RadioMaster Zorro review: pushing the boundaries

RadioMaster have a new baby transmitter. It's called the Zorro. It's full featured, can run OpenTX and EdgeTX, and is available with a choice of RF modules.

Since it's release, the Zorro has been selling like hotcakes, but that doesn't necessarily mean it's suitable for every application. If you're into sailplanes, DLG's and electric, then read on, and find out if the Zorro is for you!

In the box

What you get!

My Zorro was sent direct from China. In the package were the following:

Transmitter with internal '4-in-1' MPM
USB cable (USB-A to USB-C)
Velcro strap for external battery
Screen protector
A5 leaflet
2 x 18350 batteries
1 meter cable and clip for external battery (also available as an extra)

The last two items are not always supplied with newer sets.

Build quality and general ergonomics

Build quality is generally pretty good, especially considering the Zorro's low price. All surfaces have a smart semi matt finish. The battery covers have a touch of luxury, in the form of a rubberised satin finish.

RadioMaster Zorro

The Zorro feels comfortable to hold, thanks to the good balance and generous 90 mm stick spacing. The neck strap attachment point is perfectly placed.

Switches and pots

The Zorro is well equipped in terms of switches and pots:

Switches and pots

That said, I find the switches a little awkward to operate. This is partly due to their location on top of the unit, and partly because of their small size and short throw. On the plus side, they are less vulnerable to damage from careless handling.

The pots are better described as ‘rollers’. The centre position is marked, however there is no centre detent. Nevertheless, I found them usable for camber control in a DLG. I would be less inclined to use them for motor control.

The top momentary buttons stand proud, and are well suited as DLG launch buttons. The rear momentary buttons are flush with the surface.

Antenna

The antenna is articulated at the base and can be parked safely along the top of the case. It's noticably shorter than normal.

2.4 GHz Antenna

Gimbals

The gimbals have Hall sensors, which is nice to see on a budget radio.

Stick tension out of the box was too strong for me. Once adjusted, the gimbals feel very nice. They're well positioned too - I have no trouble reaching the extremes of travel (I'm a thumber).

The stick shafts have M3 threads. The supplied stick tops are plastic and a bit skinny, and I've since replaced mine with grippier metal tips.

Each gimbal has a pair of adjusters at the back of the case. These apply to the vertical (throttle/elevator) axes only. The right hand adjuster of each pair is for the self-centring spring - clockwise to disengage for throttle operation. The left hand adjuster is for the friction strap (rather misleadingly referred to as 'spring tension' in the graphic below).

Mode 1/2 switching adjustments

There are two adjusters at the front, for setting the vertical stick travel. After adjustment, the sticks should be recalibrated.

Adjusting the tension of the centring springs is - surprisingly - rather more difficult. You have to open the case first, and to adjust the vertical (elevator) tensioner you also have to release the main board. Before attempting this, I would recommend watching the video linked at the end, which explains the procedure.

Light and sound

The monochrome LCD screen is generously sized. Contrast is good, though it's a little slow to refresh leading to some 'tearing' during transitions. Resolution is 128 x 64 pixels.

Sound through the single speaker is clear, with adequate volume.

Size comparison with TX16S

Programming controls

The programming controls follow the usual RadioMaster convention, including their signature double PAGE keys (for forward and back), and a nicely weighted click-roller. All keys have a nice positive action.

If I have one criticism, it's that the RTN key is placed above the two PAGE keys and even after a lot of time I find myself hitting the RTN key instead of PAGE. Also, the legends are recessed, and not so easy to read in poor light.

Programming buttons

RF options

The Zorro is available with a choice of three RF modules:

MPM / CC2500: supports ACCST, HOTT and some others.
MPM / 4-in-1: as above, plus DSM-2, DSMX, SFHSS, M-LINK and others.
ELRS: long range 2.4 GHz protocol.
The back of the unit houses connectors for an external 'nano' style RF module. A common configuration is 4-in1 internal, and ELRS external.

MPM

The MPM emulates a number of standard protocols, making the Zorro compatible with a wide range of receivers. The hardware follows an open source design, and protocols used in the MPMs are all reverse engineered so don't expect any support form the original manufacturer. However the system is well tested by an army of users.

FrSky protocols

If you use FrSky ACCST receivers then you’ll love the MPMs’ capabilities! Both versions of the MPM support D8, D16 v1/v2.1, LBT and FCC.

The nice thing is that the protocol can be set individually for each model. This is far more flexible than FrSky's own transmitters where the protocol is set in the firmware and must be used across all your models.

Note however that the MPM does not support the newer ACCESS protocol.

MPM frequency tuning

If using CC2500 protocols such as FrSky ACCST, the MPM must be tuned to the receiver. It's a two minute job, and can be done indoors.

MPM with Spektrum DSM2 selected

'Capture' cloning of DSM and ACCST
The MPMs offer a 'clone' facility, whereby the MPM can capture the global ID of another RF module running DSM or ACCST protocols. This is done by putting the MPM into a special receive mode.
Once the GUID has been captured, the MPM can transmit using the same ID. This allows you to swap between the Zorro and another DSM or ACCST transmitter, without the need to rebind!

MPM with FrSky D16 in 'cloned' mode

Hardware cloning
Using the provided MultiConfig Lua script it's possible to do a hardware clone of a second MPM. This allows you to swap between two or more MPM-equipped transmitters without the need to rebind or capture signatures, and regardless of protocol. (Note that the second transmitter must have an MPM - hardware cloning is not possible with a non-MPM transmitter.)

To do a hardware clone, you run the MultiConfig script on the transmitter with the source MPM and make a note of two global ids. Then run the script on the second transmitter, copying and saving the global ids to the second MPM.

