From Michael James,
Your Guide to Radio Controlled Vehicles.
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When buying mass market or toy-grade radio controlled vehicles, such as those sold at Wal-Mart, Target, and other retail stores, you have a choice of two radio frequencies in the U.S.: 27 or 49 megahertz (MHz). These radio frequencies are how the controller communicates with the vehicle. If you don't plan to run your RC cars, trucks, boats, or aircraft alongside other radio controlled vehicles it doesn't really matter which frequency they use.

However, running two 27 MHz or two 49 MHz RC cars near each other will usually result in interference -- crosstalk. The radio signals get mixed up. One controller will try to control both vehicles or you'll get erratic behavior in one or both vehicles.

Preventing Radio Frequency Interference

The radio frequency of RC cars appears on the package and can be found clearly labeled on the bottom of the vehicle. With mass market RC toy cars and trucks there are three ways to avoid or minimize radio frequency interference from other vehicles.

• Keep Your Distance from Other RC Cars and Trucks
  The effective operating range for toy-grade vehicles is generally around 75 to 100 feet, although it could be more. Minimize radio frequency interference by keeping two vehicles that use the same frequency outside each other's operating range. For example, if the maximum operating range of the vehicles is 100 feet, double that amount and operate the two vehicles at least 200 feet from each other.

• Choose Separate Radio Frequencies for Each RC Car or Truck
  To operate in close proximity, make sure each vehicle is a different frequency. A 27 MHz and a 49MHz vehicle can run alongside each other with no problem.

• Choose RC Cars and Trucks With Band Selectable Frequencies
  Some toy-grade vehicles have band selectable frequencies. This allows the user to select a narrow portion or band of the frequency to use. Typically the band selectable vehicle will have a quadfrequency switch that changes between 4 different bands. In this way, two 49 MHz band selectable vehicles can operate in the same area if each vehicle (and its controller) is set to a different band.

Hobby-Grade: The Next Step in Avoiding Interference

Hobby-grade radio controlled vehicles -- usually the more expensive cars, trucks, boats, and aircraft sold in specialty hobby stores or assembled from kits -- have a wide range of radio frequencies available. Radio frequency interference becomes less of a problem with this class of RC vehicle. Some hobby models come with a fail safe device -- or they can be purchased separately -- that detects frequency interference problems and stops or slows down the RC to avoid potential problems.

Comment on your own radio interference problems or disasters