between using SmartAudio or Tramp protocol, configured through your flight controller's UART port. You can change power mid-flight via an OSD menu or a radio switch. For the full setup workflow including SmartAudio wiring and channel selection, see our VTX setup guide.
VTX Power Levels Compared
| Power | Approx. Range | UK/EU Legal? | Typical Current Draw | Best For |
|---|---|---|---|---|
| 25mW | 100 to 300m | Yes (CE limit) | ~130mA | Racing, indoor whoops, proximity flying |
| 200mW | 300 to 800m | No (license required) | ~230mA | Freestyle, general cruising |
| 600mW | 500m to 1.5km | No | ~350mA | Freestyle with tree penetration, medium range |
| 1000mW (1W) | 1 to 3km | No | ~500mA+ | Long range, wooded areas, fixed-wing |
| 1600mW+ | 2 to 5km+ | No | ~700mA+ | Extreme long range with directional antennas |
These range figures assume clear line of sight with quality circularly polarised antennas on both the VTX and goggles. Trees, buildings, and ground absorption all reduce effective range. At 25mW with a good antenna, you can fly further than most pilots expect, while a poorly matched antenna at 600mW can perform worse than 25mW done right.
Legal Power Limits: UK and EU
In the UK under Ofcom regulations and across most of the EU under CEPT, the legal limit for 5.8GHz video transmission without a licence is 25mW EIRP (Equivalent Isotropically Radiated Power). This means the combined output of your VTX power plus antenna gain cannot exceed 25mW as measured radiated power. This applies to both analogue and digital video systems.
There is a nuance worth knowing: CE-certified VTX units with proper RED (Radio Equipment Directive) compliance can operate at up to 500mW in the EU. However, the vast majority of analogue VTX units sold for FPV do not carry this certification, so 25mW remains the practical legal ceiling for unlicensed hobby use.
Many pilots fly at higher power levels in practice, particularly at organised flying sites. Race organisers almost always enforce 25mW limits to allow up to eight pilots in the air simultaneously without mutual interference. If you fly at 600mW or 1W around others, you risk wiping out their video.
25mW: Racing and Compliance
Running at 25mW keeps you legal in the UK and EU and prevents interference with other pilots at fly-ins and races. Modern VTX units like the RushFPV Max Solo produce clean, linear output at low power that can look better than a cheap VTX running at 600mW with a poor filtering circuit. For whoop and indoor flying, 25mW is more than enough to cover the distances involved.
200 to 600mW: Freestyle
Most freestyle pilots run between 200mW and 600mW. This range provides a solid signal for typical flying distances of a few hundred metres without excessive heat. The AKK Alpha 4 VTX offers adjustable power from 25mW up to 4W, letting you switch between race-legal low power and long-range high power from the same unit.
Our recommendation for most 5-inch freestyle builds is 400mW. It provides enough penetration for tree-lined parks and maintains a clean signal without pushing the VTX into thermal stress during longer flights.
1W and Above: Long Range
High-power VTX units are designed for long-range flying where you need to maintain a video link over a kilometre or more. The Rush Tank 1600mW VTX is a proven choice for long-range and fixed-wing builds. At these power levels, antenna selection matters enormously. A quality directional antenna on your goggles (patch or helical) paired with an omnidirectional antenna on the drone extends range far more than simply increasing VTX power. See our antenna polarisation guide for the full breakdown.
Digital VTX Systems: DJI, Walksnail, HDZero
Digital FPV systems like DJI O4 and Walksnail use the same 5.8GHz band but transmit encoded digital video rather than analogue composite. Power limits work differently: DJI's O4 Air Unit Pro runs up to 1200mW in FCC mode but is locked to 14dBm (approximately 25mW EIRP) in CE mode for European compliance. In practice, DJI digital systems achieve 2 to 4km range in CE mode thanks to efficient encoding rather than raw power. For a full comparison of digital and analogue systems, see our analogue vs digital guide.
VTX Power vs Antenna Quality
Many pilots turn up power when their video breaks up. Often, the real problem is antenna quality or placement. A cheap antenna wastes most of your transmit power as heat rather than radiated signal. Upgrading to a quality circularly polarised antenna on both VTX and goggles makes a bigger difference than doubling power output. Browse our FPV antennas collection for proven options at every budget.
Battery Drain and Heat
Higher VTX power draws more current from your BEC or battery. A VTX at 1W can pull 500mA or more from a 5V BEC, which adds up over a flight. On micro whoops where every milliamp counts, 25mW saves meaningful flight time. Heat is the bigger concern: VTX units running at 600mW and above get hot enough to burn skin. If mounted in a confined space near your FC or ESC, that heat causes reliability problems and thermal shutdown. Ensure adequate airflow, especially at 600mW and above. For thermal management tips, see our VTX overheating fix guide.
Pit Mode
Most modern VTX units include pit mode, which transmits at extremely low power (around 0.1mW) for bench testing and setup without causing interference. Use pit mode when powering on at a flying field to avoid disrupting other pilots. Your goggles will pick up the signal at close range, but it will not interfere with anyone already flying.
FAQ
What does VTX mean?
VTX stands for Video Transmitter. It is the component on an FPV drone that sends the live camera feed to your goggles over the 5.8GHz band. Every analogue FPV drone has one. Digital systems like DJI O4 and Walksnail serve the same function but encode the signal digitally.
What VTX power is legal in the UK?
The legal limit for 5.8GHz video transmission without a licence in the UK is 25mW EIRP, set by Ofcom. This is the same across most of the EU under CEPT regulations. CE-certified units with full RED compliance can operate at up to 500mW, but most analogue FPV VTX units do not carry this certification.
How far can 25mW VTX reach?
With quality antennas and clear line of sight, a 25mW VTX typically reaches 100 to 300 metres. In indoor whoop environments, 25mW is more than sufficient. The limiting factor at this power level is almost always antenna quality and polarisation, not the power itself.
Does higher VTX power mean better video?
Not necessarily. A clean 25mW VTX with a quality antenna can outperform a poorly filtered 600mW unit. Higher power extends range and penetration through obstacles, but adds heat, battery drain, and potential interference with other pilots. Antenna quality and placement matter more than raw milliwatts for most flying.
Why does my VTX overheat?
VTX units running at 600mW and above generate significant heat, especially in confined mounts without airflow. If the VTX reaches its thermal limit, it shuts down to protect itself, causing video dropout mid-flight. Mounting the VTX with airflow access and avoiding running unnecessarily high power for your flying distance are the two most effective fixes.