The goal of this build is to make a 7″ FPV drone as affordably as possible while still achieving more than 5km range. I managed to source all the components for around $150, delivering performance that surpasses the $215 Darwin129—commonly considered as the “cheapest 7-inch” from DarwinFPV. Sounds promising, right? Let’s dive into the components I used, and I’ll share my experience with building and flying this setup.
If you’re new to FPV, check out my FPV Drone Build Guide, where I cover many tips and tricks about drone building: https://oscarliang.com/how-to-build-fpv-drone/.
If you are new to long range flying, check out my tutorial on the topics: https://oscarliang.com/long-range-fpv-flying-mini-quad/.
Parts List
Here are the affordable hardware I selected for this build:
Total: US$152.77
Note that this price does not include import tax and shipping costs, which can vary by region. You’ll also need a battery, and I’ll offer suggestions on what to get later in this build log.
Flight Time and Range
With this build, I was able to achieve the following flight time, flight distance, and range using a 6S 3600mAh Li-ion battery pack:
In calm weather conditions (~12km/h wind):
- Max Flight Time (landing at 2.8V/cell): 18 minutes 40 seconds
- Max Flight Distance (landing at 2.8V/cell): 16,100 meters
In ~27km/h wind, with a tailwind outbound and headwind inbound:
- Max Flight Time: 14 minutes 30 seconds
- Max Flight Distance: 13,050 meters
- Range: 5km+ easily (I could have pushed further, but I turned back after reaching 5km due to the windy conditions)
Affordable 7″ FPV Drone Kit
This budget 7″ FPV drone kit includes the frame, four 2806.5 motors, a set of propellers, an F405 flight controller, and a 45A 4in1 ESC—all for just $105, which is incredible value!
Get this kit on AliExpress: https://s.click.aliexpress.com/e/_DFAJ26n
This kit offers most of the modern features you’d want in a 7″ long-range build in 2024, at a fraction of the cost. However, there are some drawbacks that might be deal breakers for some users, which I will delve into more details now.
Frame
I really like the design of this frame—it has a long body that can accommodate a large battery on top, with various mounting holes for different FC stacks and VTX. Assembly and building this frame are straightforward despite the lack of instructions.
This 7″ frame weighs around 120g, which is very light for this class. However, the arms are only 5mm thick, and the top and bottom plates are 2.5mm thick. The construction feels a bit flimsy, and it’s not as sturdy or stiff as I would hope for a 7″ FPV drone. A frame that lacks stiffness can contribute to vibrations and tuning issues, which can impact flight performance. But we just want a cheap frame to get us in the air, this will suffice for now.
Flight Controller
The flight controller is the YSIDO F4 V3S Plus FC, and on paper, it has impressive specs.
Firstly, it uses an F405 processor, allowing you to run 4K PID loop frequency and DShot300 with GPS enabled.
It has 3 UARTs, which is enough for my needs:
- UART1 for RX
- UART3 for IRC Tramp
- UART6 for GPS
It includes 5V and 9V BECs, as well as 4.5V pads—these are basically 5V pads that can draw power from the USB port, so you don’t need to plug in the battery when testing the receiver or getting a GPS lock before takeoff. The 9V BEC is great for powering the VTX, which also adds extra filtering.
It even has a barometer (BMP280), which is surprising for a budget FC. The main downside of this board is the MPU6500 gyro, which is noisier and harder to tune than other gyros.
The FC firmware target is OMNIBUSF4SD, and it comes with Betaflight 4.1.1 firmware from 2019, so it definitely needs an update to take advantage of newer features like GPS Rescue.
I planned to tune filters and PID settings, but the SD card for Blackbox logging cracked in a minor crash, and I don’t have a spare on hand. This brings up a potential design flaw in the FC: the SD card slot location – when inserted, the SD card sticks out and is exposed to damage in crashes.
Given the noisy gyro, enabling RPM filter is a must—it flies more stably, and the motors come down cooler. I’m currently using UAVTech’s 7″ preset; the quad still wobbles a bit, but it’s definitely better than the default settings.
ESC
The 45A 4in1 ESCs included aren’t particularly powerful, but they’re more than adequate for this build. A 14AWG XT60 pigtail and a 35V 560uF capacitor are also included.
