RCU Review: Spektrum DX3 DSM


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    Contributed by: Eric Hege | Published: September 2005 | Views: 128628 | email icon Email this Article | PDFpdf icon
    Spektrum DX3 DSM


    Spektrum

    Distributed Exclusively By
    Horizon Hobby, Inc.


    4105 Fieldstone Road
    Champaign, IL 61822 USA


    Phone: (877) 504-0233
    Fax: (217) 352-6799
    Website: www.horizonhobby.com


    Collision Avoidance
    Uses 2.4GHz range
    79 Frequency Channels
    Short Antennas


    Lacks Some Advanced Features
    Only Three Memory Slots

    In the beginning, radio manufacturers created the radio and the receiver. They said, let there be control, and there was control. They said let there be crystals, and there was crystals to divide one channel from another. The radio manufacturers saw this, and knew that it was good.....

    Well, maybe that wasn't exactly how it happened, but there can be no denying the fact that the radio segment of the hobby has been on a very progressive march for the past few years. Synthesized radio operation became the hot thing to have a few years ago, and it heavily impacted the RC scene overall. Now its time for the next wave of progression, with the advent of spread spectrum technology specifically for the RC industry. Within this progressive charge is a company called Spektrum. They first offered compatibility for module-based radios, and now a complete radio package known as the DX3.

    The DX3 offers many of the standard features most of us look for, but the biggest advantages are claimed to be in what hasn't been offered up until recently. That's the ability to completely eliminate glitching and channel conflicts altogether. That's a tall order, but one that Spektrum feels they have satisfied.




    Model: Spektrum DX3 DSM
    Part Number: SPM2030
    Channels: 3
    Price: $250.00 (Approx. Street Price)
    Modulation: Digital Spread Spectrum
    Band: 2.4 GHz
    Servos: Z590MG, Z270
    Receiver: Spektrum SR3000 DSM 3-Channel
    Model Memory: 3 Model Memory
    Radio and Receiver
    Documentation
    Servos

    Probably the first thing you'll notice when you open up the box containing the Spektrum DX3 is the lack of a long collapsible metal antenna. It has been replaced by a plastic antenna that stands only a few inches high and folds down to protect it during storage. The silvery-gray finish helps delineate the radio from all the standard black plastic ones you see at the track, while the layout of the radio itself ushers back memories of the JR XR3. A very small matching receiver is included as well.

    As you would expect, the Spektrum is provided plenty of good documentation to help you get up and running. The main manual covers all of the features and general operation of the radio, including things such as endpoint adjustments and radio/receiver binding. Most of the features are items long time hobbyists are used to, but binding is something altogether different and new to the scene. It involves making sure that the radio and receiver are operating on a channel that no one else is using, and therefore an integral part of what's termed collision avoidance. Binding is something we'll discuss in a little more detail later.

    An addendum to the manual covers the aspects of throttle and steering mixing. In most cases these probably won't be used for a land-based vehicle, and are more often associated with marine-based vehicles. However, regardless of the need, the DX3 has the capability of mixing channels, and the documentation is provided to help you utilize the feature. So if you need to utilize it, you'll have an explanation of exactly what you need to do to set it up.

    What Makes DSM Technology Different?

    The most important thing regarding DSM technology is that it transmits in the 2.4GHz range. This range is well out of the frequency ranges that normal interference occurs on, which is generally below 300 MHz. This means that glitching due to things such as bad bearings and electric motors are a thing of the past when operating at this high of a frequency.

    Another benefit is the fact that the 2.4 GHZ frequency range is legal for use in both the U.S and overseas. So if you travel overseas to international events, you'll find that a radio equipment change is no longer necessary.

    Also, due to the short wavelength of a 2.4 GHz signal, the antennas on the radio and receiver are much shorter than what's typically associated with standard radio equipment. This means you can drive without a big metal rod in front of your face, and you no longer will find it necessary to have a long antenna dangling out of your car or truck body.

    The included servos should look very familiar to those who have used some of JR's products in the past. These are the same servos that come with the JR XS3 and XR3i, but have been re-badged with the Spektrum label. The Z590 is a high-torque metal gear servo, while the Z270 is a standard plastic geared servo. The Z590 will work well for steering purposes such as a stadium truck but, with the fact it offers only 85 oz/in of torque, you may prefer something a little stronger when it comes to steering around a large monster truck. The Z270 is targeted more to the need for a throttle/braking servo, and offers 49 oz/in of torque.

    Accessories
    Antenna Length
    Steering Tension

    The included accessories are what you would normally find in a radio/receiver combo. You'll get a set of servo horns to assist you, should you need them for the servo linkages, as well as a power switch and AA battery holder. Typical items, but often very necessary.

