What Are DSM RC Controllers and Receivers and What Do They Do?

RC vehicle DSM receiver
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DSM or "Digital Spectrum Modulation" is a relatively new radio technology adapted to the RC vehicles world and being increasingly found as an option in RC airplanes, helicopters, cars, and trucks.

In geekspeak, DSM technology is an optimized version of Direct Sequence Spread Spectrum, also referred to as FHDSS "frequency hopping digital spread spectrum" technology. This optimized digital, crystal-free two-way communication technology eliminates and is immune to the cross-interference common with traditional radio frequency transmitters and receivers. The response time of DSM controllers and receivers is both impressive and reliable. Now that DSM technology had been incorporated into the RC world, RC enthusiasts can enjoy a safer, more rewarding radio controlled racing experience without the frustration of radio frequency interference.

DSM Compared to Traditional Radio Systems

Traditional radio systems used with RC vehicles incorporate a receiver (in the car) and a hand-held controller or transmitter that each contains a crystal set to a specific frequency band and channel. One of the side effects of this crystal-based technology is crosstalk or radio interference. This poses a problem if two vehicles are using the same crystal set and are within radio range of each other and they are both turned on. One or both of the RCs may behave erratically or begin taking instructions from the 'wrong' controller.

DSM controllers and receiver don't have this crosstalk problem, which makes them a great solution to the most common problem with RC vehicle radio systems to date.

How DSM Works

There are two main broadcasting methods that spread spectrum manufacturers can use: FHSS or DSSS.

  • FHSS (Frequency Hopping Spread Spectrum) is a type of system where the controller transmits a narrowband signal and rapidly hops from one frequency to the next. The time that it takes to hop from one frequency to the next is only a couple of milliseconds. This FHSS system is what was first used and although helpful, it had several limitations that made it not as reliable as DSSS.
  • DSSS (Direct Sequence Spread Spectrum) is the better solution and is way more reliable than FHSS type systems. DSSS systems operate on a single frequency but on a very wide band. Only a small portion is used to transmit special encoded data to the transmitter or receiver module. Also, with DSSS there are significant increases in range capability.

For Hobbyists

All RC vehicles would benefit from DSM technology. However, the use of this technology is most useful for hobbyists that fly or race in large groups where frequency interference is a major issue. DSM allows organized (or impromptu) RC competitions to accommodate larger numbers of participants at one time.

A DSM Controller/Receiver Setup With a Traditional RC

While there are currently only a few Ready-to-Run RCs that come with the DSM radio systems, there are certain modules that you could buy to adopt a traditional radio system to use DSM technology. The DSM controller has a receiver module that installs in line with the traditional radio's receiver so that the DSM controller communicates through the receiver to the rest of your electronic components installed in your RC vehicle.

DSM Transmitter and Receiver

Now that you have this new piece of radio technology, you can't just turn it on and go. You have to perform a few steps to get your controller to lock onto the receiver. The process is called binding. The DSM receiver has to search and recognize the DSM transmitter's GUID code and lock into it. This process has to be done on every module you plan to use with this transmitter or receiver. Once the receiver or transmitter locks in, a special software which helps prevent a collision for the given frequency takes over and further helps eliminate frequency interference. This software, incorporated in both the transmitter and receiver, is required by the FCC and must be installed to help prevent a collision of frequency channels and illegal use of a particular frequency channel at the same time by more than one controller. In other words, the DSM transmitter/receiver and the software do the work for you of setting the proper frequency—no need to change crystals or find out what frequencies are currently in use at your local RC track.

Other Features and Accessories

Accessories available for DSM type controllers and receivers add a few helpful features including:

  • Ability to tell you how much runtime your battery pack has left before shutdown.
  • Timing your laps to give you a general idea how to tweak your RC for optimal racing conditions.
  • For all you nitro RC owners, this option is for you: The ability to give you feedback on how hot your nitro is running to help with tuning for optimal performance. How cool is that?

Buy DSM Modules and Controllers

Currently, DSM modules and radios range in price from around $40 to hundreds of dollars, depending on features. Usually, the more channels, the higher the price.

  • E-Flite LP5DSM 5-Channel Transmitter, 2.4GHz BCX2
  • JR X9303 9-Channel DSM Radio
  • ParkZone Vapor with Spektrum DSM2
  • Spektrum Air Modules (for converting RC aircraft radios to DSM)
  • Spektrum Surface Modules (for converting RC car and truck radios to DSM)
  • Spektrum DX5e, DX6i, and DX7 Air Radios
  • Spektrum DSM Surface (Pistol) Radios
  • Losi LSR-3000 DSM Transmitter
  • MTX Pro DSM Transmitter