Regular readers will be aware that for the last 3 or 4 years the writer has been pushing the idea of using the microprocessor as a means of programming an R/C transmitter to suit more than one model. In a recent 'Hovering About' column I suggested that this should also include the ability to program rates, mixing, pitch curves, gyro gain, etc. along with the model changes.

While I am sure that I cannot claim all the credit, it is gratifying that JR have now produced an R/C outfit which will do all these things. Whats more, there are at least three other companies about to introduce equipment having very similar features. As far as the model R/C world is concerned this can only be regarded as "a giant leap for mankind".

Reactions to the JR system as observed at Sandown appeared to range from "fantastic" to "well, it's a bit complicated isn't it?" Certainly it is a little complicated, but this is inevitable with any equipment with such a range of options. Bear in mind too that the 'Apex' is a rather basic radio in its standard form. Presumably we can look forward to a 'computer' version of the 'PCM 9' in the near future!

The new 'Apex' is a full 8 channel system, can be programmed to suit seven (7) different models and is available in helicopter and aerobatic versions. At the moment of writing there is only one of each type in the country and the writer has only been able to examine the helicopter version so far - fortunately for a few days, otherwise this report would have been impossible. One useful feature which appears to be becoming standard on all new equipment - although until recently only available on Fleet equipment - is that it can operate in either PCM or PPM mode. This means that, while the new system uses the PCM mode, the transmitter can operate your existing JR FM receiver. Don't be misled by other reports which state that this feature is "switchable", however. It is in fact "programmable" - along with just about every other feature.

In simple terms this means that, apart from the trim levers, there are no adjustment potentiometers anywhere in the system - only switches. All other adjustments are made using a 16 character LCD display and a touch sensitive keyboard.

Lets start off by detailing the controls which are available. The transmitter case is the familiar 'Apex' article with the usual two sticks with trim levers. On the top left there are mounted the existing pitch trim lever (which doubles as Aux. 1 when the heli mode is not in use) and throttle hold switch plus dual rate/exponential switches for rudder and elevator.

The top right of the transmitter is a little more complex than the standard 'Apex' with a knob for Aux. 3, switches for Gear and Aux. 2, the dual rate/expo switch for ailerons and a three position switch labelled throttle/pitch curve. This switch selects between N (normal), 1 and 2. These latter two positions being effectively idle-up 1 and idle-up 2, although it should be noted that you could, in fact, set up the normal position to give idle-up if you wish.

Apart from the on/off switch and the plug-in RF module, these are the only controls fitted to the transmitter. Such features as reversing switches, end point adjustment, rates, mixing, etc. are set by means of the keyboard and display.

All of the advantages of this arrangement are not immediately obvious, but they are considerable. For instance, you can have exponential on either, or both, high and low rates (different amounts of expo too, if you want!), or you can program both of the rates selected by the rate switch - and you can set them to give more movement than usual!

In use it is first of all necessary to select a number from 1 to 7 for the particular model concerned and then set up all the various directions and amounts of throws, etc. for that particular model. At this point the choice also has to be made between PCM or PPM operation. Once this is done, it is only necessary to call up the particular model number to configure the transmitter to suit that model.

It is also possible to select normal or heli operation. In the normal mode the equipment becomes a normal eight channel system.

As with any specialised helicopter radio, the heart of the system lies in the various configurations of throttle and collective pitch which can be selected. In the case of the equipment being reviewed there are four different throttle/pitch combinations available :- hold, N, 1 and 2.

Throttle hold puts the throttle to a preset position and leaves the pitch channel under full control of the throttle stick. Pitch end points can be set and four intermediate points can also be programmed. These points can be anywhere on the pitch range so it is possible to have an 'S' shaped response if required. A neat touch is that if the throttle stick is inadvertently moved away from the idle position while the 'hold' switch is in use, the LCD display will prompt you to close the throttle and will ignore any attempt to switch of the hold until you have done so!

