JR DSX-9

JR DSX-9

The DSX-9’s build quality isn’t in doubt

I guess you could say Im a bit of a JR man on the quiet, although it hasnt always been that way. Over the years Ive owned various makes of radio, my first serious bit of kit being Futabas Field Force 7 Super. Remember it? I paid £395 for mine when it first came out – a significant amount of money back in the late 80s and one of the main reasons I treated the transmitter like a treasured family heirloom. I operated the set for 10 or 15 years before it was stolen, and I still miss it. Since then, a number of transmitters have passed through my hands yet, oddly, I feel most comfortable when Ive got my mitts wrapped around something from JR. Its hard for me to explain but whatever it is the company does with its design, ergonomic styling and choice of materials, I like. JR transmitters always have a dependable, solid feel, that I can only liken to the reassuring clunk of a Rolls Royce door. Yes folks, if transmitters were likened to cars, JRs output would be up there with the Mercs, BMWs and Range Rovers of this world. Hold a set when youre next visiting your local model shop and see if you dont agree.

So it was, then, that I felt entirely comfortable with this latest JR product, the new DSX9, dedicated 2.4GHz computer radio. In part, my comfort with the transmitter is due to it sharing the same case as my existing 35MHz JR PCM 9X, a set for which I have nothing but praise. Externally, then, the only real difference is the aerial, the PCM9s telescopic job having been replaced with the shortened 2.4GHz antenna with which were now familiar.
Whilst full range 2.4GHz radio has been around for about 18 months, I think its fair to say that as one of the worlds major R/C manufacturers, JRs venture into spread spectrum technology has been long awaited. Quite whether the company was caught with its trousers down when Spektrum launched its ground-breaking DX-7, or whether JRs hierarchy decided to take a measured approach with their response is not clear. However, respond they now have and, typically, the fruit of their labour looks very tasty indeed.

One point thats worth noting is the fact that this particular system has been delayed its official UK launch pending CE approval and the alterations that MacGregor Industries have had to implement in order to gain certification. Among the changes that make the transmitter legal in the UK are alterations to both its internal screening and power output. Its a detail thats worth bearing in mind before you consider buying abroad for as JRs sole UK distributor, only those bearing the MacGregor badge incorporate these changes and are approved for use in the United Kingdom.
QUALITY, AT A PRICE
Priced at a not insignificant £620.00 the DSX9 shares an identical specification to the £570 PCM9X II (the most recent version of the PCM9X) but is supplied only as a combo, i.e. with RD921 receiver, EA101 satellite receiver unit, 1500mAh NiMH Rx pack, heavy duty switch harness and instruction manual. Interestingly, the instruction manual is not dedicated to the DSX9, instead its a PCM9X II handbook, supplied with an eight page supplementary leaflet that simply explains the peculiarities of using a 2.4GHz system. In truth, its a bit of a feeble compromise when you consider the cost of the set, indeed, for my part, barely adequate is probably the only way to describe the 2.4GHz bit and, in truth, I think Im being kind! Why? Well, with respect to the 2.4 bit theres no description of what youve actually bought. Neither is there any mention of how best to install the two receiver units. I happen to know because I own a Spektrum DX7, but newcomers to the technology will not be aware. Accordingly, the second part of this article, incorporating our field test of the system, will explain exactly what to do. Until then, youd best take a look on the internet or contact JRs UK distributor MacGregor Industries.
Okay, thats my only real gripe out of the way, lets look a little closer at what weve got here.

Article continues below…

Enjoy more RCM&E reading in the monthly magazine.
Click here to subscribe & save.