Unfortunately, the current sensor on this ESC doesn’t seem to work—adjusting the scale doesn’t change anything. I’m not sure if this is a common issue or if I just have a faulty unit. No big deal, I will just monitor battery using voltage.
It comes with BLHeli_S 16.7 firmware (J-H-30). I recommend flashing Bluejay to these ESCs, as it allows you to enable the RPM filter in Betaflight, significantly improving flight performance. I have a guide on how to flash Bluejay: https://oscarliang.com/bluejay-blheli-s/
When I tried flashing Bluejay, I initially couldn’t read one of the ESC in the configurator. However, swapping the ribbon cable (which connects the ESC to the FC) with the spare one fixed the issue—this could have been a bad cable. I flashed the latest version with a 48kHz PWM frequency.
Motors
The included motors are YSIDO V8 S2806.5 1300KV.
There are other kits that offer taller motors i.e. 2807 1300KV. I was tempted to go for those because large quads like 7″ can benefit from larger motor stators, but they are more expensive. After much consideration, I decided against it because the difference would be minimal if I am just cruising—unless you want to do freestyle with it then the 0.5mm taller motors might make sense.
Video Transmitter
When selecting the VTX for this build, my main considerations were:
- Low cost
- High output power (1W or higher)
- Easy mounting in the frame (e.g., 30x30mm or 20x20mm mounting)
- Support for SmartAudio or IRC Tramp for VTX settings adjustment in the OSD menu (VTX Control)
- Wide input voltage support
The cheapest 1.6W VTX I could find was the Ultra1600 for only $22.
Get the Ultra1600 VTX on AliExpress: https://s.click.aliexpress.com/e/_DmxIABp
Although it didn’t quite hit the promised 1.6W in my testing, it’s still worth considering given the low price—note that a brand-name 1.6W VTX would normally cost double or more. If you want a true 1.6W VTX, the iFlight Blitz and Speedybee TX1600 are good alternatives, but these might only give you less than 20% range improvement.
There’s also a VTX from JHEMCU that’s even slightly cheaper, but it has no heatsink, so it might be less reliable: https://s.click.aliexpress.com/e/_DlBNAfZ
VTX Table for the Ultra1600:
# vtxtablevtxtable bands 5vtxtable channels 8vtxtable band 1 BOSCAM_A A CUSTOM 5865 5845 5825 5805 5785 5765 5745 5725vtxtable band 2 BOSCAM_B B CUSTOM 5733 5752 5771 5790 5809 5828 5847 5866vtxtable band 3 BOSCAM_E E CUSTOM 5705 5685 5665 5645 5885 5905 5925 5945vtxtable band 4 FATSHARK F CUSTOM 5740 5760 5780 5800 5820 5840 5860 5880vtxtable band 5 RACEBAND R CUSTOM 5658 5695 5732 5769 5806 5843 5880 5917vtxtable powerlevels 4vtxtable powervalues 25 400 800 1600vtxtable powerlabels 25 400 800 1W6save
FPV Camera
When choosing an FPV camera, look for one with decent specs like a wide FOV, large sensor, switchable aspect ratio (preferably native 4:3), 19x19mm form factor (micro size), low minimum illumination (for better low-light performance), adjustable settings, etc. However, you can’t trust everything you see on the product page—there’s a reason these cameras are so cheap.
This is the camera I picked https://s.click.aliexpress.com/e/_DEijX7N
The image quality is pretty decent, and I think it’s better than the one in the Darwin129 BNF quad.
The main complaint I have is with the fisheye effect—when you do flips and rolls, the image can look slightly distorted. It’s not really a problem though when flying straight. This is something I notice quite often with budget FPV cameras, but it’s not a deal breaker since we’re primarily cruising during long-range flights.
GPS
A GPS module is a must if you plan to fly long-range. With Betaflight Rescue mode, your quad can automatically return to the launch point or by command if you lose signal or orientation.
This is the $4 GPS I’m using: https://s.click.aliexpress.com/e/_DdyGkeH
It’s certainly not as good as more expensive counterparts, but it gets the job done. I’ve used these on a number of my budget builds, and they work as intended. They usually get around 8 to 10 satellites after 3-5 minutes of being powered on, which is the minimum for Rescue mode to function properly. If you can afford a more expensive GPS, definitely go for it! Here are my GPS recommendations: https://oscarliang.com/gps-review/#Recommendations
I’m mounting the GPS on the battery strap, which I found to be a good place for it—it’s well away from the video transmitter and antennas, with no obstructions that could interfere with reception.
