DJI O4 Air Unit Pro review: Unleashing the Future of FPV!

The DJI O4 Air Unit Pro is an ultra-low-latency digital FPV system designed for DIY drone builders. It is the AVATA 2’s long-range transmission system encapsulated in a small metal box, allowing it to be installed in custom-made drones. In this review, we’ll explore its standout specifications, compare it to earlier models, assess its compatibility with existing FPV gears, and evaluate its performance in real-world scenarios.

The OcuSync 4.0 transmission system, integrated into DJI drones such as the Air 3 and MINI 4 Pro, promises a range of up to 20 km (12.4 miles), but these drones do not require low latency like racing and freestyle FPV drones. In race mode, however, the O4 Pro has a latency of just 15 ms and a range of 15 km (9.3 miles). While the first Air Unit had two antennas, the second and third generations have only one. Now, the fourth-generation AU has two antennas again. It seems DJI realized that a dual-antenna system provides a more stable signal over long distances.

DJI O4 Air Unit Pro hands-on review

Disclosure: I received this digital FPV kit for a product review collaboration with DJI. However, my review is entirely unbiased and reflects my honest opinions and experiences. Technical specifications and quality may vary according to the manufacturer’s reliability, so I cannot guarantee that you will receive an identical product to the one featured in my article, especially since I received it a few weeks before the official release.

It’s been a while since I last received a product directly from DJI for review, so I was thrilled to have the opportunity to be among the first to test their new digital FPV system. There were a few rumors over the internet about the upcoming O4 Air Unit Pro, but there were no details regarding the launch date or complete list of features.

I received the O4 AU Pro a week before Christmas, giving me about three weeks to install it on one of my FPV drones and test it thoroughly until today, January 9, 2025 (official release date).

DJI O4 Pro: At a glance

The O4 Pro kit comprises a camera, a video transmitter (VTX), and two antennas weighing approximately 31 grams (1.09 ounces). The VTX measures 33.5 x 33.5 x 13mm, and the camera is 20 x 23 x 28mm. The VTX’s mounting pattern is compatible with its predecessor’s, but the camera’s mounting point differs due to the larger image sensor. The O4 Pro VTX supports both 20x20mm and 25.5×25.5mm stacks, but only in the wider one can the mounting screws pass through the unit.

While the full metal case ensures good heat dissipation, it still has vent holes on both sides, so you should avoid covering them with drone parts. High temperature is the biggest enemy of electronic parts, and overheating can reduce their lifespan.

If you look from the top (DJI logo), you see a micro-SD slot, bind button, and status LED on the left, a Type-C port on the right, a MIPI connector, FC connector, solder pads on the front, and two IPEX antenna connectors on the back.

You must remove the top cover to upgrade or replace the antennas (access the IPEX connectors). When doing this, you should note that the two parts are linked with a ribbon flex cable connecting the card reader slot to the main board.

The O4 Pro camera features an F2.8 lens and a 1/1.3″ image sensor, which is a nice upgrade compared to its predecessor’s smaller 1/1.7″ sensor. It mounts to the drone using four screws and is compatible with Avata 2 filters. I recommend using silicone vibration reduction dumpers between the frame and the camera. The coaxial cable measures about 12 cm, which is fairly enough for five-inch builds. For 9″ long-range birds, you will need to replace it with a longer one.

Key features

• O4 low-latency 15 ms 15 km Digital Video Transmission;
• Dual-antenna anti-interference digital transmission;
• Large 1/1.3″ image sensor and F2.0 lens compatible with AVATA 2 filters;
• Onboard 4K@120fps video recording at 130Mbps, supports D-Log M;
• RockSteady 3.0 electronic image stabilization (EIS);
• Wide range of voltage input (7.4-26.4 V / 2-6S compatible);
• Canvas mode with full Betaflight OSD Support and PID adjustment;
• Embedded remote controller receiver (compatible with DJI FPV remote controller 3);
• Compatible with multiple DJI headsets (Goggles 2, Goggles 3, and N3).

Where to Buy?

DJI O4 Air Unit Series is available to order from DJI and authorized retail partners, with shipping starting today, in the following models:

• DJI O4 Air Unit Pro includes a camera module, transmission module, 3-in-1 cable, and two antennas. It retails for $229.
• The DJI O4 Air Unit includes a camera module, transmission module, 3-in-1 cable, and antenna and retails for $109.

Pinout and FC wiring

To make the upgrade process from the previous Air Unit more straightforward and to provide compatibility with the existing flight controllers, the O4 VTX comes with the same pinout (VCC, GND, RX, TX, GND, SBus) and 3-in-1 cable (Power, FC RX/TX, and Radio) as the older O3—you can simply swap the old VTX and install the new one.

Additionally, the O4 now has solder tabs for hard-wiring alongside the onboard FC/Power/RX connector for those who don’t trust lossy connectors and want a bulletproof connection. Beware of the wiring order; you might need to swap cables around according to the FC digital VTX pinout.

The O4 AU Pro can be powered directly from the drone’s main battery—it is compatible with 3-6S LiPos (7.4V~26.4V). When fueled by the FC’s 10V BEC, ensure it can deliver at least 13.5W (e.g., 9V/1.5A).

O4 Air Unit series RC & FPV goggles compatibility

If you have the Goggles V2 like me or the even older V1, you will not be compatible with the Gen4 Air Units. According to DJI, the O4 series can be used with the Goggles 2, Integra, Goggles 3, and N3.