SYSTEM WAR
For those who arent familiar with spread spectrum technology two alternative systems currently exist. JR and Spektrum are campaigning an offering thats designated DSM2, whilst Futaba has gone its own way with a solution labelled FASST. Reminiscent of the video format war between Betamax and VHS, JRs allegiance to the DSM2 system is an interesting development. What are the differences? Ultimately, it boils down to the way in which the transmitter and receiver communicate with each other. At switch on the DSM2 system scans the 2.4GHz band looking for an open frequency that it can use. Once found it repeats the process in search of a second, back-up, frequency which it also accommodates. Here, then, the model is protected by two signals; if one should be lost the second will guarantee a continuation of the flight as if nothing were wrong. Futabas FASST system is different in that it occupies an individual frequency for just two milliseconds, before moving on to another of the 80 channels that are available. Of course, in practical terms the end result is identical (glitch-free operation of your model and no chance of being shot down), so whos to say which is best?

The manual isn’t one of the DSX-9’s strong pointsIn common with the Spektrum solution JRs 2.4GHz radio employs a main receiver and a smaller remote receiver, the two connected via a 150mm extension lead. The theory here is that with the two located in a slightly different position in the model each will be exposed to its own RF environment, greatly improving the ability of the set-up to track the signal in all conditions. Moreover, on JRs RD921 Rx youll find a remote receiver socket on both sides of the case, thus allowing two remote units to be hooked up, facilitating even greater coverage of the RF environment. Modellers who campaign larger and faster aircraft will undoubtedly make more of this facility than your average Sunday flyer, but its there for all to use, and particularly useful if you seek some valuable peace of mind prior to letting your 1000-hour scale job slip the surly bonds of earth for the first time.

DSX IN DETAIL
As a third generation example of my faithful PCM9X the DSX9s menu layout, programming sequences and button presses are identical in every way, shape and form. For me, then, or anyone else who might be upgrading or converting from a PCM9X or 9X II, the system will feel as familiar as a comfy old pair of slippers. That said, anyone new to JR transmitters will quickly appreciate the intuitive menu layout and programming sequences, and with the back-up of the 180 page 9X II instruction manual youll soon be finding your way around the System and Function menus as if they were etched in your memory.

Well look at the programming options in more detail next month, however, skirting through the list its clear that the DSX9 is a very powerful beast. On offer are 9 channels, 30 model memories, advanced programming functions for fixed-wing (powered) aircraft, gliders and helicopters, mode interchangeable sticks, interchangeable switch functionality, and more mixes, gadgets and nifty gizmos than the average flyer can shake a stick at.
Since the X9 is such a complex box of tricks Im going to run through the content of the Function menus for the three model types (ACRO / GLID / HELI) in the next issue. For now well have to be content with a precis of the attributes that are common to all three, i.e. those located in the System menu.

The list is as follows:
Model Select: Used to switch between the 30 individual model memory settings.
Model Name: Allows each model to be given an individual eight digit name or number.
Type Select: Switches between the glider, fixed-wing (power) and helicopter menus.
Model Reset: Used to return an individual model memory setting back to the factory default.
Transfer: Used to copy the contents of a model memory to another DSX9 or PCM9X II.
Trim Step: Adjusts the sensitivity of the transmitters digital trim levers and switches.
Device Select: Offers the ability to alter the default switch assignments for GEAR, FLAP, AUX2, AUX3 and AUX4.
Wing Type: Allows the user to select one of three different configurations – NORMAL, FLAPERON and DELTA.
Swash Type: Used to select one of six (yes, six!) different swashplate control options.
Stick Mode: Offers the option of selecting from Mode 1, 2, 3 or 4.
Stick Direction: Sets the direction of the throttle stick for idle or, in glider mode, the direction of the spoiler stick.
BINDING & FAIL-SAFE
The primary advantage of 2.4GHz radio is the fact that the transmitter will only communicate with the receiver thats been attached to the current model memory. The process by which the transmitter and receiver are introduced (and married!) is called binding. Once bound its impossible for the transmitter to interfere with any receiver other than the one its been hitched up with. And herein lies the most significant advantage of 2.4GHz systems: no more frequency or shoot-down worries! Binding the transmitter to the receiver is a simple process that involves inserting the supplied bind plug into the charging lead of the switch harness, switching on the receiver and, finally, switching on the Tx whilst also pressing the bind button on the rear of the case. With this the transmitter will send its individual recognition code to the receiver and the jobs done.
Allied to the binding process is an area where the DSX9 differs from the PCM9X II, this being in the programming of the fail-safe function. Like a conventional 35MHz Tx, two fail-safe conditions are available: SmartSafe and Preset Fail-Safe. Basically these echo the traditional options, SmartSafe being the equivalent of a fail-safe hold function, whilst Preset Fail-Safe delivers the same result as the conventional user defined set-up. On loss of signal the first option allows all servos (except throttle) to hold their last position until a good signal is regained. Here only the throttle servo is driven to its preset fail-safe position, i.e. the position established during the binding process. Preset Fail-Safe differs in that, on loss of signal, all servos are driven to their preset fail-safe position – once again, established during the binding process. In truth its probably a slightly safer system than anything thats gone before as the throttle function has been separated from the fail-safe hold function. Of course, its still possible to make a mistake and set the throttle at half or full power during binding, but its far less likely.

