One subject that comes up frequently when learning how to operate multiple RC cars at once is the subject of radio frequency interference. If two remote controlled cars are set to the same frequency, this means that they can’t be operated at the same time.
So how do you change the frequency on your RC car? Some RC cars can have their frequencies changed with RC crystal sets. With a crystal set from an electronics store or RC supply shop, you can exchange the crystals in both the receiver board and the remote control to set the car to a different frequency. Some RC vehicles have an option to change frequencies built in to the vehicle as well.
Changing the frequency on your RC car can be a little tricky, but if you have the right supplies, it isn’t impossible. Keep reading to find out more about how you can modify your RC car’s frequency.
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How Does Radio Control Work?
To understand how to change the frequency on an RC car, you really need a crash course in how radio control works. Radio control is used to remote control a variety of small motorized vehicles, from RC cars and boats to helicopters and even surveillance drones.
Radio controlled motorized vehicles operate on the basis of four fundamental components:
- Radio transmitter: The radio transmitter is the component of a remote control that sends out a radio frequency that is interpreted by the RC vehicle as controller data.
- Radio receiver: The radio receiver is the component of the radio control located in the
RC vehicle itself, and (as the name implies) receives radio signals and delivers them to the vehicle’s motor.
- Remote controlled motor: The motor in an RC vehicle is the part of the machine that operates its wheels, propellers, etc. by converting fuel or electricity into mechanical energy.
- Power source: The power source is the source of energy that drives the motor or the remote control. Remote controls are often battery-powered, while RC motors can be either electric motors or fuel-based motor systems.
Unless all four of these components are operating properly, the RC vehicle will not be function. To operate via radio control, the radio transmitter in the remote control sends out a signal to the radio receiver located in the RC vehicle, either activating the motor electronically or controlling the flaps on the carburetor in a fuel-based RC system.
What Frequency Do RC Cars Use?
Most RC cars operate on one of two frequencies: 27 MHz or 49MHz. This is because these are the two radio frequencies designated by the Federal Communications Commission (FCC) for small appliance remote control use such as hobby RC vehicles, garage openers, and lighting systems.
There are some advanced RC models that operate at 72MHz or 75MHz, but these models are more sophisticated and rarer than the RC cars most hobbyists will be exposed to.
The reason that RC cars operate on a standard radio frequency is that if they are adjusted to operate on a different frequency, this can cause serious issues with radio signals used in television, wireless radio, and other forms of communication. Depending on what devices are affected by the radio frequency interference, this interference can potentially even be dangerous.
For this reason, you should check the legality of modifying radio frequencies on any RC vehicle you’re using and make sure that you’re in compliance with the FCC’s regulations regarding RC use before you start attempting to change the frequency it operates on.
How Do RC Controllers Work?
RC controllers operate by sending out electrical impulses that correspond with actions that are pre-programmed into the radio receiver board in the RC car.
The RC controller operates off a different power source than the RC car—the standard power source for the RC controller is a nine-volt battery, while the RC car operates off either a rechargeable lithium-ion battery or a fuel-based system. This battery is required for the controller to be able to emit radio waves for the receiver on the RC car to pick up.
Once the RF signals are sent out, the receiving board in the RC car picks up these electric pulses wirelessly and translates them into motorized action. In RC cars, this translates to the car’s wheels propelling it forward or activating the brakes and steering.
As mentioned earlier, changing the frequency on an RC car has to be done at both the transmitter end and the receiver end for the RC car to be able to correctly receive and translate signals, so if you’re going to change the frequency on a crystal-controlled RC vehicle, you’ll need to change crystals in both devices for it to work.
Crystal-Controlled Receiver Boards
In RC cars, the crystal in the transmitter and receiver parts of an RC system are what determine which frequency the system is attuned to. Sounds sort of like something out of a fantasy novel, doesn’t it? In actuality, the answer to how this all works is a lot more scientific.
The truth is that piezoelectric crystals are used in radio technology to modulate between electric and mechanical energy. In acting as a diode in the RF system, a crystal both detects radio signals and modifies them into a form that can be interpreted into mechanical energy. It does this by “rectifying” the signal and smoothing it out, making it easier for the receiver to read.