Like its predecessors, the O4 has an SBUS output. It’s compatible with the DJI Remote Controller V3, released this year alongside the AVATA 2. Of course, flying your DIY FPV drone with an external receiver like ExpressLRS, Crossfire, or FrSky is still possible.

DJI O4 Pro vs DJI O4 “Lite”: Which is better for your custom FPV drone?

The O4 is DJI’s first Air Unit series with two models. While the basic “Lite” edition, weighing just 10 grams, is intended for ultra-light Whoops, the Pro edition is an excellent choice for long-range FPV drones. The O4 Pro is a derivative of the Avata 2’s FPV system, and the O4 Lite is based on the NEO’s. To be as light as possible, the non-PRO O4 has no microSD slot; you can only record to the onboard 26GB memory.

The brand-new Racing mode on the DJI O4 Air Unit Series supports up to eight racing drones in the same airspace, maintaining the low 20ms and 15ms latency. Both utilize H.265 video encoding, supporting high-frame-rate transmission at 1080p@100fps, ensuring clear and smooth real-time imagery, regardless of flight speed or environment.

My O4 Air Unit Lite has already been shipped, and after receiving it, I will complete a review and make a more in-depth comparison of these two.

Activation, binding, firmware upgrade, and FCC hack (HAM file mod)

The activation and binding process differed slightly as I received a pre-release test unit. I had to use a provided account and download a modified version of the DJI Assistant 2 (Consumer Drones Series).

To upgrade or downgrade the O4 firmware, connect the Type-C cable. However, for activation, you must also connect the drone battery. My O4 came with the latest firmware, but on the Goggles 3, I needed to downgrade the firmware to the previous version to support the O4.

To pair the G3 with the O4 AU, first push and hold the headset’s power button until it beeps (pairing mode), and then press the tiny bind button on the O4 (under the micro SD logo) until the red LED starts flashing. If the goggles 3 is in a different “aircraft” mode, it will prompt you to switch to O4 mode.

Next, I copied the “ham_cfg_support” file onto the Goggles 3 micro SD card. This way, after reboot, FCC mode with up to 1200mW transmission power and all VTX channels will be enabled, resulting in a much more stable and longer range.

Update: A week before the official launch, I received another email from DJI about the new firmware for the O4/O4 Pro (v01.00.00.13), recommending installing it before continuing testing.

DJI O4 Air Unit Pro: Performance and image quality

The range of an FPV drone depends on battery life, radio control signal strength, and video feed quality. To test the performance of the O4 Air Unit Pro, I used my long-range Volador VD6 with ELRS GEMINI RX and a RadioMaster Zorro transmitter with 2x1W GEMINI TX. Previously, the drone was equipped with an O3, so I had a basis for comparing the performances of the two air units.

Not being used to the O4’s limits, I didn’t dare to fly very long distances from the beginning. The first orange and even red alarm signals appeared on the goggles when I exceeded 1 km. Both of my Goggles (3 and O4) had stock antennas and default bitrate, channel, and power settings. In the future, I will try different settings to see how far I can fly.

The DJI O4 Pro captures sharp, vibrant footage with excellent dynamic range and accurate color reproduction. Even in challenging lighting conditions, it maintains impressive clarity and detail.

As the sun’s altitude drops in winter, there are many reflections on the lens, but this is somewhat normal. Using a quality ND filter might improve the image, and during summer, when the sun is above the drone, this phenomenon should not occur.

Recording at 4K@120fps gives you four times slow motion for a more cinematic look. D-Log mode is also a powerful tool for content creators aiming to capture high-quality, professional-grade footage. It is a unique color profile developed by DJI to capture a wider dynamic range and preserve more detail in an image’s highlights and shadows.

The DJI O4 Pro features Rocksteady 3.0, which was introduced with the Osmo Actio 4 camera. This Electronic Image Stabilization (EIS) technology is realized by increasing the shutter speed, analyzing the images captured by the CMOS sensor, and compensating by cutting off the edges. You will lose a slight field of view when enabled, but the footage will be much smoother. The O4 AU Pro also features Gyroflow stabilization if you prefer post-processing.

Do I still need a GoPro?

Personally, I’m happy with the quality of the O4 Pro, and I will probably skip using an additional action camera for 4K recording. Of course, this is only possible on FPV drones with clean views without props and other parts in the video.

Instead of the extra weight of a GoPro, you can use higher-capacity batteries, giving you extra flight time for more enjoyment.

DJI O4 Pro vs DJI O3 Air Unit

The DJI O4 Pro is ideal for pilots seeking the latest technology, better video quality, extended range, and enhanced performance. At the same time, the DJI O3 Air Unit remains a reliable and cost-effective option for those with established systems or looking for excellent performance without the premium price. Luckily, switching from one platform to another can be done quickly without complicated modifications of your FPV drone or advanced configurations.

For me, the most significant upgrade from the O3 and Goggles V2 combo to the O4 Pro and Goggles 3 is the ability to capture FPV footage with OSD (flight parameters). Like its predecessor, the O4 Air Unit series is fully compatible with BetaFlight OSD (CANVAS).

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Since 2014, FirstQuadcopter has reviewed, thoroughly tested, and rated hundreds of products, including drones, gimbals, power stations, action cameras, 3D printers, video lights, and other high-tech gear to help you make better buying decisions.

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