Whole books have been published on the programming options and functionality of some computer radio sets, and in many cases theyve been written about transmitters which are far less capable than JRs new DSX9. Clearly, theres not the space in these few pages to detail the ins and outs of every option and facility available to X9 owners, however, what I hope to do here is give an idea of how very capable this system is, sufficient for you to decide whether or not its for you.

Article continues below…

Significant primarily for its use of 2.4GHz technology the DSX9 is identical to JRs current PCM9X II in almost every respect. In terms of its programming options, menu layouts, button presses and, indeed, appearance, this transmitter is, to all intents and purposes, a 9X II with a sawn-off aerial! Accordingly, we dedicated the first of these two articles (July 08) to providing an overview of the 2.4GHz system and introducing the main features of the set, finishing with a run-down of the System menu and the programming options available within. Here then, well expand a little on some of the more powerful options in the System menu, then dive into the nitty-gritty of the three Function menus that cater for the specific needs of fixed-wing power flyers (ACRO menu), glider pilots (GLID), and you helicopter chaps (HELI).

CLEVER STUFF
I think its fair to say that where high-end computer radios are concerned, 90% of us only ever use about 40 or 50% of our transmitters capability, and in many cases arent even aware of the functions that nestle within the chips and circuitry of our favourite set. Take a look at the DSX9s ACRO System menu, for example. I mean, did you realise that its possible to pre-program three individual flight modes each utilising its own set of mixes, control deflections, rate settings, exponential percentages and other variables? Each mode is selected using the three-position switch mounted on the top right shoulder of the Tx case and can be employed to, say, reduce your workload when landing. How? Well, at the flick of said switch you could effectively lower the wheels, deploy flaps to a set position (adding some elevator trim to counteract any pitch change), whilst also adjusting rates and expo to suit a lower airspeed. The possibilities are endless and particularly useful for competition pilots when, for example, theyre flying an aerobatic schedule that might require different trim settings for certain manoeuvres.

The flight mode facility is just one example of the DSX9s power and versatility but there are many more. Most people recognise the Wing Type function as being the way to select either a single servo aileron set-up, a two servo aileron (flaperon) configuration, or a delta mix. However, as far as the 9 is concerned, theres a good deal more to it than that. In addition to these more obvious options this is the function that allows you to operate, say, a four servo wing that uses one servo for each aileron and one for each flap. Its done using a feature called Dual Channels which instructs the transmitter to use one or more auxiliary channels as a second (slave) channel to the aileron, elevator, rudder and flap controls. Here, then, youre able to inhibit the use of a particular function switch (say, AUX4) and reassign it to flap duty where it can be configured (subjected to ATV, servo reverse, sub trim etc.) to operate in unison with the flap lever. Truth is, in this day and age where twin servo set-ups are common for aileron, elevator, flap and even rudder (Lancaster, B-25 etc.) it could almost be considered essential. Use it and youll never go back, particularly if youve fiddled and faffed with the Y-lead alternative in the past.
Incidentally, not only does the Wing Type function cater for V-tail configurations, it also sees to twin engine installations, providing a separate throttle channel for the second engine, complete with its own trim and throttle curves. Thats damn handy, too!

