Spread Spectrum RC

The introduction of spread spectrum technology into the world of radio control is without doubt one of the most important advances to occur in the history of the hobby.

The last major shake up of radio control systems was the introduction of Pulse Code Modulation (PCM), somewhen back in the 80s, which allows the analogue signals being sent out from a standard FM transmitter to be converted to digital signals. This results in a stronger, more positive signal with less chance of interference from either other rc transmitters or 'metallic noise' which can often cause unwanted servo glitching.

But spread spectrum technology uses a completely different method of signal transmission again, known as Digital Spectrum Modulation (DSM) and operates across the 2.4GHz frequency band, which is well clear of any of the other bands used for rc and other common radio signal transmissions.

DSM technology has been developed from Direct Sequencing Spread Spectrum, a form of secure radio signal transmission that has been in use by top government bodies (military, NASA etc.) for a while. DSM is fundamentally the same, but it's been tweaked a bit for the rc hobby industry.

DSM technology is completely closed to any form of interference whatsoever. A Globally Unique Identification Code is assigned to every radio transmitter during manufacture, and this is just one unique code out of millions of possible codes.
The receiver is programmed to identify that unique code in what is known as the 'binding process', and so the tx and rx lock together with the same GUIC, blocking out all other codes in the process. This process only takes a couple of seconds every time the set is switched on.

Once locked together, the transmitted signal is spread out over a wide band before being identified and 're-assembled' by the receiver, further increasing security.

Another big difference with spread spectrum radio control is the response time - everything happens within a few milliseconds, so servo movement and the associated model response is instantaneous and direct, a major bonus for demanding 3D flying.

What does DSM mean at the flying field?

In a nutshell, spread spectrum radio control systems let you fly your models with absolute peace of mind.
Once you turn on your system, your flying frequency is chosen for you and becomes unique to that model - no other radio signals or interference can penetrate your channel.

DSM rc systems don't use crystals so you don't need to carry a spare set of those around, and you also won't be needing to put a peg in the club frequency board before you fly!

Another safety aspect of a DSM transmitter is the antenna - a spread spectrum signal can be sent through a much shorter antenna, one which doesn't have to be extended several feet in front of you.

Spektrum RC

Spektrum are the pioneers of the 2.4GHz technology for the radio control hobby industry, and for a while were the sole manufacturers of spread spectrum rc systems. Their DX6 is a very popular choice for rc pilots looking for total security.
Spektrum also manufacture DSM modules, designed to fit into certain JR and Futaba radio systems. This is an excellent idea, as this upgrade option means that many rc pilots won't have to change to a complete new system but can continue flying on the one they are familiar with.

Futaba have also released their first 2.4GHz spread spectrum set, the 6 channel 6EX.

Where does it go from here?

Who knows!
DSM Spektrum radio control systems are very new to the hobby, but are already proving to be a huge success, not surprisingly.

With such secure signal transmission and instant model response, it's hard to imagine how radio control systems can be improved now - but think about what's happened with technology in the last few years!

With time it's probable that more Ready To Fly rc airplane and helicopters will be supplied with a spread spectrum set as standard. Currently there is only a handful of RTF models being sold as such, the Blade CX2 co-axial electric rc helicopter from E-flite being one example.

Wherever it does go from here, DSM technology is certainly going to be seen more and more on the flying field, and club frequency boards might even become a thing of the past!

Red Rocket Hobby Shop carry a selection of spread spectrum rc sets from Spektrum.

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