In RC technology, radio crystals are typically soldered to a small circuit board where they then act as a timebase generator to synchronize the frequency transmitted and received between the two devices.
It is important to note that crystal sets can only be used to make very minor adjustments to an RC car’s frequency, such as changing it from one channel within a frequency band to another.
What Does 27MHz Mean on an RC Car?
27MHz (or megahertz) is the most commonly found frequency used in RC vehicles. In order to offer flexibility to users, consumer-grade RC cars are often designed to function on both 27MHz and 49MHz frequencies. These are also the two frequencies standardized for RC use by the FCC.
This is because if you operate two RC cars together in a race and they’re both set to the same frequency, radio frequency (RF) interference will prevent you from using either car effectively. To avoid this problem, RC car manufacturers usually make it easy to modify the frequency of one of the cars to 49MHz so that both RC cars can be operated simultaneously without RF interference.
This interference between multiple RC cars being operated simultaneously is one of the biggest reasons that people look to try and change the frequency on their RC cars.
What Do You Need to Change the Frequency on an RC Car?
If your issue with changing frequencies is that you’ve got two RC cars on the same frequency and their crosstalk is making operation impossible, there’s a chance you don’t have to do any serious modifications to the vehicle. Some RC cars come with selectable bands, which means they operate on several frequencies within the range of 27MHz. Here are six common bands utilized in the United States for RC vehicles:
- 26.995 (Channel 1)
- 27.045 (Channel 2)
- 27.095 (Channel 3)
- 27.145 (Channel 4)
- 27.195 (Channel 5)
- 27.255 (Channel 6)
With selectable bands, you should be able to flip the car’s designated frequency from the default frequency to one of the alternate frequencies. As long as the two vehicles are operating on different channels on the 27MHz frequency range, they should not interfere with each other’s operation.
If you’re trying to modify the frequency in a transmitter in order to be accurately received by an RC car on the same frequency, whether you’ll be able to pull it off will depend on a few different factors. If your receiving board has a crystal, but the circuit board on your transmitter doesn’t, you’re not going to be able to modify that particular controller to work with the car.
Cheap Chinese Controllers are Difficult to Change Frequencies On
In general, the receivers in RC cars are not designed to be quartz-tuned with the precision you need to completely reset the RC car’s frequency, so unless you’re prepared to change the coil as well or make some serious adjustments to the car’s circuitry, you’re going to have a hard time getting the two components to sync up.
For someone to have any luck changing frequency on a transmitter-controller, it pretty much has to be set up for multiple frequencies in the first place. If you open up your controller, there should be a label inside on or near the circuit board stating what frequencies the controller can be operated at, even if it doesn’t have a band selector switch.
This default radio channel should also be designated somewhere on the outside of the controller or in the RC manual. With most RC vehicles, the only viable option is to modify the frequency from 27MHz to 49MHz, and even this is not done easily.
If you decide to open up your remote control to adjust the frequency, be very careful. Many cheaper Chinese remote-control models are designed as a sealed unit, so breaking them open in an attempt to adjust the frequency can effectively destroy them.
Cars on the Same MHz Frequency Can’t Be Controlled Together
The video below illustrates the main problem with having multiple RC cars operating on the same frequency—if both vehicles operate on the same frequency, they can’t differentiate which vehicle the wireless signal is intended for. Luckily, it also illustrates a simple fix for the problem.
Changing the frequency of an RC car becomes crucial in situations like competitive RC races, where several RC cars will be in operation at the same time. Only by setting each car to one of the sub-bands in the 27MHz frequency will allow you to race them simultaneously without RF interference.
Can You Run Two 2.4GHz RC Cars at the Same Time?
Some RC cars operate on a gigahertz (GHz) frequency range rather than a MHz range. There are two major benefits of using a GHz ranged RC vehicle vs. a MHz vehicle:
- Range: RC systems that operate on a GHz frequency can receive a signal from a much greater distance than those that operate on a MHz frequency.