    We mentioned antenna length earlier, and it's often one of the first things someone notices. The radio itself comes equipped with a antenna made of plastic. It measures 3.5 inches high when it's raised up and, to help protect it when it's not being used, the antenna folds down on a hinge at its base.

    The receiver itself makes use of a shorter than normal antenna as well. The antenna wire measures 8.5 inches in length and can be cut down to a height of 3.6 inches if you desire. This makes it easy to mount under a vehicle's body, eliminating the need for the antenna to poke out of it. In addition, the receiver's case allows you to route the antenna wire out of the side instead of going out the top as it does in the stock configuration.

    If you like some steering feedback, in the form of tension at the steering knob, you'll be glad to note that the DX3 transmitter provides you with an adjustment screw for this very item. I'm a big fan of this myself, as some tension at the steering wheel helps me from overturning it when I'm controlling a car or truck. Turning the screw clockwise increases the steering tension, while turning it counter-clockwise decrease steering tension.

    Charging Jack
    Normal Display
    System Mode

    If you want to use the Spektrum DX3 along with a wall charger and a transmitter pack, you have that capability, thanks to a charging jack built into the front of the unit. However, keep in mind that this jack follows the same polarity configuration as JR radios do. This means that the jack is reverse polarity. So you'll need to make sure that any charger you use follows this as well, otherwise you can damage the transmitter pack and radio. This is especially important due to the fact that this is backwards of most other radios on the market.

    The Normal Display Screen is what you are greeted by when you first switch on the radio for use, and when you are operating your vehicle. In the upper right-hand corner of the screen, a programmable three character name for the memory setting you are using is displayed. The DX3 offers a total of three nameable memory slots, which I find a little on the weak side considering the larger number offered by most radios on the market now. Underneath the model name is a reading providing you with the current voltage level of the transmitter's power source.

    System Mode on the DX3 is accessed by holding down the Mode and Channel keys while switching the transmitter on. While in this mode you can alter the names of the three memory slots, or you can setup the mode used by the third channel. You can also copy or clear data within the three available memory slots as well.

    Function Mode
    End Point Adjustments
    Dual Rate

    Now that we've covered the basics, it's time to get to the good stuff. That being the adjustments you'll most likely find yourself using while working closely with the vehicle you have installed the DX3 into. You'll access these settings through the function mode of the radio, and the setting you are currently working with is displayed on the radio's display clearly identifying it.

    End point adjustments, or steering travel, are a common item to work with, especially if you're a nitro guy. The ability to adjust the endpoints of the steering servo are very helpful, but even more so when it comes to the throttle/braking servo for a nitro car or truck. You can quickly damage a servo by having it try to turn beyond what it allows when the carburetor is open, so being able to control this certainly has its advantages. On the braking side of things, an adjustable end point allows you to adjust the strength of the brakes. You can even dial in more braking action to accommodate for brake fade if it becomes necessary. Also keep in mind, in regards to braking, that it is also possible to utilize a panic brake setting using grip button A.

    The DX3 also offers a dual-rate adjustment as well, which at first glance may seem similar to the end point adjustment. However they are two different types of adjustments, and will affect the vehicle differently. The end point adjustment allows you to tailor the servo endpoints independently. So one end point could be set at 50% of the left throw, while the other at 100% of the right throw. Dual-rate affects both endpoints the same. So if you set the dual-rate at 50%, both sides ability to turn will be cut by 50% of what they normally would be able to turn based upon the endpoint settings. This gives you the capability to quickly dial the same amount of steering out of the servo completely, should you need to prevent yourself from over-steering the car. It also provides you finer control with what steering you have left, as the full turn on the steering knob controls less of a turn on the servo.

    I should mention one thing in regards to the dual-rate adjustment on the DX3. Just like with JR radios, the dual-rate setting comes set at 70% out of the box. So keep this in mind when installing it into your vehicle. I often see owners complaining about the fact they don't have the steering that they did previous to the radio swap, especially when it comes to monster trucks. The factory setting is the cause for this. My suggestion is to set the dual-rate at 100%, and then set the endpoints where you want them. Then as you drive, back the dual-rate setting down as needed.

    Sub-Trims
    Servo Reversing
    Direct Trim Buttons

    Most anyone who has used a radio transmitter before should be familiar with the trim adjustment. However, the DX3 offers more than just the standard trim adjustment in the form of a sub-trim function. While trim allows you to adjust the servos center point, sub-trim allows you to do so in an even finer regard as sometimes even one "tick" of a trim button is too much of a change to perfectly center the servo.

    As is typical with most radios, you are given the capability to reverse the servo channels. This ensures that you can accommodate any brand servo, as well as any mounting method the servo may have had to utilize. This is often handy in regards to electronic speed controls, as what your radio thinks as forward may not be the case for some speed controls. You are able to reverse any of the three channels the DX3 offers.

