The radio for my RC project got here today. It's a Hot RC CT-10B, which seems like a bit of a gamble because this company is brand new and not really doing a great job of establishing themselves. The same radios seem to also be sold branded as Meus Racing, although Meus' transmitters are orange.
The listing said it was only going to ship with an 8 channel receiver, but it came with the 10 channel Rx that's supposed to come with this radio. Sadly, it doesn't come with the one I really want (which has 10 channel light control) but their receivers are really cheap, just like their transmitters. F-01AT with gyro and 7-channel LED control is $13.53! The gyro is allegedly not very good, so if you are drifting you should use a dedicated one instead, but it's probably fine for bashers. Or in my case, trail trucks. You also have really incredible control over the lights from the remote, while they default to doing the usual corny stuff you can also program them to run from the controller.
I'm taking a chance on Hot RC instead of the proven DumboRC because I feel this is a market which should be easy to disrupt, so it's plausible that this equipment will work OK. Transmitters and receivers alike are built around completed radio modules, which means more or less anyone can build them. Even if a company chooses to eschew that approach and wants to do all their own circuit boards, the radio chips' datasheets provide reference designs, which can be used to produce working solutions without having to design them from scratch. Compared to a device like a smartphone, which can be had cheaply in most of the world, a R/C radio is a fairly simple device with inexpensive components.
Using the "Program" option I was able to run two steering servos and have them steer at different ratios, which I will need for my 8x8. There's also a dedicated 4-wheel steering mode, and you can also turn off the 4WS modes you're not using, which is pretty great. Unfortunately you cannot map a channel to nothing, so if you are linking a channel as a secondary with a ratio, you will need to map some control to it that you are not using.
"Return voltage" seems to be a feature of all of their receivers with 6 or more channels, which is fairly impressive given the prices. The receivers also all seem to run on 4-9 volts, and I was able to run the F-10A and two servos (with no load) from a 4-pack of NiMH AAs which the Tx says are currently at 5V. The return voltage is 0-27V, and it has a pair of wires, so you could really monitor any voltage on your vehicle that you liked with it. Perhaps in the future they will also support current, but this requires considerably more hardware. You also get signal strength feedback, so you will know if you start to outrange your controller.
All in all I am really impressed with the device so far; it's small and light, doesn't have any corny exposed aerials real or faux, and while the interface isn't great it is generally comprehensible. It even came with a manual which is not totally worthless, for example it explained how the four wheel steering stuff works. There's also a lot of instructional videos online; the videos are kind of terrible, but they are informative. They explain how to do nonintuitive things like using the knobs on the side of the radio to tune the gyro, or how to control the lighting control functions of F-01A and F-01AT (with gyro) receivers from buttons on the Tx.
I do wish there was a smaller lamp control Rx. The F-01A[T] (they are the same on the outside) is 38x25x13mm, which is not much for 10th scale, but is a whole lot for a 24th scale vehicle. And I very much wish the company would be more responsive to English-speaking users, because they are spectacularly unresponsive. The English-language website is also down or never existed, which is aggravating.
The device does support both English and Chinese, and they did a good job on the translation. There are not many words in the interface, but this is still not a given. The manual is well-written as well, if scant. You can also choose from a handful of color schemes, and disable beeps. I don't know if this stops the alarm beeps for the device itself, or for the vehicle battery. You can configure the voltage level of the vehicle battery alarm.
In the reasonably nice box you get the Tx, Rx, voltage wire, a USB Type C to Type C cable (which is used for charging a 18650 battery in the unit; it also will take 4x AA) and the manual, which is just a medium sized folded sheet with English on one side and Chinese on the other, but is in full color. The USB cable is also the trainer cable. Training mode only controls the first two channels, but you can apparently do it across different radios.
I would not actually recommend you buy this radio yet, until I find out if it's going to last. Some of the reviews indicated that it had a pretty short lifespan. They also all say that the battery life is very poor, but this might have been down to a really bad included 18650. When you buy from China, you don't get one of those. I have one that came out of a cheap light in it right now, and it definitely looks like it will eat that up super fast with its bright full-color screen. It also looks like it will take approximately eternity to charge. If you turn it on while it's charging, the voltage meter reads a steady 4.1 volts, which is not a great charging voltage. A lot of 18650s will charge to that voltage or even higher, so by using that as the charging voltage, you are ensuring a very slow charge from 90-100% if it will even get there. It would be wise to carry multiple batteries; I intend to also test it out on Eneloop NiMH AAs soon.
TL;DR: I'm cautiously impressed.
Some time has passed, I'm…
Some time has passed, I'm actually using the radio for the intended purpose, and I have some negative observations. Starting from the bottom up here, in fact the batteries do not ever reach full charging voltage. I seem to have misplaced my cheap-but-functional 1x 18650 wall charger, which does a surprisingly good job. The Tx will never charge a battery past 3.7v. The only other 18650 charger I can find right now, and this is embarrassing, is an eBay-sourced work light... and it will charge them to 3.8v! And keep in mind here that while some of these haven't been charged in a while, they are all cells that should do over 4v. Also, note I said I wanted to test it on AAs, but this model doesn't support that. I don't know if I was looking at an older HotRC or something else entirely when I got this radio, but it will only work with an 18650. No doubt it would be easy enough to mod something else in, just don't forget you're going to need to add a charging port as well. You can get USB to Lithium charger modules very cheap. Do yourself a favor and label the charging port somehow, or get a rubber plug for the original if you're not using the training cable.
Next, the software. At first glance this is fairly impressive especially with the nice bright color screen, and it's only a little irritating that the way you navigate it is through a wide scrolling wheel on top of the unit. But it has some irritating limitations as well. For example trim isn't per-channel, it's per-input. In my case I'm driving two servos from the steering input and I would like to trim them separately, but I can only trim the steering altogether and it affects both channels. In fact, ideally I'd like the option to put expo on channel 3 to adjust for the shorter servo arm which is necessary because the drive shaft is there. (My cheapo servos came with an arm with 3 holes, and I ground off the end position from the second axle servo.) I so far know nothing about what kind of micro is in the Tx, or what kind of display is being used, but I find myself wanting something like Deviation (alternate firmware for Walkera Devo RC transmitters) here. Perhaps if they sell enough of these things it will happen eventually, because this software is quite disappointing and the company is very uncommunicative about when there will be any updates if ever, so it would likely be beneficial. These radios are very inexpensive, so enough people might take a chance on them to create the needed popularity.
Side note on the drive shaft thing. The axle shaft more or less clears my el cheapo servo arm only as long as I have it turned the right way. The axle shaft is telescoping so clearance differs depending on which end is installed where. Since it's so shorter, the arm turns the steering on the second axle less than the first, and I don't need to do any servo mixing. Now my problem is with needing different trim for each axle, and I'm not quite sure how I'm going to solve it. I've been thinking up a project involving ESP32-CAM which could conceivably solve this for me, but it's not even begun yet.
One positive note on feel: I have big hands and I do wish the Tx was slightly larger, but the aluminum knob on the "metal" version feels like money well spent. It's got a really great feel with just the right sharpness to the edges. On the other hand, the thumb lever for one-handed driving feels a bit flimsy next to it, and it would have been nice to see a little more attention there. Perhaps it will come in a future version.