N, 1 and 2 allow full programming of the throttle and pitch channels with end points and four intermediate points being set individually on each channel. You can have idle-up (or even idle-down!) on all three if you wish. Curiously, unlike most comparable sets, there is no facility to change, or switch off, the tail compensation in the 2 position. Another curiosity is that there is a pitch trim control which remains effective on all of these modes and which operates over the full pitch range including changing the end points! There seems to be little point in retaining this feature of the original 'Apex'. A hovering trim facility would be much more useful.

Those of you who have followed the PCM saga to date should be aware that the JR system claims to be a 9 bit system unlike other manufacturers 8 bit systems. This means that the servos should move in 512 steps as opposed to 256 steps in other systems. It is rather strange that Futaba recently advertised the fact that the servos on their (8 bit) system moved in 512 steps while the programmable display on this new JR (9 bit?) system makes it plain that the servos move in 256 (0-255) steps! While your average modeller tries to digest that piece of information lets break the news to him that the normal servo travel is from steps 42 to 213 with the centre at 127 (nice round figures those).

This is so that the throw can be increased by 50% if necessary (127 to 213 = 100% - 127 to 255 = 150% - OK?). Those of you who believe some of the claims made in the past for servo performance and have a bent for mental arithmetic will have already worked out that servo resolution will be 90 degrees divided by 171 (213 minus 42) = half a degree. Or for 60 degrees servo movement = about a third of a degree - Hmmm.

By playing this numbers game you can set the end points of all 8 channels with more throw in one direction if you require. Interestingly, you can then alter this by setting the rates to a figure other than 100% - oh yes, the display refers to the rate settings in percentages. The throw set on the end point adjustment is referred to as 100% in each direction even if they are different, so remember it is a percentage of the end point setting - all clear! Both settings of the rate switch can be programmed to give from 0 to 150%.

If exponential is used, this too is set as a percentage, which is a little hard to visualise. Incidentally, when setting any switchable option the display will tell you which position the particular switch is in!

By now you will be wondering just how all of this is accomplished. The various options can be stepped through in sequence, rather like setting a wristwatch, or can be entered directly by keying in its particular number. The numbers are not consecutive so some form of 'crib sheet' will be needed for a while till you get used to it. In the case of the position numbers and percentage figures they are altered by means of two buttons which increment or decrement the figure set.

To show just how comprehensive the various functions are a full list is as follows :
Number - Function - Default position
11 - Reverse switches - Normal.
12 - Travel adjust - 42 to 213.
13 - Dual rate - 100%.
14 - Exponential - Linear.
15 - Sub trim - 0.
16 - Hold switch position - 42 & inhibit.
18 - Throttle curve - Linear.
31 - Elevator D/R switch - Separate.
47 - Revo gain - 0%.
48 - Acc gain - 0%.
55 - Mode select - Heli.
56 - Model select - As previously set.
68 - Pitch curve - Linear.
75 - Servo test 1.
76 - Servo test 2.
77 - Fail safe memory - Hold.
85 - PCM/PPM - PCM.
86 - Stopwatch - 0.00
87 - Alarm timer - 0.00
88 - Integrating timer - As previously set.

Function 15 allows the centre of each channel to be offset by up to 50% of the maximum throw.

Function 31 sets the elevator D/R rate switch to separate operation or commons it with the aileron D/R switch.

Function 75 moves all servos slowly from end to end over their full throw.

Function 76 moves each servo in turn from centre to full throw and back to centre in one direction and then repeats in the other direction.

All of these functions must be individually set for each model or they will assume the default setting.

The remainder of the system uses what appears to be the same receiver, battery pack and switch harness as used with the PCM 9 system and any of the range of JR servos can be used.

The competition modeller will probably use the system in a different way to that which is intended. For example model number 1 could set a model up for hovering manoeuvres while model number 2 changes things for aerobatics, etc. Note that this means that one model could be set up in seven different ways with no less than 28 different pitch/throttle combinations!

Just what the average modeller will make of the system is hard to say at this point in time. Whether he will use more than a fraction of the sets facilities remains to be seen. Like the PCM 9 system, one is left with the feeling that a little consultation with someone who actually flew models would not have been amiss. There is an impression that anything that the designer could think of was included for the hell of it. Nonetheless, it is an enormous step in the right direction and must set the standards for others to follow. Go to it!