The GTB 339 is part of the new Diatone Cube line of products consisting of the GTB 229/239, and GTB 329/339. The difference in numbers represents the propeller size and suggested battery 2S or 3S.
The Cube product line is done by consulting the KababFPV (KababFPV joint design as stated on the Diatone website) and actually he is the on that named this product line. The design is originally by Diatone but Kabab helped them improve the performance and more convenient to own, use and maintain.
Frame and canopy
The frame is cut from Quasi-Isotropic Carbon having the fibers running in four directions instead of just two making it look really skinny but at the same time being very rigid.
It is 4mm thick and 1.6mm wide. The diagonal distance between the motors is 122 mm which gives more than enough space to run 3 inch propellers.
On the top of the stack is the TPU printed canopy which serves also as a camera holder / protector. The canopy is printed in TPU with a decent print quality, but not in a high print resolution.
Motors & Propellers
The motors are MAMBA Racing MB1105 5500KV for the 339 and MB1103 6500KV for the 2S GTB 329 version. These are stronger and more robust than the 1103s and in the short time that I have tested the GTB 339 they seem to perform extremely well providing up to 5 minutes of flight time on 450 mAh battery, even when not minding the throttle.
The GTB 339 comes with one set of HQ 3×2 propellers. A bit disappointing that Diatone has included only one set of such propellers and at the same time provides two battery straps. I wonder if the propellers will outlast the battery strap or it will be the other way around 😉
The propellers bend easy in crashes but they could be easily straightened out with no impact to the flight performance.
At the time I’m writing this article Gemfan has announced their new version of 3 inch low load propellers with 1.8 pitch, intended light builds with high KV motors and I think that they will be perfect for the GTB 339 since it is a bit on the higher side with the KV of the motors.
The Diatone GTB 339 is build upon the Mamba F411 16×16 stack consisting of 4in1 BlHeli_S speed controllers and MAMBA F411 NANO F4 flight controller preflashed with Betaflight 3.5.7.
The ESCs support 2-4S voltage with continuous current of 13 amps and burst of 15 amps for about 10 seconds.
Here is a thorough review of the Mamba 411 flight stack done by Albert Kim:
Video transmitter and fpv camera
The vTx is positioned on the top of the Mamba 411 stack and it is TBS Unify Pro32 Nano.
It comes locked on 25mW but it can output up to 400 mW when unlocked.
Since the TBS Unify Pro32 Nano has no mounting holes it is soldered on an adapter board with 16 x 16 mounting holes.
In order to save weight Diatone opted out to use a regular dipole antenna for the vTx which in my experience works decent on 25 mW, but if you plan to fly with this antenna I would suggest you to unlock the Unify vTx and use it on 100 mW.
The unlocking procedure is done by powering the vtx, switching it to a band menu by holding the button for 3 seconds (the red led will blink once for channel menu and two times to signalise that you are in the band menu). After entering the band menu, press and hold the button for 30 seconds. The vtx will lit up both blue and red leds after reboot to signalise that it is unlocked.
Camera is the RunCam Nano V2 with 2.1mm lens. It is a budget camera but it provides a pretty good image.
Since I usually go flying at the end of the day, I was able to test the camera in lower lighting conditions and I can say that it performs decent in comparison to the Foxeer Micro Predator V4 which I fly on mu bigger quadcopters.
The Diatone GTB 339 comes without the front standoff so the usb port is accessible and you could plug it in order to configure the flight controller. Once you are finished it is advisable to put the standoff in its place in order to secure the canopy and get jellofree fpv video.
The overall weight with the RXSR receiver and the propellers with bolts is around 66.5 grams and the all up weight with a 450 mAh battery is around 104 grams.
PNP means no receiver
There is no receiver included in the package, since this quadcopter is only sold as PNP.
By default it comes with a wire harness soldered on the flight controller and additional connector that will help you connect RXSR receiver without additional soldering and get you in the air in a very short time.
There are two small tube shaped holes on each side of the camera that should be used to route the antennas. If you have a spare antenna tubes you could insert them on each side of the canopy and have a neatly routed antennas like in the photo below. If you leave them unprotected take care that the antenna length is short enough so they will not get chopped by the propellers in a crash.
A word of caution. If you are inexperienced pilot then I would warmly suggest you to buy the GTB 229 or 239 in order to have less steep learning curve. The GTB 339 is intended for more experienced pilots that will be able to handle its power.
The flight experience is similar to flying a 5” quadcopter minus the weight with doubled flight time.
Similar to a 5” the GTB 339 requires a bigger flying area in order for you to see its full potential.
Here is a DVR recording from my first flights on two different locations. The first half of the video is recorded in a wider flying area and the second one in a small park.
The flight performance is excellent. The GTB 339 motors have tons of power which combined with its weight provide rocket like performance. This on the other hand requires you to adjust to the throttle response, but after a few lipos you will barely notice that and enjoy the performance.
If by any chance you are having a hard time adjusting to the throttle response, I would suggest lowering the Betaflight throttle boost setting to 3, which will give you a bit more nimble throttle response.
Diatone suggests using 3S 300mah battery and the GTB 339 comes tuned for that lipo size, but I have been flying it with 450 mAh after I have slightly adjusted the PIDs.
Just a side note, I have also tried flying it with the default Betaflight PIDs and it flew better than on the factory PIDs on a 450 mAh 3S battery. So if you are having problems with your tune and you aren’t into tuning, I would suggest you just switch to the Betaflight default tune, which is not perfect but is just performs better on heavier batteries.
If you need help tuning your GTB339 to fly with heavier batteries, let me know in the comments below, I would be glad to help.
I have several crashes in the field with relatively soft landings on grass that didn’t do any damage. The most serious one was hitting a concrete pole but I got away with only one bent propeller and small scuff on the camera lens casing.
This little thing flew so good even with the bent propeller that if it wasn’t for different sounding propeller noise I would not have noticed anything.
Pros & Cons
- Excellent build quality
- Great flight performance
Long flight time
- Strong carbon fiber frame resistant to moderate impacts
- Provides experience like flying a 5 inch quadcopter but it has cheaper maintenance costs.
- It is bigger and heavier than the other cube models and it can hit harder thus doing more damage.
- It the esc burns you will have a hard time replacing it since there is no normal connector between the FC and ESC, just a regular 6 or 7 wires which require really good soldering skills. Or you will have to buy the ESC and FC together so you could replace them without soldering the tiny wires.
- The battery strap could be replaced with rubber bands in order to save weight.
This is one of the best micro quadcopters that I have the chance to review, from build quality to flight performance. An excellent park flyer for those winter days when the day is short and you don’t have enough time to go and fly on a remote locations.
If you are an experienced pilot looking for a toothpick style quadcopter, as a new addition to your fleet, this should be on your consideration list.
Interested in buying it? Get the GTB 339 from BangGood for a $115 by using the BGMINIMICRO coupon code. The coupon is valid for 30 purchases or till 11.30.2019