The screen is large and clearFUNCTION MENU
Common to all JR transmitters (and a few others), the Function menu holds the more obvious set-up tools, such as Dual Rate, Exponential and Travel Adjust. Since most will be familiar with the meaning and use of the basic options found here, Ill attempt to highlight one or two possible exceptions, starting with the throttle curve feature.
Whats that all about, then? Well, obvious though it may seem, an ideal throttle set-up provides a linear response in relation to the stick position, wherein a quarter of the stick movement provides a quarter of the engines available rpm – seems obvious doesnt it! Thats all well and good but, alas, your engine doesnt always see it that way. Instead, the carburettor set-up may cause the rpm to increase very rapidly from low throttle up to about half, then very slowly from half to full. Accordingly, when the throttle is open half way, your engine may in fact be running at 75 or even 90% of its maximum rpm. The throttle curve facility addresses all this by allowing the servo to move in an exponential fashion, i.e. through the manipulation of a seven-point curve. I have to be honest, its not something Ive ever used, although now its on offer I may just give it a try.

Ever wished you could slow the operating rate of those mechanical retract servos to make the action just a little more realistic? Thats exactly what the Servo Speed facility is designed to do and I intend to make full use of it in a Mk.9 Spitfire Im about to configure. Mind you, youll need to remember that in much the same way as the Travel Adjust feature is inoperative on dedicated retract servos, the servo slow function is similarly handicapped, so youll need to use regular high torque servos in this particular application.
On a similar theme I was equally impressed with the flap system delay facility. Here, where compensating elevator is mixed with flap, the DSX9 is able to coordinate flap deployment and elevator correction (whilst also reducing their relative speed), so that the two reach their predetermined positions at the same time. That really is pretty neat if you ask me and ought to make a tidy job of smoothing the transition from one trim state to the next.

Article continues below…

A GOOD MIX
Okay, hands up if youve ever used a programmable mixer in anger? Hmm, just as I suspected, not many! When you consider that a simple programmable mix can quite literally transform the performance of a model and make it much easier to fly, its a wonder we dont all use em. Suitably appointed with four switchable standard programmable mixers and two switchable multi-point versions the X9 packs the power to perform a variety of in-flight trimming operations. A standard mix, for example, might be used to prevent an aircraft pulling towards the canopy whilst flying a vertical down line with the engine at idle. To achieve the desired result the mix would be programmed to apply a set amount of down elevator at the point that the throttle stick is pulled right back and the engine is at tick-over. Of course, the ability to switch the mix in and out is essential to prevent any untoward pitch changes when landing. Not a problem for this transmitter.

As a further example, a multi-point (exponential) mix might be useful for eliminating pitch-coupling in knife-edge flight or, on a glider, to introduce elevator compensation whilst deploying spoilers. In the first scenario varying amounts of rudder input during knife-edge flight will require a greater or lesser degree of pitch (elevator) compensation. In other words the response needs to be a non linear one that necessitates the use of a customised curve. Similarly, when spoilers are deployed on a glider, the aircraft tends suffer a greater pitch reaction during the first 25% of spoiler activation, less so towards the end of its travel. Again, having the ability to tailor the compensating elevator response in proportion to the effect of the spoiler requires the programming of a non linear curve.

This pack should keep you in the air for plenty long enoughA CHOICE CUT!
Common to all model types is the Throttle Trim function that provides two alternative throttle cut options. The first allows you to use the trainer switch to kill the engine, whilst the second (Trim Select) allows the throttle trim to store the predetermined idle position. With this, the digital trim lever can be moved to close the throttle completely, after which just one upward click will return the trim to the aforementioned idle position. Personally, I prefer the trainer switch option although it should be noted that when youve got a buddy lead attached, the function is overridden. To stop the engine, then, youll need to land and disconnect the trainer lead before killing it.

