|DX6 In-Depth (Part 1)
Spektrum's DX6 sport parkflyer system utilizes patent-pending DuaLink ™ technology to create a secure, reliable, robust 2.4GHz spread spectrum link for aircraft!
You may have heard of the phenomenal 2.4GHz Spektrum system that's become the rage for R/C car operation. Now, with some important innovations, aircraft modelers can use this fantastic technology with their park flying models and enjoy all the benefits that have made 2.4GHz spread spectrum technology such a hit for surface users.
True breakthroughs don't happen very often in the industry. Fasten your seatbelts to discover the benefits of a first-of-its-kind product certain to improve safety, convenience and reliability of R/C aircraft flight.
THE RADIO SYSTEM AND ITS CORE ADVANTAGES
The Spektrum DX6 is a 6-channel computer system designed to be flown exclusively with parkflyer airplanes and micro/mini helicopters. Using 2.4GHz Spread Spectrum DSM (Digital Spectrum Modulation) technology, the DX6 system includes a nicad-equipped transmitter, a micro 7-gram AR6000 receiver, and four lightning-fast sub-micro S75 servos.
With the 2.4GHz, you can say goodbye to frequency pins, getting shot-down, or shooting someone else down for that matter. Plus, you'll never have to wait for a frequency pin again. And that's just the beginning of the benefits of operating on the 2.4GHz band.
When using this system, (which operates just like you'll never have to worry about "noise" coming from your motor or speed control (or anywhere else on your model) affecting your radio's performance. Why? It's simple. Motor and model-generated noise has no energy above 300MHz. . Your DSM system operates nearly eight times higher in the frequency range (see chart.) Fact is, you can mount your AR6000 receiver directly to any speed control. It just doesn't care and won't be affected a bit.
And because the signal is pure digital, it means that glitches are a thing of the past too. No more annoying glitches that shatter the confidence and cause you to worry about crashing. They're a thing of the past too.
Not to mention the nasty intermodulation issues that have plagued 27, 72 and 75 MHz like 2IM, 3IM and adjacent frequency. They too, can't affect DSM.
And to top if off, the equipment you see here is all solid state. There are no pots to tune, nothing to ever degrade in performance, adjust or need tuning.
Just the way a radio should be.
HOW DSM 2.4GHz WORKS
To understand the full benefits of the DSM system and its operation in the 2.4GHz band, it helps to review the 72MHz band we're currently flying in, and compare how the FCC rules are different between the two.
As you know, our 72MHz channels are spaced in 20Khz spacing. Our output is limited to 750mW (most manufacturers have output a lot lower than this to avoid intermodulation (inadvertent mixing of signals.) That's all fine and dandy, but FCC authorized high power industrial users to locate right in between our channels. Now, undermost situations, this isn't a big issue. Our receivers have to be very selective and sensitive to "find" our low power output signals. Normally, everything works well. But occasionally, industrial transmitters (some of these put out 50,000 Watts and more) can slip a bit off frequency. Guess who gets hit? (That said, it'd only be realistic to point out that most of us who analyze radio interference find model-generated noise is a much more common problem than high-powered industrial operators. But does it happen? Sure.)
FCC adopted a similar system with the 900MHz band - they mixed high power, narrow band users. It worked pretty well, but not perfectly. So when FCC devised the 2.4GHz rules, they set about a completely new system: they mandated that all 2.4GHz devices will transmit at less than 1 Watt. This prevents high power transmission from causing interference over great distances.
The FCC also mandated that transmitters using Spread Spectrum must have the ability to check for, and find an open frequency on the 2.4 band (there are 80 channels, spread in 1MHz spacing.) before transmitting any signal.
So when you turn on your DX6 transmitter, it scans the 2.4GHz band and picks two frequencies which show the least activity. That's right, there two frequencies used with the DX6 system. (see explanation of DuaLink technology.)
Since all devices on the 2.4GHz band are required to avoid other users (or else they wouldn't receive FCC type acceptance) there is no chance that another type of device using 2.4GHz can cause an issue with your radio. It just can't happen. They all work by the same rules.
(For more information on the Spread Spectrum story, see Dan Williams article in July Model Aviation.)
HOW EACH RECEIVER RECOGNIZES ITS TRANMSITTER
|How Each Receiver recognizes its transmitter:|
Instead of using a bind button like the surface Spektrum receiver, the AR6000 actually uses a plug to put the receiver into the binding mode. Simply plug the jumper in, hold down the DX6’s bind button when you turn it on, and bingo, its setup. Things don’t get much simpler than this.
Each Spektrum transmitter has a GUID (Globally Unique Identifier) code. Binding is the process of programming the receiver to recognize the GUID of a single, specific transmitter. Binding teaches the receiver the specific GUID of that transmitter so that the receiver will only listen to the information from its previously bound transmitter and ignores everything else. With over 4.2 billion GUID codes, the chances of having a interference from another transmitter is virtually impossible.
It is usually only necessary to bind the receiver once. The only time it'll be necessary to re-bind is if you wish to use a different transmitter, or you want to change failsafe positions (see next section.)
How tough is it to bind? Not very. Just….
1) Put the bind plug into the BAT port of the receiver
2) Power up the receiver
3) Press and hold the bind button on the back of the Tx while turning on the transmitter.
That's it - nothing complex or mysterious.
STORING FAILSAFE POSITIONS
Even with electric park flyers it makes sense to have a low-throttle failsafe. Sure, they don't have much energy, but failsafe pre-set is just plain good safety. So the DX6 has Failsafe.
You can set any channel you wish, but normally we just put the throttle to low position during the binding process. All other channels go to the last commanded position.
DIGITAL SIGNAL FEELS "LOCKED IN"
Because DSM is a fully digital signal, you'll never have a glitch. That alone will make it worth its weight in gold to any flier using sub-standard FM equipment.
But several of our testers said they felt more "locked in" to the airplane than ever before. The crisp response delivered a feeling unlike the systems they were used to flying.
There's only one way to find out - prove it to yourself!
DSM USES DIRECT SEQUENCE SPREAD SPECTRUM
You've probably heard of the familiar form of Spread Spectrum called "Frequency Hopping." This form uses a system that has the signal transmitting on one of the 80 available frequencies for just a few milliseconds, then hopping to another channel, and so forth. This is all done randomly and so fast that it won't' affect other "hopping" systems, nor direct sequence.
Our system, over five years in development, started out using a frequency hopping system. But the limitations of this format in regards to robustness of the link and slow speed sent our designers into the Direct Sequence side. Whereas frequency hopping is "old technology," the newer Direct Sequencing offers a much more robust RF link, faster speeds - yet it is exponentially more difficult to program. And it's the programming where all the magic is. Understanding what to do with hardware is the "secret" to DSM Spread Spectrum technology.