The new era that is Spread Spectrum

To start to explain why 2.4GHz Spread Spectrum is such a quantum leap over the system we have at present, perhaps it is best to look briefly at just that. If you’ve been flying for a while you’ll be more than aware of the problems listed below so skip forward to see how Spektrum resigns them to history. If you want more detailed information of the Spektrum system and how it works take a look at the Spektrum website. Click here to go. If you’re new to RC flying take a look at the problems you can leave behind by starting off flying at the outset with Spektrum.

Present technology

At present the majority of flying in the UK uses the 35 MHz band that is designated solely for airborne radio control. 27 MHz can also be used but is not restricted to air alone, but in that field is mostly utilised by smaller ready-to-fly types of planes. For the most part this present technology serves the modeller well but there has always been several dogged problems that consistently arise.

Frequency clashing

The radio systems that have been used up until Spread Spectrum have no frequency avoidance technology incorporated into their design. The user has to choose the frequency he wants to fly on either by the instillation of crystals, or by selecting a channel on a synthesized system. If someone else is using that same frequency at the same time within transmitter range, the resulting interference to each other will take one, or most likely both models out of the sky.
This problem is dealt with at flying clubs by the use of a pegboard of some description. Each frequency has a designated peg. When you want to use the frequency you take the peg and clip it on your transmitter. That frequency is then yours to operate on. Downside is that if someone else has the peg for the frequency your model is on you either have to wait for it to become free, or change the frequency you are on. Sometimes too, human error creeps in; someone could leave their transmitter on after returning the peg, or inadvertently put the wrong crystals in, there are lots of scenarios that can occur, that have occurred and will continue to occur.
Finally a problem that has crept in more recently is individuals buying ready to fly planes and flying them close to flying fields. Whether they feel they are being more sensible flying in an area where other models fly or not, all they really do is run the risk of knocking someone else’s plane out of the sky.

Commercial clashes

The bands we use are split into narrow channels and because of the limited range needed don’t produce a very powerful signal. Unfortunately commercial users have very much more powerful transmitters working over larger distances and although they may use channels in between ours if their equipment slips off frequency it can cause interference.

Model Generated Interference

Probably more common than most modellers realise, rubbing metallic parts, radiated interference from ESCs and a host of other sources generate unwanted RF ‘noise’. This kind of interference is generated within the range of present used frequencies and can cause, sometimes unexpectedly, anything from a glitch to complete loss of control of a model.

So Spread Spectrum solves all these problems?
Well - yes.

Radio generated Interference

At the heart of the solution to the interference issue is a worldwide agreement whereby all 2.4GHz devices have some type of ‘collision avoidance’ technology incorporated into their method of operation so that they cannot interfere with any other devices using that same frequency.
A Spektrum radio has no crystals. When it is turned on the first thing it does is to scan to see if any other similar devices are using any of the 80 channels available to it. Once it has done that it selects, in the case of aircraft, two free channels and locks onto and occupies them. This process typically takes a matter of milliseconds, so as long as all the channels aren’t taken it will just seem like turning your transmitter on. If it can’t find any free channels however it goes into a hold mode and continues to scan but does not transmit any kind of signal. Once it does find the free channels it starts to transmit a programmed unique identification code called a GUID (Global Unique IDentification). This is a code that is recognised only by its receiver and while it’s transmitting the receiver is scanning looking for that code. Once found the two lock to each other and form a solid RF link.
So it is impossible to turn on and transmit with a transmitter that is on a frequency that is already in use, impossible to have the wrong crystals installed. The old peg board is now rendered redundant but safety on the flying field, adjacent to it and anywhere that planes and helicopters are flown takes a massive leap forwards.

Commercial Clashes

Along with collision avoidance, international agreement has made it mandatory that all devices on 2.4GHZ also will have no more than one watt of output power. This is more than enough for modelling use, in fact DX6 and 7, like all commercially available modelling radio systems, only have 100 mW output. So there can be no high output transmissions to create interference as on the old systems.

Model Generated Interference

RF noise can be generated within a model by numerous things. On-board electronics, power surges, gear trains, bearings, mechanical control systems and arcing on brushed motors along with numerous other things can produce it and create real problems for modellers. All of this noise is generated under 300MHz making 35 and 27MHz systems vulnerable. Spektrum operating at 2.4GHz is way, way above this and simply won’t see any of it.

Spektrum- Just what a radio system should be

So Spektrum is the answer to the modelling maiden’s prayer? Actually it really is. With this superb system so many of the issues that have caused problems for model flyers in the past have disappeared. Not just pushed aside, but really disappeared. So with this radio you will never have to worry about getting the peg before you switch on, no more waiting if your peg is in use, no more RF noise of any type causing problems, and because the signal is purely digital, there will be no more glitches or inter-modulation issues that have caused problems in the past. With DSM they too are gone. Turn up to the field, turn on and let the technology do the work!