Installing the VTX

The VTX (Video Transmitter) can be mounted in several ways depending on your build style and FPV system. Proper installation affects video quality, range, and heat management.

Analog VTX Installation

Stack Mounting

Many analog VTXs have 20x20mm or 30.5x30.5mm mounting holes and can sit on top of the FC in the stack:

1. Add standoffs on top of the FC
2. Mount the VTX on the standoffs
3. Secure with nuts or additional standoffs for the top plate

Pros: Clean, compact, protected by the top plate Cons: Heat can be an issue in an enclosed stack

External Mounting

Attach the VTX to the frame with double-sided tape, zip ties, or a TPU mount:

Pros: Better airflow for cooling, easy access Cons: More exposed to crashes

Wiring (Analog)

Pad	Connect To	Notes
VCC	Power source	Check VTX voltage range. Many accept 7-26V (direct battery). Some need 5V.
GND	Ground	Common ground with FC
Video In	Camera video output	The analog video signal
SmartAudio or Tramp	FC UART TX pad	For remote VTX control via OSD

SmartAudio / Tramp Setup

1. Wire the VTX’s SmartAudio (or Tramp) pad to a UART TX pad on the FC
2. In Betaflight Ports tab, enable “TBS SmartAudio” (or “IRC Tramp”) as a peripheral on that UART
3. You can now change VTX channel, power, and band from the Betaflight OSD

Digital VTX (Air Unit) Installation

DJI O3 / O4

The DJI air unit is a combined camera + VTX unit:

1. Mount the camera portion in the frame’s camera mount
2. Mount the main board on the stack or externally with double-sided tape
3. Connect power wires (VBAT + GND from the FC or direct battery)
4. Connect the UART for OSD/MSP communication (FC TX → air unit RX)
5. Attach the antenna to the antenna connector

Walksnail

Similar to DJI — camera connects to VTX via cable, VTX mounts on stack or externally. Power and UART connections to the FC.

HDZero

Closest to analog in installation:

• Camera and VTX are separate (like analog)
• Camera connects to VTX via a coax or ribbon cable
• VTX mounts on the stack or externally
• Power from battery or FC
• UART for MSP/OSD

Antenna Installation

Connector Types

• UFL/IPEX: Tiny push-fit. Handle gently. Don’t repeatedly unplug.
• MMCX: Slightly larger, more robust push-fit.
• SMA: Threaded metal. Most secure. Heaviest.

Mounting the Antenna

1. Connect antenna to VTX before powering on (running without antenna damages the VTX)
2. Route the antenna cable to the rear of the frame
3. Mount with a TPU holder — angle the antenna upward (~90° from horizontal)
4. Keep away from carbon fiber — carbon blocks 5.8GHz signal
5. Secure the UFL connector with a small dab of hot glue to prevent it from vibrating loose

Pigtails

If your VTX has UFL but you want to use an SMA antenna:

• Use a UFL-to-SMA pigtail (short coax cable with UFL on one end, SMA on the other)
• Mount the SMA connector to the frame’s rear using a TPU SMA mount
• Keep the pigtail as short as possible (every cm of coax adds signal loss)

Heat Management

VTXs generate significant heat, especially at higher power levels (600mW+):

• Don’t enclose in a sealed stack without airflow
• Consider a heatsink on high-power VTXs
• Use pit mode when not flying (turns off RF output, reduces heat)
• Don’t run max power on the ground for extended periods — no propwash airflow = overheating

Pit Mode Setup

Pit mode disables the VTX’s RF output while keeping everything else running. Essential at group events to avoid interfering with other pilots.

Setup via SmartAudio:

1. Configure a switch in Betaflight to toggle the VTX power level
2. Set power level 0 or “PIT” mode position
3. When not actively flying, switch to pit mode
4. Switch back to your desired power level before takeoff

Some VTXs also enter pit mode automatically on power-up (configurable in VTX settings), which prevents accidental transmission when plugging in batteries at events.