Radio Receiver
This is the cheapest ExpressLRS receiver I’ve come across from BAYCK: https://s.click.aliexpress.com/e/_Ddi9WEf
I’m quite happy with its performance, and I’d buy it again. The firmware target is BAYCK 2.4GHz Nano RX, it comes with ELRS version 3.3 firmware.
VTX Antenna
Get a long antenna for the VTX so it doesn’t get blocked by the frame or battery when flying away or turning back.
This is what I bought, and it works well: https://s.click.aliexpress.com/e/_DCnUoJZ
Propellers
A set of propellers is included in the frame kit, so you don’t have to buy them separately, but it’s good to have spares.
The frame kit comes with Gemfan 7040 triblades: https://s.click.aliexpress.com/e/_Dcffy47
These are the 7inch props I’d recommend as an upgrade—HQ DP 7×3.5×3-v1s (Best all-rounder):
Extra Materials
Battery
For long range, definitely consider using a Li-ion battery pack for extended flight times. Most Li-ion battery packs you can buy off the shelf don’t use the best cells, so if you want the best possible performance, consider building your own battery packs using individual cells. Here’s my guide on Li-ion cells recommendations and how-to build one: https://oscarliang.com/best-18650-li-ion-battery/
However, not everyone has the time or skills to make one from scratch. In this case, buying a ready-made battery pack from a well-known brand could be a good option. Actually, I used battery packs from Auline with this 7″ build, and they worked quite well. True, they aren’t very punchy, but for long-range cruising, they are absolutely capable. Here’s my review and testing of the Auline 6S 4000mAh battery: https://oscarliang.com/auline-6s-4000mah-45a/
Unlike LiPo where you are advised to land when voltage reaches 3.5V per cell, you can discharge Li-ion battery much lower, typically down to 3.0V per cell, or even 2.8V per cell. It depends on the specs of your Li-ion cells, check the minimum voltage it can safely handle.
Building Steps
Assembling the Frame
Mounting the Motors
Mount the motors on the arms using the provided screws. I recommend using threadlocker on the screws so they don’t easily become loose over time: https://oscarliang.com/threadlock/
Installing the FC Stack
Before installing the FC and ESC stack, secure the 4 steel bolts in place using 4 M3 steel nuts.
Install the 4-in-1 ESC in the frame, and solder the motor wires to the pads. Solder the capacitor and XT60 pigtail to the ESC.
Install the flight controller, connect it to the ESC using the ribbon cable. Then connect/solder all the components to the FC: GPS, radio receiver, VTX, and FPV camera.
Here’s a wiring diagram for the YSIDO F4 V3S Plus FC.
Here’s another angle showing how I mounted those components in the frame.
Here’s a close-up of the soldering/wiring.
Finishing Off
Install the top plate, and mount the GPS on the LiPo strap—and that’s it. Don’t forget to secure all the wires with zip ties too. The all up weight (without battery) is 473g.
Betaflight Config
I will share my quad’s settings and CLI dump at a later date.
What’s Wrong with Darwin129
DarwinFPV is a well-known manufacturer for low-cost pre-built drones, and they offer a very affordable 7″ BNF drone that provides great value—so why bother building your own? Well, even with the budget parts in this custom build, it outperforms the Darwin129. As I mentioned in my full review of the Darwin129, it has several downsides:
- The Darwin129 only supports a 4S battery, while the higher voltage 6S significantly benefits efficiency and power—crucial for larger long-range builds.
- The Darwin129 doesn’t fly very well and requires additional tuning, which defeats the purpose of “bind and fly.” It has a lot of jello and vibration, which I’m not even sure can be eliminated through tuning—it could be fundamentally hardware-related.
- The included GPS doesn’t work at all, so you’ll have to spend extra on a different GPS, solder it, and configure it.
- In fact, building your own budget 7″ will cost a lot less than buying the Darwin129.
Conclusion
This is the cheapest 7″ FPV Drone I’ve built so far. It offers a sturdy foundation for a highly capable long-range build at an incredible price. The hardware feels modern and feature-packed, offering excellent value for money. With a few carefully selected budget components, this build allows for a low-cost 7″ long-range drone.
