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