We recently did a roundup of all the popular 3-inch FPV drones with the DJI O4 system and concluded that the DeepSpace Seeker3 stands out as one of the best options based on specs and design. As promised, I picked one up for a more in-depth review to determine whether this is an FPV drone truly worth getting!
Check out my 3-inch FPV drone with O4 Air Unit comparison here: https://oscarliang.com/best-3inch-micro-fpv-drone/
Where to Buy
Get the Seeker3 here:
In the box:
- 1 × Seeker3 3-Inch 4S Freestyle FPV Drone
- 2 × Battery Straps
- 8 × HQ T3×3×3 Propellers (2 sets)
- Mounting hardware for DJI O3/O4 Pro Air Unit
- Manual
- 2 stickers
Specifications
- Frame wheelbase: 139 mm
- FC: HAKRC F722 (ICM42688-P Gyro, 16MB Blackbox)
- ESC: 40A 4-in-1 BLHeli_32
- Motors: Aether 1505 4000KV
- Propellers: HQ T3×3×3
- Compatible FPV Systems: Analog / DJI O4 Pro / DJI O3
- Receiver Options: ELRS 2.4 GHz / TBS Crossfire / DJI Remote Controller (with O4 or O3)
- Battery Connector: XT30
- Recommended Battery: 4S 650–850mAh
- Max Battery Bay: 72 × 26 × 33 mm
- Weight (without battery): 178g (including DJI O4 Pro Air Unit)
The 1505 motor size has become the new standard for today’s 3-inch and 3.5-inch quads. In the past, we often used 1404 motors, but they always felt a bit underpowered compared to 1505s. The Aether 1505 motors deliver excellent torque, giving the Seeker3 a power-to-weight ratio that feels much closer to a lightweight 5-inch freestyle quad.
Installing the DJI O4 Pro Air Unit
The version I received did not come with the DJI O4 Pro, so I had to install it myself — but the process is straightforward. Here’s a quick overview.
You can leave the SBUS wire connected. It’s wired to UART3 (RX3) on the FC, which isn’t used by default, so it shouldn’t cause any problems. However, if you plan to use UART3 for another peripheral, make sure to remove the SBUS wire from the harness.
The O4 Pro Air Unit connects to UART4, and it’s already configured in Betaflight. You shouldn’t need to change any settings — it should work right away after installation.
Design and Build
The DeepSpace Seeker3 has an old-school design, but it’s practical and easy to maintain. It uses a deadcat style frame, which helps keep the propellers out of the camera view.
The carbon fiber frame consists of:
- Replaceable 3.5mm thick arms (about 7.5mm wide)
- 2mm thick top plate
- Split 2mm thick bottom plates
- Arm guards, the GPS mount, and antenna mounts are all 3D printed from TPU.
At the front, there’s a CNC-machined aluminum camera mount designed to fit DJI O3, DJI O4, and even analog cameras. This mount isn’t just functional; it adds rigidity to the front end and gives the drone a premium, high-quality look.
The XT30 connector is securely mounted at the rear, preventing the power lead from flopping into the props. However, I would have liked to see a bit more solder on the joints for extra reliability. It would also be wise if DeepSpace had applied liquid electrical tape or glue over the joints to prevent potential short circuits.
The ESC comes preloaded with an older BLHeli_32 firmware version (32.8). During my testing it seems to work fine and didn’t cause any issues, but note that BLHeli_32 development has officially ended, meaning future updates are no longer possible. More details here: https://oscarliang.com/end-of-blheli_32/
Minor Issues:
- The receiver only powers up when a battery is connected, not through the USB port. This makes bench setup and troubleshooting less convenient, as you’ll need to either remove the propellers or use a smoke stopper for safety when working on the drone on the bench.
- The current sensor isn’t properly calibrated — it overestimates current draw considerably. Setting the amperage meter scale to 275 seems to fix the readings.
GPS Module and Rescue Mode
GPS Rescue Mode is a fantastic feature — it’s essentially a return-to-home function that brings your drone back to its takeoff point when you lose signal. It’s especially valuable for beginners and long-range pilots who want peace of mind in case of a failsafe or loss of orientation.
The Seeker3 ships with a GPS module pre-installed at the front, which is an ideal location since it’s far from both the VTX and RC antennas, reducing interference. As a nice design refinement I wish the GPS mount had about a slight upward tilt so it stays relatively level with the ground during forward flight.
DeepSpace didn’t specify the exact GPS model used, but based on the number of satellites detected (up to around 25), it’s almost certainly M10-based — which is excellent. That said, the module is quite tiny with a small antenna, so it can take around 2 minutes to lock onto at least 8 satellites on a cold start. Once powered up, though, subsequent satellite search are much faster.
GPS Rescue is pre-configured as the default failsafe action out of the box, but it’s not assigned to a switch in the Modes tab, so you’ll need to set that up manually. In my testing, it worked well in open fields. However, a few parameters can be optimized, such as:
- Throttle Hover – should be tuned to match the battery and overall weight of your setup.
- Return Speed – can be increased considerably.
- Channel Fallback Settings – not configured.
You should always fine-tune Rescue Mode for your unique flying environment to ensure it performs reliably. Check out my full tutorial here: https://oscarliang.com/setup-gps-rescue-mode-betaflight/
One minor inconvenience — the USB connection doesn’t power the GPS module. You need to plug in a LiPo battery to power it, which also turns on the air unit/VTX. This can introduce interference and slow down satellite acquisition during startup.
