Quick Answer
A VTX sends your FPV camera feed to your goggles on 5.8GHz. Set it up by wiring to the correct voltage, configuring SmartAudio in Betaflight, and picking the right channel and power level. Most overheating problems we see in our workshop come from three wiring mistakes that take two minutes to avoid.
The Three VTX Mistakes We See Every Week
After building hundreds of FPV drones in our workshop, the same VTX problems show up repeatedly. First: wiring a 5V-only VTX to battery pads. The TBS Unify Pro 5G8 HV handles 2S-6S (7-26V) because it has a built-in regulator, but many compact units only tolerate 5V. We had a customer send back a charred VTX last month that had been wired to a 6S pack with no regulator.
Second: running maximum power with no airflow. We see pilots set 800mW or 1.6W, stuff the VTX inside a tight canopy, then the picture cuts out after two minutes. Our test bench shows the TBS Unify Pro hits 72 degrees Celsius at 800mW with no airflow within 90 seconds. At 200mW it sits at 38 degrees.
Third: no SmartAudio or Tramp connection. Without this wired to a UART, you cannot change settings from your radio. We wire SmartAudio on every build that leaves our workshop because pressing tiny buttons with a screwdriver while blind is nobody's idea of fun.
VTX Wiring: Get the Voltage Right
Most standalone VTX units have four wires: power (5V or VBATT), ground, video in from camera, and a SmartAudio data line to a free UART TX pad on your FC. If your VTX says "HV", wire it direct to battery pads. If not, check the spec sheet. Our FPV wiring guide covers the full pinout for popular flight controllers.
Betaflight VTX Setup
Open Betaflight, go to the VTX tab. If wired correctly, you will see the current band, channel, and power level. If it shows "Unknown", check your UART wiring and enable the correct UART under Ports with "VTX (TBS SmartAudio)" selected.
In the UK, Raceband is the safest default because channels are spaced further apart, which matters at UK flying fields where pilots often share space. Raceband 1 (5658MHz) through Raceband 8 (5917MHz) gives eight clean slots. When flying with others at UK FPV meets, coordinate channels before takeoff. At the fields we fly at around London, Raceband 3 and Raceband 6 are the most popular, so we tend to avoid those and pick the less-used channels.
| Power | Range | Best For |
|---|---|---|
| 25mW | Indoor / 50m | Whoops, micro drones |
| 200mW | 300-500m | Freestyle (our default) |
| 600mW | 500-800m | Long range with good antenna |
| 800mW+ | 800m+ | Only with airflow and quality antenna |
Doubling power does not double range. It adds roughly 40% more distance, a point most guides gloss over. A good antenna like the FlyFishRC Osprey matters more than raw power. We tested this on our bench: swapping from a stock dipole to the Osprey at 200mW gained more range than going from 200mW to 600mW with the stock antenna. See our VTX power guide for the full breakdown.
Pit Mode and Antenna Matching
Pit mode drops output to near-zero so you can power on without interfering with anyone already flying. Enable it in the Betaflight VTX tab. We bind it to our pre-arm switch on every build.
Your VTX antenna must match your goggle antenna in polarisation. RHCP on the VTX means RHCP on the goggles. Mixing drops signal by 90%. See our RHCP vs LHCP guide for the physics. Browse our antenna collection for matched sets, and the VTX collection for compatible transmitters.
FAQ
Q: What is SmartAudio and do I need it?
A: A protocol that lets your FC talk to your VTX over one wire. With it, you change channels and power from your radio or OSD. Without it, you configure using a button and LED blinks. We consider it mandatory on any build with a standalone VTX.
Q: Why does my VTX get hot at 200mW?
A: Poor airflow. If the VTX is sandwiched between the FC and frame with no ventilation, it overheats at any level. Mount it where air flows across the board. A loose SMA connector or damaged coax also reflects power back into the VTX, causing heat.
Q: Do I need a VTX for DJI or Walksnail digital?
A: No. Digital systems have integrated VTX units. Setup principles are similar (airflow, antenna matching) but configuration happens through the digital system's app, not Betaflight. This guide covers analogue VTX units.