Friday, 11 December 2020

RadioMaster TX12 - mini marvel or... ?

Looking for a compact and inexpensive radio which runs OpenTX? Well here's something which might might be of interest - it's the new TX12 from Radiomaster, and it's possibly the smallest and cheapest OpenTX transmitter on the market.

I've been playing - and flying - with a pre-production unit for the last couple of weeks. Read on and find out if this little baby is for you...



Full disclosure - Radiomaster kindly sent me a pre-production unit to evaluate. RM did not seek or receive access to this review prior to publication. 


Baby steps

Remove the TX12 from the simple packaging, and the first thing that strikes you is its size - this transmitter is small! Here it is, next to the FrSky X9D:



Dig in the box and you'll find some accessories:

  • A USB-C cable for charging and data transfer
  • An antenna (yes, it's removable)
  • A plastic plug for the antenna exit
  • An instruction leaflet (very bare, but this was a pre-production unit)


Ergonomics

The shape of the TX12 is all curves and smooth surfaces, and once I got used to the size, I found it comfortable to hold. Yes, the grips could be a little deeper and the sides could be textured, but the designers have struck a decent compromise given the low price.




There are some nice touches, like the folding handle:



The trainer and USB ports are in the right place, at the top of the unit:



Fit and finish are adequate, if not quite up to the standard of the TX16S.

Switches, buttons and sliders

The TX12 sports four switches, two sliders, and two momentary buttons. All are symmetrically distributed, so you won't be complaining that a switch is on the 'wrong' side.

Switches

First surprise: there are no 2-position switches and no momentary switch - all the switches are 3-position types. If you need a 2-position switch, it should be easy enough to replace one of others (you can update the switch type in the Radio Hardware menu). Alternatively, you may be able to use one of the momentary buttons.

The quality of the switches seems fine. However the switches at the front are, rather annoyingly, mounted at an angle  - when in the middle position they're actually pointing upwards slightly.

Momentary buttons

The two momentary buttons (labeled A and D) are an unusual feature. 

The buttons are electrically identical to regular momentary switches - the only difference is you have to take your thumb off the stick to operate them. That said, they're fine for the majority of tasks like DLG launch presets, motor arming, RSSI callouts and so on.  And with a little creative programming, they can do things like push-on, push-off (I'm using this technique to emulate a dual-rate switch). 



Sliders

The sliders are most welcome at this price point. However they feel imprecise and the centre detents are vague. I've since printed my own levers with a non-slip finger pad, and the feel is much improved though of course precision is unchanged.

The photo below shows the lever as supplied:

And this is my printed version:



Power switch

The power switch incorporates a bright 3-colour LED.  Blue for booting, red for blocked/charging, and green for transmitting. 

Delays for startup and shutdown can be configured in the Radio Settings menu. If you're really impatient, you can also disable the splash screen. 

Antenna

The antenna is removable. A warning sticker reminds you to attach the antenna before powering up the transmitter with the internal module active - otherwise you risk frying the module. I'm keeping my antenna permanently attached!

One nice thing is that the antenna is slightly shorter than average, making it less vulnerable to damage. 

Gimbals

As expected at this level, the gimbals are all plastic and use conventional pots rather than Hall sensors. The soldered joints are well supported and there's minimal flexing of the cables.

It's nice to see that the shafts are ball raced.


Stick length and spring tension are adjustable. The tension out of the box was far too strong for me, and I ended up reducing it to the minimum. It's well worth spending a few minutes to get it right. Once properly adjusted, I found the sticks nice to use.

The throttle axis has a friction strap. I had to tighten mine down to achieve sufficient friction. It would be nice to have a ratchet as well, but - as the photo shows - there's insufficient room for two straps.



[Edit Jan 2021: the throttle pot on my unit has developed a problem. A perfect excuse to check out the RadioMaster support ticket system - I sent a vid and description, and received a response within 24 hours - and the promise of a new gimbal.]

Screen 

The screen is a backlit 128 x 64 monochrome panel, similar to those used on the Q X7, X9 Lite etc. The backlight is only needed in dim light, and is configurable in the radio settings menu. 

Sound

The sound from the single speaker is loud and clear - top marks here!

Firmware

My TX12 came with a development build of OpenTX 2.3. No microSD card was provided. The transmitter worked out of the box, however functionality is limited without the card. So the first thing I did was dig out a spare card, and populate with the requisite files from the Radiomaster website.

I also downloaded the latest nightly build of the Companion 2.3.11 from the OpenTX site. Unfortunately the sim for the TX12 is not yet supported, but that will no doubt be corrected for the final firmware.

Programming controls

The programming controls follow the example on the TX16S, with six buttons and a knurled metal scroll wheel. All have a nice positive action. However, I do feel that having six buttons for navigation is overkill as illustrated by the FrSky X9 Lite which has just three buttons and a scroll wheel, yet is both simpler and easier to navigate.


