O4 Air Unit Pro vs O3 Air Unit – Upgrade or Stay

In my O4 Air Unit Pro review, I already provided a summary comparison between these two DJI digital FPV systems. To make things clearer and help decide if the upgrade is worth it, I put together this more detailed article.

The O3 Air Unit was released on August 9, 2023, and the O4 Air Unit series on January 9, 2025. Certainly, in these 16 months, DJI has worked to bring many improvements to its own digital HD transmission system, and to the joy of hobbyists, they have managed to achieve this without increasing the price. Both aerial units were launched on the market at a price of $229. Of course, with the release of the new Air unit, the price of the older one dropped to $179.

Performance-wise, the O4 Air Unit Pro promises a range of up to 15 km with a latency of 15 ms, while the O3 Air Unit offers a range of 10 km with a latency of 28 ms. The new O4 also has a bigger image sensor that improves low-light performance. The O4 Pro has a 1/1.3″ CMOS sensor and the O3 a 1/1.7″ one.

In terms of design, these two DJI Air Units look similar. The O4 Pro VTX measures 33.5 x 33.5 x 13mm and weighs 31 grams. The O3 VTX measures 25 x 30.5 x 14.5 mm and weighs 39 grams. While the third AU has one antenna, the fourth AU has two antennas. Both digital VTXs features 20×20 mm and 25.5×25.5 mm mounting patterns.

O4 Air Unit Pro vs O3 Air Unit comparison table

I’ve compared the key specs of both Air Units in the table below, and as you can see, the new O4 AU Pro outperforms the O3 in every aspect, from weight and range to camera performance. The only thing that stands out for the older O3 is the lower price and compatibility with the Goggles V2.

Challenges when considering upgrading from O3 to O4 Pro

Wiring the O4 Air Unit to the flight controller is easy; it uses the same 3-in-1 cable and pinout as its predecessors. You just need to unplug the O3 and plug in the O4

While both AU VTX have the same mounting points and about the same dimensions, the O4 Air Unit Pro camera is slightly bigger due to the larger image sensor, so it will require a newer mount or even frame modifications. As the O4 has two antennas and the O3 only one, you will need also to replace the TPU antenna mount. If the VTX antennas are above the GPS module, you may have problems, as the shielding will be greater in the case of the O4.

My biggest problem, and most costly, when upgrading from the O3 Air Unit to the O4 Pro Air Unit, was a compatibility issue with my existing FPV goggles. As the Goggles V2 is not compatible with the O4 Air Unit series, I needed to upgrade to the newer Goggles 3.

O4 Air Unit Pro vs O3 Air Unit: Compatibly with existing FPV gears

The O3 Unit is compatible with pretty much eventing from DJI’s FPV ecosystem. It can be used with the DJI FPV Remote Controller 2 and 3, as well with all DJI FPV Goggles, including the older V2. On the other hand, the O4 Air Unit series, is compatible with FPV headsets that support Ocusync 4.0 technology. Both digital systems can be used with ELRS, TBS Crossfire, FrSky or other external radio receivers and are compatible with BetaFlight OSD (CANVAS).

DJI FPV system compatibility table

Conclusions

During my tests, I noticed that the O4 Air Unit Pro has a better range than the O3, but the O4 doesn’t penetrate obstacles any better than the O3. Obstacle penetration is about one thing, as you’ve discovered: Power, and the O4 is the same transmit power as O3. Instead, signal coverage is also better on the O4 Air Unit Pro due to the dual-antenna system.

In my opinion, if you already have an FPV drone with the older O3 Air Unit, you should stick with it. On the other hand, if you plan to build a new drone, you should definitely use the newer O4 Air Unit Pro. For the extra 50 bucks, it provides better range, lower latency, higher frame rate, and many more benefits.