    The DX3 offers a direct trim mode as well, making trim adjustments available via the switches placed above and to the right of the steering knob. Moving these switches adjusts the trim setting appropriately, and an audible beep is heard to signify the change. On the grip, you'll find two other switches that offer the same type of access to the dual-rate setting, and the third channel functions.

    Grip button A can also be set to function as a shift selector for vehicles with this capability. The third channel can be setup to move a servo to a maximum of three positions, or even control a fuel mixture servo if needed with a boat. However, keep in mind if the third channel is used for one of this alternative functions, grip button A will no longer control the panic brake setting.


    Receiver Installation
    Receiver Binding
    Radio Binding

    The first thing you'll need to do when changing out your radio equipment is to install the receiver in your vehicle of choice. For my example, I'm installing it into a Duratrax Evader ST Pro. Use some double-sided tape or Velcro to hold the receiver in place. If the receiver will be installed in a roomy radio box, I would consider wrapping it in foam or bubble wrap to isolate it from any vibrations the vehicle may encounter while it's being driven.

    After the receiver is installed and wired up, you'll want to bind the radio and receiver to each other. Binding is the process by which the receiver identifies its respective transmitter. So install batteries into the radio, and power the receiver with whatever method is appropriate. In my case, it was via the Super Rooster being installed in the Evader Pro as well.

    To start the binding process, push the blue bind button on the receiver while turning it on, or supplying it with power. Once the LED beside the button flashes green, simply release the bind button.

    Now, ensure that the radio's steering knob and trigger are in the positions you want them in should the vehicle lose the signal from the transmitter. For instance if you accidentally switched the radio off while driving, the built-in failsafe could be set to apply the brakes to prevent a runaway.

    Once you have the failsafe positions set as you want them, press and hold the clear bind button on the back of the radio while switching the radio on. Once the bind button on the radio flashes green, release it. Then a few seconds later, the lights on both the radio and the receiver will quit flashing a light up solid green, indicating a successful bind between the two units. At that point, you're ready to go.

    You may wonder what would happen if two people tried binding their receivers at the track, at the same time. Unless they were within a few feet of each other, you would never notice. This is because range is limited, during the binding process, to avoid this exact type of scenario. So the likelihood of this occurring is minimal, as you'd probably know if someone pitting next to you was binding his radio. Also, given the fact that this is normally only performed once, most drivers would perform this step before they reached the track.


    After installing my DX3 I decided to test it out at the worst possible location I could think of, the local track. RC tracks can be a rough location when it comes to frequency channels. If it's crowded, with plenty of guys wanting to run, they'll soon be more punching, screaming, and cursing worse than a bunch of soccer moms at a Toys-R-Us Thanksgiving Day sale. Well, OK, maybe I exaggerated a "tiny" bit. Nothing compares to those early morning women looking for that exclusive bargain on a Game Boy. However, the fact remains that with a limited number of channels, getting some driving time at larger tracks can be awfully tough at times.

    A crowded environment is where the DX3 shines brightest. This is because the DX3 has a total of 79 frequency channels available for its use, and each one of these is way beyond the 75MHz range that the tracks normally use. So the first thing I was greeted with was the fact that I didn't have to even make the walk to the frequency board. No pins, no channel changes, and no crystals. All I had to do, once I was ready to run, was to switch on the radio and go.

    While I knew that I wouldn't have to deal with the frequency issues, once I was driving I was greeted with some other things as well that were unexpected. The first was the response time from the radio. While piloting my vehicle around the track, I noticed that the response seemed extremely crisp compared to some other radios I have in my arsenal. While the radio and transmitter have a much lower response time than most other equipment on the market, you would think that you wouldn't notice the difference between a few milliseconds. However, you can, and you don't realize it until you experience it. I felt much more in tune with the vehicle I was driving, whereas before I had gotten used to a little more lag time and had grown accustomed to it.

    I also attributed this level of control to the fact that since the radio operated in the 2.4 GHz range, it wasn't picking up on any interference from the various linkages of the nitro cars on the track, nor from any of my onboard electronics. Later, I would verify this by installing the radio into my Traxxas Revo. Once installed, I took a screwdriver and slid it up and down the various servo linkages. Normally, this would cause the servos to twitch like crazy. However, with the Spektrum installed, they didn't even flinch.

    The radio itself was also more comfortable to hold than I had previously expected. When I first opened the box, I was a little disheartened to see that there was no foam grip installed on it from the factory. Instead, I was greeted by a stock square-like plastic grip. However once I began using it, I quickly noticed that it felt much more comfortable than it had first appeared. While I realize that grip comfort is a subjective feeling, and everyone is different, I rather liked the way the radio felt in my hand. This also remained true when I used it for extended periods of time. The fact that I had no longer had a metal antenna sticking up from the radio, in my field of vision, helped with the overall comfort level as well.