The TX12 incorporates the small-screen variant of OpenTX, with some menus split into sub-menus. Programming can be a little fiddly (you'll probably want to use Companion for larger projects), however the functionality is the same as any other OpenTX radio.

Internals

The case is held together by six screws in the back, and two clips at the top. Before removing the back, it's important to release the battery cover first as it can bend and snap (no, it didn't happen, but it could).


The back comes off to reveal a single large printed circuit board, with neatly arranged wiring. The RF module is soldered directly to the board. 

Having everything on the main board is great for reliability. The only downside is that if a subsystem fails, it may mean replacing the whole board.


The switch wires are soldered without the usual heatshrink tube. I have no problem with this - on the contrary, it makes it easier to replace a switch. 

RF and protocols

The internal multi-protocol module contains a single RF chip, the CC2250. This supports Graupner HOTT, FrSky D8/D16, Hitec, Futaba S-FHSS and just a few other protocols. Spektrum protocols are not supported.

One benefit of using a single chip module is a 1db increase in power compared with the same chip in the 4-in-1 module. This equates to around 12% extra range.

For FrSky users, the MPM supports cloning of another transmitter running D8 or D16 (v1 or v2, LBT or FCC). 

The designers have somehow found room for a JR-style external module bay, thus  extending the protocol options to Crossfire, Spektrum, M-LINK etc. If using an external module permanently, it makes sense to remove the main antenna (remembering to disable the internal RF to avoid damage).

Battery

The battery arrangements on the TX12 are simple and flexible. Two 18650 batteries fit into a tray which slides in from the bottom. At first it seems an impossible fit, but it all works beautifully. The tray plugs into the main board via a 3-pin balance connector, so it can be removed for external charging if required.


Remove the tray and there's room for an even larger pack.


Charging 

The built-in charger is a great feature at this price point. Simply connect to a USB source using the included cable - the status LED goes red to indicate charging, and goes off when it's complete. Done! 

The USB-C port is also used for data transfer with the Companion software, and for controlling a sim.

Flight tests

For the flight tests, I used my Mini Ellipse, a 1.5 meter sloper which I've modified for six servos and crow brakes. To control the model, I used my F3F setup and crow aware trim script. This is a complex setup with 55 mixers - it's impressive to see it all running on such a compact unit! 

The receiver is a FrSky G-RX6 with ACCST 2.1 firmware. 

As for the flying.... it took a couple of flights to familiarise after which I felt perfectly at home. There were no RSSI warnings or glitches - it all felt 100% solid. 

I also flew my Ahi., using a simpler template. For this model, I configured one of the buttons as a 2-state toggle for high/low rates. 

[Edit: I've since had two more sessions with the TX12, and the more I fly with it, the more I marvel at this little powerhouse. A tip: if using a neck strap, use thin straps to avoid obscuring the screen.]

Conclusions

Despite its small size, the TX12 is a versatile and fully capable OpenTX transmitter. The inclusion of USB charging makes it especially attractive. Above all, this transmitter is fun to use.

There are just a couple of niggles. The sliders, though welcome at this price point, are rather feeble. Also the momentary buttons, while useful in their own right, can't make up for the lack of a proper 2-position switch (though you could fit your own). Finally, the usual caveats about OpenTX apply - I love it, but some find it tricky to program so do remember to do your research first.

Overall, the TX12 is a fine choice for simpler gliders, DLG's, foamies, simple e-flight models, controlling a sim, flying a quad... or just learning about OpenTX. And, at just £55, it's a steal. If Radiomaster took mine back, I'd have no hesitation in buying another one. And there's no higher praise than that!

Specifications

  • Size: 170*159*108mm
  • Weight: 363g
  • RF Chip: Single-chip Multi-protocol(CC2500)
  • Supported Protocols: Corona, Hitec, Futaba S-FHSS, Frsky D16/D8, RadioLink, Graupner HoTT
  • Transmitting Power: 20dbm (100mW)
  • Antenna Gain: 2db
  • Working Current: 160mA@8.4V
  • Voltage Range:6.6-8.4v DC
  • Range: > 2km @ 20dbm (depending on receiver)
  • Radio Firmware: OpenTX(Transmitter)/  Multi-Module(RF module)
  • Channels: Up to 16 (depending on receiver)
  • Display:128*64 Monochrome LCD display
  • External module: JR/FrSKY/Crossfire compatible
  • Upgrade Method: USB/SD card* & OpenTX Companion PC software.

2 comments:

MattyB said...

If you can get one of these from BG at the moment you are doing very well - my two order attempts have both been cancelled for "logistical reasons" despite other parts of the orders coming through. Banggood couldn't tell me what they were though; bloody Covid/Brexit!

MattyB said...

Update - apparently these should be available in the UK from mid Jan 2021, Brexit delays permitting... https://www.hobbyrc.co.uk/radio-transmitters