RadioMaster Zorro review: blurring the boundaries

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

In this detailed review I'll investigate its suitability for DLG, Electric and sailplane flying. So read on and find out if the Zorro is for you!

In the box

What you get!

My Zorro arrived in a slim package containing:

Transmitter (with internal '4-in-1' MPM)
USB-A to USB-C cable
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 pretty good for an inexpensive unit. All surfaces have a smart semi matt finish. The battery covers have an extra touch of luxury, in the form of a rubberised satin finish.

RadioMaster Zorro

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

Switches and pots

The Zorro is well equipped for such a small unit, with a good selection of switches and pots:

Switches and pots

As a thumber I find the switches a little awkward to operate. This is partly due to their location at the top of the unit, and partly because of their small size and short throw. On the plus side, they are less vulnerable to damage.

The pots have a large angular travel and are better described as 'rollers'. The centre position is marked, however there is no centre detent. That said, I found them perfectly usable for camber control in a DLG.

The top momentary buttons stand proud, and are suitable for DLG launch. The rear momentary buttons are flush with the surface, and could also be used as launch buttons.

Antenna

The antenna is articulated at the base and can be parked safely along the top of the case.

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 set to the maximum and too strong for me. Once adjusted, the gimbals feel very nice. Theyre well placed and I have no trouble reaching the inner corners of their travel.

The supplied stick ends are rather skinny, and I've replaced them with larger non-slip units. The stick shafts have M3 threads.

Each gimbal has a pair of adjusters accessble through the back of the case. The right hand adjuster of each pair is to engage or lock the self-centring spring - clockwise to lock for throttle operation. The left hand screw is for adjusting the friction of the throttle strap.

Mode 1/2 switching adjustments

Ther are two adjusters at the front or each gimbal, for the vertical end stops:

The self centring springs are more difficult to adjust, as you have to open the case first. To adjust the vertical axes it's also necessary to undo the screws for the main board; you then wiggle the board till the adjusters are visible.

See video link at end, which explains the adjustment procedure.

Light and sound

The back-lit LCD screen is generously sized at 55 x 32 mm. Contrast is good, but it's a little slow to refresh leading to a little 'tearing' during transitions. Compared with the panel on the TX12, the Zorro's panel is larger, though with the same 128 x 64 pixel resolution.

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 all three keys look the same. Consequently I often find myself hitting the RTN key by mistake. 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, primarily targeted at drones.
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's are based on the well tested open source design. They emulate a number of different protocols, making the Zorro compatible with a wide range of receivers.

The protocols used in the MPMs are all reverse engineered, however they're well tested by an army of users and the developers are responsive to any issues.

FrSky protocols

If you use FrSky receivers then you'll be pleased to know that both versions have excellent support for the FrSky ACCST (D8, D16 v1/v2.1, LBT/FCC). The nice thing is that the protocol can be set on a per-model basis. This is more flexible than FrSky's own transmitters where changing protocols requires reflashing of the RF module.

Note however that the MPM does not support ACCESS.

MPM frequency tuning

If using CC2500 protocols such as 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 unique ID of another RF module running DSM or ACCST protocols.
The MPM can then transmit using the cloned ID. This means that can swap between the Zorro and a second transmitter running DSM or ACCST without the need to rebind!
This is really useful if you have a large fleet of models which you want to migrate to the Zorro. It also means that one or other transmitter can be used a backup.

MPM with FrSky D16 in 'cloned' mode

Hardware cloning
Using the provided MultiConfig Lua script it's possible to do a hardware clone another MPM. This allows you to swap between transmitters without the need to rebind or capture signatures, regardless of protocol.

To do this, 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, recommended if you pass 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, and won't be considered further in this review.

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.

I would therefore 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. If necessary, calibrate before proceeding.

Operating system

The Zorro can run either OpenTX or EdgeTX. Both systems have the 'low-res' interface, with some menus split into sub-menus. This makes navigation less convenient compared with radios with higher res screens, like the X9D Plus and TX16S.

My Zorro came with EdgeTX 2.6.0 installed. My first task was to import models from my TX16S which runs OpenTX. Unfortunately an attempt using EdgeTX Companion didn't go well due to various issues with ETX 2.6. To work around these issues, I flashed the Zorro with OpenTX 2.3.15, and successfully converted my setups using OpenTX Companion.

Edit: Since writing the review, EdgeTX 2.7 has been released. This version is more stable and converts my Pro templates without issue.

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.

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, replacing the battery cover is not so easy. You have to squeeze the sides and push down firmly, while sliding into place. If you get it wrong, the covers can slide off.

Flight tests

My first tet with the Zorro was with my Pike Precision 2. This is the model I use for F3F competition, and I normally fly this with a TX16S. The Zorro was running my F3F setup and crow aware trim script.

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 better suited, but what the heck, it was fun - and a talking point on the slope!

The second test was with my Topsky DLG. This is where the light weight of the transmitter is of real benefit. To adjust flap camber I used the left hand roller-pot - in spite of early doubts, it's actually quite usable. All in all, the Zorro makes a good DLG radio.

I did however experience more 'RSSI low' warnings than I would expect. Whether this was a failing on my particular unit, or a design compromise I don't know. In the meantime, I wouldn't use my unit in a high flying thermal soarer.

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

The verdict

Despite inevitable 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'.

While it's no substitute for a TX16S for competition sailplanes, it is a viable alternative to the TX12 for sport flying. Compared with the latter, the Zorro is more comfortable to hold, 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
Build quality
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 is 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