The MultiConfig script allows you to reset the global ids to their original values. This should be done when passing your transmitter on to a new owner.

Spectrum analyser
The MPM also provides a spectrum analyser function, accessible from the Tools menu of Open/EdgeTX.
ELRS module
The 2.4 GHz ELRS option offers higher range compared with regular 2.4 GHz protocols. However it suffers from reduced resolution, especially on channels 5 and above. It's targeted primarily at drone pilots, so I consider it further here.

Internals

Opening the case involves undoing eight small self tappers, pulling the back off, and carefully disconnecting two cables from the batteries.

Internals

The internal components are quite densely packed, yet everything is neatly organised. The solder joints at the switches and gimbals are well supported.

The RF board is hidden underneath the main board.

Good support for soldered joints

Hardware calibration

On both sets I've used, one of the analog controls only worked over half its travel. Fortunately it was just due to a lack of calibration at the factory. As good practice, I would recommend checking calibration as one of the first tasks with a new set. (Go to the System/Hardware menu, scroll to the bottom and select 'Anas'. Each analog control should span -100/0/100.)

Operating system

The Zorro can run either OpenTX or EdgeTX. Both systems have the low-res version of the interface, where some menus are split into sub-menus. This makes navigation less convenient compared with radios with higher res screens.

My Zorro came with EdgeTX 2.6.0 installed. Unfortunately my first attempt at migrating my models from my TX16S (running OpenTX) didn't go well due to bugs in EdgeTX.

Flashing OpenTX 2.3.15 solved the problem, and this is the operating system which I would recommend if using the 4-in-1 module. (Tip: if the scroll wheel works in reverse, you can correct this in system settings.)

Edit: Since writing the review, EdgeTX 2.7 has been released. This version is more stable, though there are still a few annoying bugs.

Nightly build of OpenTX 2.3.15.
Production version of 2.3.15 is author's choice.

Connectivity

The Zorro is well connected to the outside world, via three groups of ports - see photos below:

TOP FLAP:
Anticlockwise from top left: 3.5 mm headphone jack,
micro SD card, USB-C/data,
DSC trainer

BOTTOM FLAP
External 2S battery port
USB-C charger part

External module bay for Crossfire, ELRS etc.

Batteries and charging

There are two LiIon batteries, one in each grip. In order to keep the Zorro compact, RadioMaster have had to compromise a little - each battery is 18350 size for a nominal capacity of just 900 mAh. Compare this with TX12 and TX16 which take 2 x 18650 cells with a typical capacity of 2500 mAh.

In terms of operating time, I've seen four hours quoted for the MPM versions. The ELRS version draws more current - expect around two hours depending on power output.

Charging is easy - connect to a USB charging source with the supplied cable... wait for the LED indicator to go out... done!

The Zorro takes two 18350 batteries

Extending the operating time

I find the supplied 18350's perfectly sufficient. However, there are ways to extend the operating time.

First, an external 2S 18650 pack can be fitted under the unit, using strips of Velcro (supplied). Connection is via the balancer port at the bottom of the unit. Although it's not ni the manual, reports suggest that the internal batteries do not need to be removed (current is drawn from the source with higher voltage).

Alternatively, you can connect an external battery via a special one-meter cable. The benefit of this method is that there's no limit to the size of battery. One end of the cable connects to the battery via an XT30 connector; the other end plugs into the balancer port. The cable is secured to the transmitter via a plastic clip. My first Zorro was provided with the cable, but it was absent in the second, however it is available as an extra.

The third method is simply to carry a spare pair of 18350's. While it may seem the obvious approach, removing then replacing the battery cover is rather awkward. You have to squeeze the sides and push down firmly, while sliding into place. If you get it wrong, the covers don't align with the body, and can slide off easily. My advice would be to fit the batteries, and leave them!

Flight tests

The first test was a demanding one - to control my number one F3F competition model, a Pike Precision 2 with a FrSky RX6R receiver. The Zorro was running my F3F setup and crow aware trim script.

No problems were experienced. This is pretty awesome - we're talking about functionality on an £80 radio which will out-perform a £1000 plus Jeti. Would I routinely use the Zorro for this? Well no - the TX16S is more comfortable, but what the heck, it was fun - and a talking point on the slope.

The second test was with my Topsky DLG with FrSky GRX-6 receiver with integrated barometer sensor. I'll make it short - the Zorro is an excellent transmitter for DLG, and has replaced my X9D Plus in that role.

During testing I did experience more 'RSSI low' warnings compared with I would expect with, say, the TX12 or TX16S. Whether this was due to sample variation, or a design compromise I don't know - I suspect the former.

Zorro showing crow aware trim script.
Author's Pike Precision 2 in the background.

The verdict

Despite some compromises due to its small size, I really like the Zorro. It has a certain charm. If it were a car, it might be a 'premium mini SUV'.

The Zorro is more comfortable to hold than the TX12, has more controls, and a better screen position. However the TX12 uses larger 18650 batteries. Also, the Zorro accepts nano modules, while the TX12 supports the older and larger JR-style modules.

To sum up:

Pros:

Comfortable in the hand
Excellent support for different RF protocols (4-in-1 version)
Large, high mounted screen
Gimbals
DLG-friendly controls.

Cons:

Switches are a little fiddly
Awkward adjustment of spring tension
Tricky battery covers
Lower range than TX16S (may just be an issue with my unit)

All in all, the Zorro pushes the boundaries of what's possible with a small transmitter. It's a fine choice for pilots who fly a mixture of models, like DLG, drones and slope soarers - and who like to travel light.

RC-SOAR - the Blog

Sunday, 6 February 2022