Controllers Style

There are two styles of transmitters: steer wheels and sticks. The choice between the two really seems to be a matter of taste, although there seems to be trends? In North America, almost everyone was using steer wheels, but here in the UK, sticks are the most prevalent. I feel like my thumbs are just, well, all thumbs, so I feel my other fingers have more dexterity, but then, people using sticks beat me all the time, so… :-)

Frequencies

There used to be a number of frequencies, in the 27 MHz and 49 MHz bands, you had to make sure no two racers used the same frequency, and tracks would each have an etiquette to follow to avoid this situation, but this has pretty all been replaced with the new 2.4 GHz frequencies. This is the same frequencies as WiFi, and radios of that generation are “frequency hopping”, which means that through some witchcraft I do not understand, they all work together without interference. So, whatever radio you get, make sure it uses the 2.4 GHz frequencies, which will make this completely simple to use.

Adjustments

Two essential adjustments are end point adjustments and exponential settings. The end point adjustments limit how much the steering servo can move, protecting it if it cannot go through its entire range of movement (this depends on the steering arrangement of your car).

Exponential settings is a bit harder to understand, but lets you increase or reduce the sensitivity around the center position, making the car easier to handle. It does not change the speed at which the servo will move, but “exchanges” sensitivity between the center and the ends of the range. For example, if you reduce the sensitivity at the center (which increases the precision, as you need more control movement to get the same servo movement), you’ll find that at the extreme, a smaller move of your controller will yield more servo movement (more sensitive, but harder to control, less precise, more twitchy). This effect is tunable, and can be non-existent, subtle, or very harsh, as you prefer.

Model Memories

This feature allows your transmitter to pair with multiple receivers, so that you can use a single transmitter with different cars. Each car will have its own set of settings (including the end points and exponential), so that you can easily jump from one car to the other.

Number of Channels

The channels are used to transmit information to the receiver. For a racing car, you need two: one for steering, and one for throttle/braking. Some other models might need more channels, if they have four-wheel steering, for example, or to control accessories (like lights, or a winch, say).

Refresh Rate

Older radios were analog, and so transmitted continuously, but a (small!) downside of the newer 2.4 GHz radios is that they are now digital, transmitting information in discrete bursts. Higher end radios will have a faster “refresh rate”, which means there will be less time between your action and the car reacting. This can vary from as little as 5.5 milliseconds, all the way to more than 30 milliseconds. This can feel a bit like “lag” in a video game, in the extreme, but 30 ms is about 33 fps, which could be better, but isn’t that bad either. Just like video games, you’ll probably find that you can adapt and “lead” the car a bit to erase the effect, but for the best experience, you would want the highest refresh rate possible, of course.

Receivers

The most important characteristic of a receiver is whether it is compatible with your transmitter! Past the basic “it works” level, some transmitter need specific receivers for some of their features. For example, with my Spektrum DX4R Pro radio, the SR2000 allows for a 5.5 ms refresh rate, but with the SR410, it is only 11 ms (but has four channels instead of two, in exchange).

Some receivers also have extended features, like telemetry (allowing to transmit back information like motor temperature or speed, etc), or driving assistances (traction control, ABS braking, stability control). Many of those features are not allowed for racing, so I did not investigate these much.

Often, transmitters will include a receiver, but check whether that is the case, as this will be an additional cost you might not expect.

Which One?

With the information above, I think you can make a decision that suits your budget, but I would add that, in my experience, radios are a lasting investment, which you can carry over from one car to the next, as you upgrade the rest of your kit. This is especially true if it has model memories, so you can save money if you get more than one car (otherwise, you’d have to buy another transmitter).

In terms of brands, Sanwa (also known as Airtronics in the US/Canada) and Futaba as known as the best, but are also the most expensive. Spektrum is also well regarded (they invented the 2.4 GHz technology that they are all using now), but for some reason, have a better reputation for airplane radios? Myself, I got a Spektrum DX4R Pro, as I found that I could get Spektrum’s top of the line radio, for less than the price of a Sanwa MT-4S (their “club racer” model, near the top of their line). It is lacking in some features (no LiPo pack, I use rechargeable AA batteries with it), but seems to have the important features, at a good price point.