THERES MORE…

It goes without saying that helicopter pilots are well catered for with the DSX9. Personally my heli skills are such that CCPM mixing, a few pitch and throttle curves, an idle-up function, throttle hold and gyro gain adjustment are more than enough to put a smile on my face. Fortunately, however, there are some wholl make far more use of the options available.

Article continues below…
A particularly neat feature of the Throttle Hold function, for example, is the throttle delay option which allows the speed of the throttle servo to be reduced when switching from throttle hold back to your regular flight mode. Ideal when practicing autorotations, and particularly when things go a little pear-shaped (as they often do!), it eliminates any sudden burst of throttle that you might get when the hold switch is released.
Many aerobatic and 3D helicopter pilots now use a throttle governor to help maintain a constant head speed throughout manoeuvres and, accordingly, the X9 allows you to set governor rpm values for each of the active flight modes. Here, then, the correct head speed is automatically selected when moving through each of the active modes.
As in the fixed-wing section, the selection of programmable mixers can be employed to correct tracking through aerobatic manoeuvres or to compensate for inaccuracies in the geometry of a mechanical cyclic / collective set-up. For example, should the helicopter move fore or aft when collective is applied, a programmable mix that introduces a corrective amount of elevator on application of pitch should sort things out.
Back in the System menu youll find six alternative swashplate mixing options that cater for regular mechanically mixed set-ups through two servo 180°, three servo 120°, three servo 140°, three servo 90° and four servo 90° CCPM configurations. Best of all, here, is the small on-screen representation of the swashplate highlighting which servo / swash linkage should be connected to which Rx socket. Very handy for those of us who get confused with such matters.

GLIDER GUIDER
So, what does the DSX9 have to offer glider fliers? In short, a veritable feast. Five flight modes are available with individual adjustment of most parameters, whilst the trim positions of each mode are stored and recalled upon activation. Ive already mentioned the benefits of the flap delay function in the ACRO menu, however in the glider section the feature is taken just one step further. Here, the Flight Mode Delay option allows a gradual and seamless transition between the various pre-set servo positions (flap, flaperon and elevator) of the five flight modes. An adjustable time delay of between 0 and 2 seconds is available and, Im told, is very pretty to watch. I can imagine playing with that for ages on the bench!

Little surprises seem to appear from every button press with this transmitter, a case in point being the Motor Hold option that allows the spoiler stick to be used for multiple functions. For example, in launch mode it can be used as a proportional throttle for an electric motor, whilst in, say, landing mode, throttle can be disabled allowing the same stick to double as a flap control.
Being the complicated beasts that they are to set up, I was quite encouraged to see a 26 page section of the manual dedicated to setting up a four function six-channel glider. Using three flight modes (launch, cruise and land) the step-by-step guide takes you through the set-up process from selecting a model memory to establishing corrective mixes in said modes. Its certainly the first place Id go if I had a glider to program.

Switch quality is goodRX INSTALLATION
Those who read part 1 of this report will recall a rather important omission from the instructions in the form of any reference to the installation of the two receivers (main and satellite). I understand the instructions are currently being amended accordingly, however, in the meantime it might be worth noting the following guidelines to ensure youre achieving the very best RF link possible.

Mount the main receiver as you would a 35MHz item. Wrap it in foam and secure it in a location that allows the two aerials to project at 90° to the main case.
The satellite receiver should be positioned as far as possible from the main unit with, ideally, its twin aerials running perpendicular to the plane in which the others lie.

In this respect, then, it would be ideal to have the main receiver aerials running in the span wise / fore and aft plane, with the satellite antenna running vertically from the top to the bottom of the fuselage.

TOP DRAWER
In the DSX9 I see a set thats aimed at pilots who enjoy maximising the performance of the aeroplanes they fly. Clearly, then, its not a transmitter thats going to leave many of us wanting. In offering such sophistication in conjunction with the unquestioned advantages in safety and reliability that weve come to appreciate of 2.4GHz systems, it really is a force to be reckoned with.

Subscribe & Save

Save £s and get RCM&E magazine delivered to your doorstep every month by subscribing to one of our amazing offers here.

Subscribe