    In using the Spektrum over the course of the next few weeks, I noticed one other important factor. That was the battery life of the radio itself. I had been using the transmitter pack from my JR XS3 to power the Spektrum DX3, and I noticed that I was easily seeing about 45 minutes longer runtimes before the low battery warning would have kicked in on the JR XS3. Spektrum said the transmitter has less current draw while it's being used, and they certainly meant it!

    On the receiver side, Spektrum states that the receiver uses slightly more current draw than a typical FM receiver. However, my receiver pack runtimes seemed to fall within the same length of time as they always have. So any difference is negligible from what I could see. With a 1200mAh pack, I normally get see close to two hours of runtime. That time frame remained the same with the Spektrum installed in my Revo.

    I should point out that, unlike the RS300 receiver that comes with the JR XS3, the SR3000 receiver that comes with the Spektrum package does not have a BEC built into it. In the aspect of servo performance, this is a good thing. The RS300 cut the voltage to the servos down to 4.8 volts, hindering their overall performance. The SR3000 does not, and can function at power levels up to 9.6 volts. However, with an electric powered RC vehicle you'll want to keep this in mind and make sure your speed control provides a BEC circuit to avoid damaging your servos. You shouldn't find this to be a problem though, as most speed controls do.

    While the radio was installed in the Revo, I opted to test out its built-in failsafe a few times. This consisted of me driving the Revo away from me, and then simply shutting the radio off. The failsafe promptly kicked in each time, applying the brakes where I had set them when re-binding the failsafe settings specifically for the Revo. Keep in mind that re-binding isn't necessary when you move the receiver to another vehicle, but it is the only way to alter the failsafe setting. So re-binding in an instance such as this is advised.

    Some veteran's may miss a few features that are found on higher end radios, so the DX3 isn't going to be considered an upgrade when compared to those budget busters. Some features like lap timers, throttle deadband, and exponential are missing from the DX3's feature list. If you are an owner of a high end radio such as the Airtronics M8 or Hitec Aggressor CRX, I wouldn't look at switching to the DX3. Instead Spektrum has already manufactured a module set specifically for these radios which will give you DSM technology, but allow you to continue to use your existing radio and any features it may encompass.

    However, the average person will probably not even miss those features, as the radio itself is targeted towards the mid-level radio market. A prospective buyer will likely never have even used many of those features, so they won't even miss them. In addition, the fact that the features are slimmed down to just the ones that are of the most importance, can be a benefit. This is because you can get the radio setup in a few minutes instead of shifting through the manual trying to figure out settings that you may not have much of a grasp of, or even use once you figure them out. In fact, because I've used several JR radios myself, I found the DX3 easy enough to setup that I would have been fine to do so without the manual.


    The Spektrum DX3 is a radio like no other. It offers you the ability to eliminate frequency conflicts, and glitching, for a very reasonable price. At the moment no other radio merges these concepts together in this fashion although, over time, I'm sure many will try. I say this because I can see that, without a doubt, this is where the radio industry is headed to next.

    Initially, I wasn't a big fan of the gray radio with the bright orange buttons all over it. While I admit the technology behind the Spektrum had me extremely curious, I wasn't all that thrilled with the package they placed it in. However, I have to admit that my feelings have changed regarding this radio tremendously. After using it, the gray and orange theme has grown on me, and the radio fits my needs perfectly. I also feel it'll feed the needs of nearly everyone else, especially those who frequent the tracks.


    FMA Direct
    5716A Industry Lane
    Frederick, MD 21704 USA
    Phone: (800) 343-2934
    Fax: (301) 668-7619
    Website: www.fmadirect.com

    Duratrax
    Distributed Exclusively By
    Great Planes Model Distributors
    P.O. Box 9021
    Champaign, IL 61826-9021 USA
    Phone: (800) 637-7660
    Website: www.duratrax.com
    Products used: Evader ST Pro (Prebuilt)

    Novak Electronics, Inc.
    17032 Armstrong Avenue
    Irvine, California 92614 USA
    Phone: (949) 833-8873
    Fax: (949) 833-1631
    Website: www.teamnovak.com
    Products used: Super Rooster ESC

    Traxxas
    1100 Klein Road
    Plano, Texas 75074 USA
    Phone: (888) 872-9927
    Website: www.traxxas.com
    Products used: Revo

    Trinity Products, Inc.
    36 Meridian Road
    Edison, NJ 08820 USA
    Phone: (800) 848-9411
    Fax: (732) 635-1640
    Website: www.teamtrinity.com
    Products used: P-94 13x2

    Comments on RCU Review: Spektrum DX3 DSM

    There are no comments

    The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.

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