The GT-R90 is a micro racing drone from Diatone that uses 2″ propellers and supports 3S and 4S LiPo batteries. In this review we will check out its features and performance.

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Your can purchase the GT-R90 at Banggood.com and Diatone.HK

Parts List and Features

This tiny 2-inch micro quadcopter is packed with latest hardware and technology, which can only be found on larger 5″ racing quads normally. It’s pretty amazing how they managed to fit so much stuff in this little package.

Hardware:

• Fury F4M Flight Controller (FY4O target) – running the latest Betaflight 3.2.1 firmware and Dynamic Filter
• TBS Unify Pro HV VTX – with linear dipole antenna
• F15HV 4in1 ESC (BLHeli_S allowing DShot600)
• Sunnysky Edge Racing 1104 6000KV
• 2030 triblade propellers

It doesn’t come with RX and battery.

Features:

• Supports 3S and 4S LiPo batteries (400mAh – 650mAh)
• Smart Audio for VTX Control
• Betaflight OSD
• Current Sensor
• Blackbox Log Recording (16MB flash memory)

What? 4S on a 2″? LOL – Sub-100mm micro quads normally use 2S Lipo batteries, maybe 3S at most. But the GT-R90 supports up to 4S!

Another great thing about the GT-R90 is the TBS Unify Pro VTX that comes pre-installed. The Unify Pro is one of the best quality VTX’s we have been recommending on our VTX shopping list for months.

Not only it has very clean signal, it also has “SmartAudio” feature which allows you to control your VTX’s settings remotely, from Betaflight OSD and your Taranis TX.

Closer Look at the GT-R90 Micro Quad

The GT-R90 uses a 95mm uni-body frame, with a wide, low profile design. The arms are 3mm thick carbon fibre, the build is very sturdy and there is no noticeable flex in the arms.

The quad weighs at:

• 71g without prop guard, RX and battery
• 78g with prop guard, but without RX and battery

It’s using an “unknown” micro CCD camera, and the video quality and WDR are actually pretty decent – check out our test footage later in this article to see how the camera performs.

The Diatone GT-R90 doesn’t come with a radio receiver and you need to install your own.

There is a 3-pin JST cable soldered to the FC already for your RX, but it’s useless for me because it’s not compatible with any of the Frsky RX.

The FC is soft-mounted on top of the 4-in-1 ESC.

The VTX sits inside a plastic case under the ESC’s, and the dipole antenna is protected by a plastic tube.

However I don’t like the antenna pointing down to the ground. Perhaps this can minimize the chance of damaging the antenna in crashes and by prop strikes, but this is bad for video signal. You can lose video signal when the quad is flying away from your, because the signal is the weakest when the antenna points directly at your video receiver.

I wish the antenna can point up slightly instead of pointing down, so that when you fly forward the antenna would be closer to being vertical and signal will be more consistent and reliable.

It’s rare to see a current sensor in these tiny builds due to the lack of space on the flight controller. Diatone integrated the current sensor in the XT30 connector and I must say this is a very clever idea!

To learn about the benefits are doing this, check out my articles “current sensor in battery connector“.

It’s using Sunnysky Edge Racing R1104 6000KV motors. Beware that the motor screws don’t have loctite on them, and I strongly recommend putting loctite on your motor screws, especially if you plan to use 4S on this quad it can be quite powerful :)

The removable prop guards are made of the exact same material as the propellers. But you will need shorter screws (2mm shorter) if you decide to use the quad without prop guards, otherwise the original screws can touch the motor winding.

The motor wires are secured by these little plastic holders, a better looking solution than using electrical tape :)

Battery strap is too short for my batteries (4S 650mAh), and normal straps (20mm width) that we use on bigger quads don’t fit through the slot. So in the end I had to use a rubber band and some velcro to hold the LiPo in place and that seems to work well.

It also comes with molded plastic spare parts, including 2 propellers and 2 prop guards. This really reminds me of the model kits I used to play with when I was little :)

Why there is no receiver?

For the build quality of the GT-R90 and the components used, this is meant to be a premium micro quad. But I am a bit disappointed by the lack of radio receiver.

