JR racing XS3: Synthesized FM computer radio system

Radio Control Car Action, Apr 2003 by Vieira, Peter

Channel surfer

Since RCs earliest days, the frequencies of the signals we transmit have been determined by crystals-those fragile metal pills we plug into our radios and receivers. For racers, that has meant keeping at least two extra crystal sets ready to resolve frequency conflicts at the track. Even if you aren't a racer, chances are you've had to buy at least one extra set of crystals to avoid being on the same channel as another guy at the local hot spot or to replace a set of crystals that went bad.

Well, you can forget all that. Crystal-free technology has arrived, and JR Racing is the first to offer a radio system with a crystal-free transmitter and receiver that have been designed and manufactured in-house to work together. They're part of the new XS3 package, and we've got all the test data you're looking for.

What does

this button do?

The XS3 has a thumb switch (grip button "C") that can be used for three functions, depending on your needs:

* EMERGENCY STEERING. If you select this mode, activating the switch will over-- ride the dual-rate steering setting to give you full steering throw. This is useful if you've dialed out much of your car's steering but find you need to make a U-turn to get out of a crash. If you can get back into the race without waiting for a marshal, you'll have a real advantage.

* LAP TIMER. The XS3 uses an "up timer," which means it starts at zero and counts up. Once the lap timer has been activated, each consecutive press of grip button "C" records a lap. Up to 50 laps can be stored, and you can scroll through them on the LCD screen.

* GEAR-SHIFT TOGGLE. This mode is for those who drive third-channel-reverse trucks. It activates the third servo, and each button click sends the servo to the end of its travel range (as set by you with the endpoint function).

More on that third channel ...

Grip button "C" can't be used for proportional third-channel control, but that doesn't mean the XS3 lacks this capability. If you assign grip lever "A to the third channel, it will operate the third servo proportionally when you click the switch in the direction you want the servo to go. This is perfect for making onboard fuel/air mixture adjustments in nitro vehicles (not done much in cars, but it's common in boats), or you could use it to make a wing servo-adjustable or operate "special-effects" functions. How about a rotating turret on your touring car?

Don't forget the servos

Along with the RS300 75MHz receiver, a 4-cell, AA battery holder and a switch harness, the XS3 includes a pair of servos that are a good match for any type of 1/10-scale competition.

* Z270 STANDARD RACE SERVO. This is your basic servo; it has a plastic gear train and about 40 oz.-in. of torque. This servo is best for the throttle or shifting mechanism if you drive a nitro car.

* Z590M TORQUE RACE METAL-GEAR SERVO. Here's your steering servo; with 85 oz.-in. of torque and a 0.15-second transit time, it has the juice to keep your nitro and electric trucks and touring cars pointed in the right direction.

XS3 FEATURES

The XS3 has the same primary features and case as the XR3i, which are explained in detail in February's "Product Probe" XR3i review. (No back issue? Check it out online at rccaraction.com.) Model memory has been upped for the XS3, though; it can store settings for six models, while the XR3i stores four.

* Steering, throttle and third-channel endpoints

* Six-model memory with three-character

model-naming capability

* Adjustable throttle deadband

* Steering, throttle and brake exponential

* Steering/throttle mixing

* Steering, throttle and third-channel subtrim

* Steering dual rate

* Direct trim

* LCD display

* User-assignable grip levers

* Adjustable wheel tension

* Low-voltage alarm

Don't forget the servos

Variable frame rate is the latest in RC radio technology, and it's designed to exploit the superior speed of digital servos. With the fast frame-rate setting, digital servos can respond more quickly to commands. JR recommends that you use the fast frame rate only if your car has at least one digital servo. If you use analog servos, the fast frame rate offers no advantage, so select the normal frame-rate setting.

So ... does it work? The answer is "Yes." When using digital servos, there is a difference in responses obtained with the normal and fast frame-rate settings. It isn't a dramatic difference, though; you may not feel it if you race off-road or in other situations in which the cars have breakable traction. But in situations where every millisecond counts (such as high-- traction carpet racing-especially 1/12 scale), you'll be able to feel increased quickness and precision in your steering inputs.

Changing channels

In our February issue, we gave the XR3i high marks for its ergonomics and easy-to-use functions; the XS3 feels the same and operates in exactly the same way. The adjustable wheel tension is a welcome feature

(I like mine really stiff), and the Direct Trim feature is a plus; with each click of a trim switch, the LCD screen automatically displays the function's setting.