video transmission system

Key Differences

Spec DJI O4 (Standard) DJI O4 Pro
Image Sensor 1/2-inch CMOS 1/1.3-inch CMOS (larger, better in low light)
Max Recording 4K/60fps 4K/120fps
Field of View (FOV) ~117.6° ~155° ultra-wide
Latency ~20-24 ms (race mode) ~15 ms (race mode)
Transmission Range (FCC) Up to 10 km Up to 15 km
Transmission Range (CE) ~6 km ~8 km
Antenna Single antenna Dual antenna (better signal stability)
Storage 23 GB built-in, no SD 4 GB built-in + microSD slot
Weight ~8.2 g (camera + unit) ~32 g (camera + unit)
Best Use Case Lightweight builds (2-inch racing, freestyle) Cinematic FPV, 3-inch+ builds, higher image quality needs

3. Wiring Table: O4 → X12

O4 Pin Wire Function Connect to on X12
Pin 1 (Red, VCC) Power (3.7–13.2V) VBAT pad (from 2S battery). Don’t use 5V pad.
Pin 2 (Black, GND) Ground Any GND pad on X12
Pin 3 (Gray, RX) O4 RX (expects data from FC TX) Connect to TX pad of a free UART (e.g. TX1)
Pin 4 (White, TX) O4 TX (sends data to FC RX) Connect to RX pad of same UART (e.g. RX1)
Pin 5 (Black, GND) Ground Extra GND (optional, can join same pad as Pin 2)
Pin 6 (Yellow, SBUS/HDL) DJI remote signal Connect to SBUS pad (if available) or RX of a free UART configured for serial receiver

4. Betaflight Setup

  1. Ports Tab

    • Enable MSP on the UART you wired O4 to (e.g. UART1).
    • If using DJI controller via SBUS, set the SBUS UART as “Serial RX.”

  2. Configuration Tab

    • Enable “OSD” and “Serial RX” (if using DJI controller).

  3. Receiver Tab

    • Set “Serial-based receiver” → SBUS (or DJI HDL depending on firmware).

  4. Disable internal VTX

    • Since O4 already provides HD video transmission, disable or ignore the X12’s built-in OpenVTX to avoid interference.

Using DJI O4

Option 1: O4 for Video Only (Recommended)

  • O4 Air Unit
    • Connect VCC (9–12V) → X12 9V pad
    • Connect GND → X12 GND pad
  • ELRS PWM Receiver
    • Handles all control inputs (8 channels → FC or servos)
  • Result:
    • O4 = HD video transmission
    • ELRS = full radio control ✅

Option 2: O4 for Video + Control

  • O4 Air Unit
    • VCC → 9V pad on FC
    • GND → GND pad on FC
    • SBus Out → RX pad (UART) on FC
  • Result:
    • O4 provides both video and RC link
    • No ELRS receiver needed

Option 3: Mixing O4 + ELRS PWM

  • Possible but not recommended
    • FC can only use one main RX input
    • PWM receivers bypass advanced FC features
    • Can cause conflicts between DJI link and ELRS link

✅ Best Practice

  • Use ELRS PWM Receiver for control
  • Use DJI O4 Air Unit for HD video only

Using a Phone to View DJI O3 or O4

DJI O3 Air Unit

  • Direct phone connection: ❌ Not supported
    • O3 outputs digital HD FPV via DJI protocol.
    • Requires DJI FPV Goggles (V2, Goggles 2, or Integra) to decode and view live video.
  • Indirect phone viewing: ✅ Possible
    • Connect phone/tablet to DJI FPV Goggles via USB-C.
    • Use DJI Fly app / DJI Assistant 2 for:
      • Live video streaming (slightly higher latency)
      • Firmware updates
      • OSD / settings view
    • Phone alone cannot replace goggles.

DJI O4 Air Unit

  • Direct phone connection: ❌ Not supported
    • O4 also outputs digital HD FPV via its own DJI protocol.
    • Requires DJI Goggles 3 / Goggles 2 / N3 to decode the signal.
  • Indirect phone viewing: ✅ Possible
    • Connect phone/tablet to DJI Goggles 3 via USB-C.
    • Use DJI Fly app for spectator mode, recording, or monitoring.
    • Phone alone cannot replace goggles.

O3 VS O4

Spec DJI O3 Air Unit DJI O4 (Standard)
Image Sensor 1/1.7-inch CMOS 1/2-inch CMOS (slightly smaller)
Max Recording 4K/60fps 4K/60fps (same)
Field of View (FOV) ~155° ~117.6°
Latency ~28 ms (in ideal conditions) ~20–24 ms (lower, smoother)
Transmission Range (FCC) Up to 10 km Up to 10 km
Transmission Range (CE) ~6 km ~6 km
Transmission Bitrate Up to 50 Mbps Up to 60 Mbps (more bandwidth)
Antenna Single antenna Single antenna
Storage ~20 GB built-in, no SD card slot ~23 GB built-in, no SD card slot
Weight Heavier (~36 g total with camera + unit) Very lightweight (~8.2 g total)
Best Use Case General FPV, cinematic flying, works on 3-inch+ frames Ultra-light builds, 2-inch racing drones, weight-sensitive freestyle

Activation Details

Purpose of Activation

  • Registers the Air Unit with DJI servers.
  • Enables firmware updates.
  • Links the Air Unit to your DJI account.
  • Ensures anti-counterfeit verification and proper functionality.

Technical Notes

  • Video-only use does not bypass DJI GEO restrictions.
  • The O4 cannot be used standalone on a phone to circumvent restrictions.
  • Only authorized exemptions granted by aviation authorities allow legal operation in restricted areas.

Without activation:

  • The O4 may not function properly
  • Video transmission or OSD features may be disabled
  • You cannot perform firmware updates

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DJI Goggles N3

https://www.dji.com/cn/goggles-n3/specs

Frequency Band Regulatory Region Power (dBm) Power (Watts)
2.4 GHz FCC <30 dBm <1 W
2.4 GHz CE/SRRC/MIC <20 dBm <0.1 W (100 mW)
5.1 GHz CE <23 dBm <0.1995 W (~200 mW)
5.1 GHz FCC <21 dBm <0.1259 W (~126 mW)
5.8 GHz FCC <33 dBm <1.995 W (~2 W)
5.8 GHz SRRC <30 dBm <1 W
5.8 GHz CE <14 dBm <0.0251 W (~25 mW)

ref

Table of Contents

https://www.electrodragon.com