- Reduced interference: RC systems that operate on a GHz frequency are less likely to receive crosstalk or radio interference from other RC systems since there is less “chatter” on a GHz frequency than the standard 27MHz frequency used in most RC applications.
When you’re operating RC cars on a 2.4GHz frequency, you pretty much don’t have to worry about any kind of interference. Because GHz transmitters are designed to “bind” with a signal receiver using a unique electromagnetic signature, there is none of the RF interference between GHz-based RC models that you see between MHz RC models.
Can You Convert an RC Car from 27MHz to 49MHz?
Unfortunately, a crystal set alone cannot be used to change an RC car from 27MHz to 49MHz (or to any other major frequency band). This is because crystal sets are only used to make minor adjustments to an RC car’s frequency, such as changing a car’s frequency from 27.145 to 27.045 to reduce radio interference between two units.
To change an RC over from 27MHz to 49MHz, you not only have to change out the crystals in the receiving board and the transmitter, but you also have to pretty much rewire the circuitry of the entire system and replace the capacitors, coils, and even servos in order to make it work. Cost aside, it’s rarely worth the trouble.
Even if you can manage to change the frequency for both the transmitter and receiver to the same frequency band, the range of the two units can still be significantly reduced unless the RC system is re-wired completely.
Upgrading the Radio Equipment on Your RC Car
In some cases, either due to sentimental attachment to a certain RC vehicle or a desire to learn the ins and outs of RC customization, it can be desirable to upgrade part or all of the radio equipment associated with your RC car rather than purchase a new one.
Here are some of the upgrades you can make to the radio equipment on your RC car while you’re changing the radio frequency it operates on:
- Converting from a wheel-and-trigger RC controller to a stick radio controller (or vice versa)
- Upgrading to a more dependable manufacturer’s equipment across the board to avoid reliability problems associated with cheaper models
- Adding telemetric components for real-time analysis of speed or other driving variables
- Upgrading to a transmitter with model memory so that you can operate several vehicles on one controller
- Installing additional radio channels for specialized control input
RC vehicles have been around for decades now, and as a result of the culture building up, there are tons of options for you to modify the radio equipment on your RC car to improve its performance. You just have to know what you’re looking for. Here are some questions you can ask yourself about the kinds of upgrades you want to make to your RC car:
- What kind of range do I need?
- What kind of controller layout do I prefer?
- What frequency do I want to operate at?
- How many RC cars do I need to operate at once?
- Does my RC car require any kind of specialized steering or controls?
Once you’ve answered these questions, you’ll have a better idea of what RC customization options or modifications can help you achieve your goals in the hobby.
Is Adjusting the Radio Frequency in RC Cars Safe?
When people uneducated in radio science hear words like electromagnetic radiation, they might have images in their head of paranoid people wearing tinfoil hats or (worse) people who have been exposed to nuclear radiation poisoning. They may also be concerned about cancer as a result of environmental RF exposure.
Since radio waves are a form of radiation, many people confuse dangerous ionized radiation and environmental RF radiation, which is non-ionized.
Regardless of which frequency you decide to swap your RC car to, you’re not in any danger from the electromagnetic radiation associated with radio frequencies and RC or wireless radio systems. There have been no conclusive studies to show that proximity to the kinds of radio frequencies involved in RC systems causes any kind of damage to people, or puts them in any sort of danger.
In fact, despite the efforts of some people to the contrary, most people in modern society are effectively surrounded by environmental electromagnetic radiation all of the time, due to the pervasive nature of wireless technology in our culture.
Before Attempting to Change RC Frequencies, Have an Idea What You’re Doing
Overall, unless you’re planning on making a simple adjustment to an RC car within the 27MHz band, changing the frequency on an RC car to a completely different frequency range often involves more electrical engineering prowess than most hobbyists are capable of.
For many commercial grade RC cars, swapping to a separate frequency channel can be as simple as flipping the band selector switch. In RC cars that don’t have a band selector switch, crystal sets can be used to make this kind of minor adjustment. For a complete conversion to a separate frequency, you’ll need a lot more electrical knowledge.
To get more background on how RC radio systems work, check out the video below.