“Cheaper without the RX..” they say

Diatone excluded the receiver so that they could lower the price of the GT-R90, but from the customer’s point of view, this doesn’t really change the total amount we have to spend.

We still have to buy the receiver separately!

And it could have saved us, the users, time and effort to DIY if it was done in the factory. Or maybe give the option of BNF and ARTF kits?

I’d trade the Unify Pro for a cheaper vTX and RX

IMO, you get the most out of VTX Control when using it with Taranis LUA script, so you can change VTX settings from the Taranis.

Yes, you can just do it in Betaflight OSD too, but then you have to be on the right channel on the VRX to use it, so I always find it more efficient and makes more sense to use LUA script.

If Diatone doesn’t want to put the price up, I’d rather see they replace the Unify Pro with a cheaper VTX and a R-XSR receiver that is already installed and configured in the quad, at the factory.

But that’s just me! I am sure there are people who don’t care about this at all:)

Installing R-XSR Receiver

If you are a Frsky user, R-XSR is probably the best choice, XSR might be a bit too big for this quad.

First of all, you need to take the frame cage off to gain access to the flight controller. You can simply remove these four screws on the bottom of the frame.

Then select your preferred RX protocol, PPM or SBUS, by bridging the correct solder pads.

Don’t forget to use the “uninverted Smart Port signal” from the R-XSR receiver, because it’s an F4 flight controller in the GT-R90.

Beware that there are two TX3 pins on the board, I think Diatone specifically designed this FC for VTX’s with Tramp Telemetry or SmartAudio as they put one TX3 pin right next to the Video-Out pin so wires can be arranged in a cleaner manner.

I overlooked this and thought TX3/RX3 on the bottom of the board was unused, and only realized this when neither SmartAudio nor SmartPort was working… Then I moved SmartPort to UART6 and everything was working again.

Finding where to mount the RX and antennas was another challenge, it’s just not as straight-forward as I expected. But I did it in the end, took me about 30 mins to install the RX :)

Setting up

These are the steps I followed to setup my GT-R90.

• Install RX and bind to TX (confirm if RX is working in receiver tab)
• Setup mode for arming
• Basic Betaflight Configuration
  • Set looptime 8K/8K
  • Enable DShot600
  • Set up rates

The Good and Bad

Here is my first flight on a windy day (15 MPH wind).

Flight Performance and Battery Choice

It flies pretty well, even in windy condition. I cannot comment on what battery you should get, because I only have Acehe 4S 650mAh and I don’t have any 3S of this size. But Diatone told me that 3S works just as good as 4S due to the lower battery weight.

The weight definitely plays a big part here.

Despite being on 4S, it felt a bit less agile than the 3″ quad I have, but that’s probably because I am using the same batteries on both of them. I think 650mAh is probably too heavy for the 2″, and 400mAh would be a better choice for either 3S and 4S.

It’s fun flying the the GTR90, I could do the same tricks and moves on a more powerful 5″ quad, so this can be a great training platform for beginners, or for racing in large indoor area.

Propellers – can be better!

The main complaint I have is the propellers, they are too loud and doesn’t sound very efficient. Unfortunately I don’t have any other 2″ propellers to compare. I would definitely recommend getting some other 2″ props to try out if you have this quad.

Current sensor is off

Another minor complaint I have would be the voltage and current sensors. They are are way off and requires calibration, which should have been done in factory IMO.

For voltage (VBAT), you can simply adjust the scale and compare what you get on the OSD, to what you measure on the multimeter. To calibrate a current sensor, it’s a bit more complicated, please check out my guide about current sensor calibration.

Don’t fly (crash) too far away!

Lastly, there is no buzzer.

With the great Unify Pro HV VTX and full range R-XSR receiver, you could easily fly a long way out and forget how far you’ve gone. You have over 1 Km of range easily on this thing… Trying to find a tiny crashed quad in bushes and long grass is a hell of a job without a beeper.

There are buzzer pads on the FC and you can solder a buzzer to them, but it’s not easy to mount it given the tight space.

Perhaps not loud enough, but you can use motor/ESC as lost model beeper :)