Flight Performance
Right off the bat — the Seeker3 rips. Despite its small size, it doesn’t feel underpowered at all. Acceleration is instant, and throttle response feels crisp.
In calm conditions, the top speed can reach around 150 km/h, which is impressive for a 3-inch quad. When flown gently, it can also be quite efficient — but those torquey 1505 motors can draw a lot of current at high throttle, significantly shortening flight time. With aggressive freestyle flying, I typically get 4–5 minutes of flight time with 4S 850mAh, but when cruising smoothly, it can stretch to around 7 minutes.
In my test flight video, the wind was around 20mph, and the Seeker3 handled it surprisingly well — though performance can be even better in calmer weather.
It’s almost vibration-free, with only minor instability or propwash during sharp turns or Split-S.
Overall, the Seeker3 feels fast, nimble, and incredibly fun to fly. There are no props in view, making it a great choice for cinematic flying. Compared to a typical 5-inch quad, it’s also noticeably quieter, which makes it perfect for park flying without drawing too much attention.
My Custom PID Tune
The stock PID and filter tune on the Seeker3 is already pretty good — most pilots will be happy flying it straight out of the box.
If I had to be critical, though, the stock tune feels slightly soft and not as snappy or locked-in as I prefer. It’s a conservative tune, which makes sense — it’s more forgiving to bent props or minor vibrations.
That said, there’s definitely room to tighten the tune and push the PIDs and filters a bit further to make it even more responsive and better at handling propwash.
Would you like to see my custom tune for the Seeker3? Let me know — it takes me hours to make a custom tune, if there’s enough interest, I’ll happily do it.
Battery Choice
If you want to stay under the 250g weight limit, the largest battery you can realistically use is the Sub250 4S 720mAh LiHV (get it here: https://oscarliang.com/product-fmf7), which weighs only 67g. Alternatively, the BetaFPV LAVA 4S 650mAh LiPo is another excellent lightweight option.
If weight isn’t a concern, I’d recommend stepping up to the BetaFPV LAVA 4S 850mAh. It offers plenty of punch and longer flight times. The Tattu 4S 850mAh is also a good option, but in my experience, the LAVA has noticeably better longevity — I bought both packs around the same time, yet the Tattu already shows more voltage sag. In my flight footage above, you can actually see low-voltage warnings appearing early during punch-outs when using the Tattu.
When cruising, the Seeker3 draws around 6A to 7A, which is impressively efficient. However, as soon as you start flying aggressively, the current draw increases sharply, so your flight time will depend heavily on your flying style. Expect around 5–7 minutes on a 4S 850mAh LiPo, and up to 15 minutes on a 4S 3000mAh Li-ion pack when cruising gently.
How to Setup
FC / ESC / RX Firmware:
- Flight Controller Board Target: HAKRCF722V2(preloaded with Betaflight 4.4.3). Original CLI Diff available here.
- ESC Firmware: BLHeli32 (Version 32.8)
- Receiver: Generic ESP8285 PA 2.4GHz RX running ExpressLRS v3.5.1
Setup Instructions:
- Bind the ELRS Receiver: Plug in the USB cable, wait about 60 seconds until the receiver enters WiFi mode (green LED flashing rapidly). On your phone, join the ExpressLRS RX WiFi network (make sure to place your phone close to the drone, as the WiFi signal from the FC is extremely weak). Open browser and go to 10.0.0.1, then enter your bind phrase on the webpage. Detailed instructions can be found here: https://oscarliang.com/bind-expresslrs-receivers/#Method-3-Entering-Bind-Phrase-in-Web-UI
- Pair the DJI O4 Pro Air Unit with your Goggles: Follow the instructions here: https://oscarliang.com/how-to-setup-dji-o4-pro/#Pairing-DJI-Goggles-3-with-O4-Air-Unit-Pro.
- Connecting the drone to Betaflight Configurator. Setup the Modes Tab: Configure your arm switch, angle mode, and turtle mode. For guidance, see this tutorial: https://oscarliang.com/betaflight-modes/#How-to-Setup-Arm-Switch
- In Power tab, set Amperage Meter (current sensor) scale to 275 for more accurate current / mah drawn readings.
- Out of the box, you won’t be able to arm until you get a GPS fix. If you don’t want to wait, you could disable “Allow arming without fix” in Failsafe tab – but note that rescue mode won’t work when there’s no GPS fix before take off! Or change failsafe method from Rescue to Drop (this essentially disable Rescue mode when you failsafe)
- To setup OSD for the O4 properly, make sure to re-select HD in OSD video format (select analog then select HD and save, for some reason the canvas was stuck in analog although HD was selected)
That’s it—your Seeker3 should now be ready for its maiden flight!
Here’s the included manual:
FC wiring diagram:
Conclusion
The DeepSpace Seeker3 isn’t cheap — but you get what you pay for. If your budget allows, I can wholeheartedly recommend it.
For freestyle and park flying, the Seeker 3 hits the perfect balance — powerful enough to fly like a 5-inch and light enough to stay under 250g. It’s easily one of the best all-rounder 3-inch FPV drones available right now — especially for those who want a compact quad that can travel, freestyle, and still offer GPS safety.
Get the Seeker3 here:
