Having already covered a 'medium-tech' and a basic outfit in this series, it is now time to consider an outfit with all of the options that might be required by the dedicated contest flyer. This has involved a certain amount of soul searching as to how this type of equipment should be covered since a detailed examination of all the facilities provided - and their use - is outside of the scope of this magazine.

What we propose to do, therefore, is to give a general description of the equipment and a rough outline of what it is capable of, together with an assessment of the overall 'feel' of the system. Those who require a more detailed technical description should refer to the manufacturer or, where applicable, our sister magazine "RCM&E". The helicopter version of the equipment about to be described was, in fact, analysed in the January 1985 edition of that journal.

In common with most JR transmitters, the 'PCM 9' unit is based on an aluminium extrusion which forms the top, front and bottom of the case. In fact, this is different to the item used for the same manufacturers 'Apex' system and must, therefore, represent a considerable investment, in terms of tooling, to produce. The case sides are made of substantial plastic mouldings, while the rear is a separate aluminium sheet. Variations in the transmitter layout are catered for by numerous holes and cutouts in the main extrusion with the unwanted ones being covered by the label plates.

Two dual axis control sticks operate the four main channels in the conventional manner. Trim levers are separate and have a double action. If the levers are pulled outwards, extra travel is available beyond the normal trim range. This is useful for those occasions where extra trim is needed for that first flight and it is inconvenient to change the linkages.

Cutouts in the rear panel provide for the plug-in RF module and also allow access to the servo reversing switches, end point adjustments, etc. Servo reversing is available on all nine channels, while the total travel (end point) in each direction is adjustable on the first eight channels. Channel number 9 is the 'Gear' channel operated by a switch and is intended for the operation of retracting undercarriages. Normally, this utilises a set-up where precise adjustment of the end point is not required. Where this is needed, auxiliary channel 2 can be used.

The aerial is mounted inside the case and extends through the top panel which gives a very compact unit with the aerial retracted. Stick units feature ball-bearings and are very smooth in operation with no discernible free play. Lengths are adjustable over about 5/16 inch. A neck strap support is provided.

Despite the added complication of the PCM system, the receiver is of average size and includes the servo connectors in one end, as is now fairly standard. The latest receivers include a new type of circuit known as ABC&W which is claimed to give greater interference rejection.

JR manufacture a comprehensive range of servos, any of which may be used with the 'PCM 9'. Normally, either the low cost NE 505 type or the high power and high speed NE 4051 type will be supplied.

The standard battery pack is rather unusual in having a capacity of 700 mAH. This allows for the fact that most users of this type of system will probably be using more than four servos - and usually high power types too! The switch harness incorporates a charging lead which can also be used - with a suitable adaptor and connecting lead - to give direct servo operation from the transmitter without actually transmitting.

A dual output charger allows individual charging of transmitter or receiver if required. Separate LED's indicate that the appropriate output is functioning.

A feature of all equipment employing Pulse Code Modulation is the inclusion of a failsafe system, though it should be noted that PCM is not essential in order to provide this feature! This JR system was one of the first to house the various controls for the failsafe in the transmitter.

In operation there is a choice between the servos holding their last position or going to some predetermined point. If the latter is selected, you merely need to set the various controls in the position required and press the 'Fail safe memory' button on top of the transmitter. This system can then be deactivated to prevent accidental operation. When the equipment is switched on, it is necessary to press the 'Set/test' button, also on the transmitter top, to send the failsafe information to the receiver. If this is not done, the system defaults to the 'hold' mode. There is a 'monitor' lamp adjacent to the 'Set/test' button which flashes until the button is pressed to remind you of this requirement.

The above system is activated when the incoming information to the receiver is corrupted in any way. This includes interference, failure of the transmitter or any other loss of signal.

If the receiver battery falls below a preset point, this operates a separate circuit within the receiver which performs different functions in the 'aero' and 'heli' sets. In the aero equipment the throttle servo is moved to the half throttle position. If the throttle stick is then moved below the half throttle position, normal throttle action is then restored for 30 seconds. This process is repeated until the battery is exhausted.

In the 'heli' set the battery failsafe sets the throttle servo to a point selected by the 'idle up' control and leaves it there. In both cases, the other servos all function normally.

Aileron, elevator and rudder channels are fitted with dual rate/exponential switches. The dual rate can be adjusted between 40 and 100% of the maximum throw (remember that the maximum throw is also adjustable via the end point trimmers). The rudder dual rate can be set to operate automatically when the throttle is closed.

When the exponential option is selected, this is fully adjustable and can be switched out by the dual rate switch.

Various mixing options are available and can be used to give coupled flaps and elevators, coupled aileron and rudder and elevator trim correction when the flaps are lowered.

Additional facilities are included to cater for vee tails, elevons, flapperons and independently adjustable differential ailerons. As if that were not enough, any two channels can be mixed on a master/slave basis and there is also a throttle/pitch mixer with programmable delays for use with a variable pitch propeller. There is also a programmable snap roll button. You name it - it's there!

As with all helicopter R/C equipment, the main features all revolve around the various combinations of throttle and pitch coupling and mixing. All of the usual features are included such as 'throttle hold' and 'idle up'. In fact, there are two of each of these to cater for the differing requirements of practice and competition autorotations and various aerobatic manoeuvres. All of these options has its own individual adjustment for the lower end of the pitch range and there are separate trimmers for high and low pitch, together with 'hovering pitch' and 'hovering throttle' trims.

A conventional collective/tail rotor mixer is included with separate adjustments for ascending and descending tail correction. A switch on the front of the transmitter allows this to be easily switched in or out of circuit. That now comparatively rare item, an inverted flight switch, is also included complete with the vitally necessary 'inhibit' switch!

Dual rate/exponential switches are included on the three main channels in the same manner as the aero version. A useful additional feature is the provision for the aileron and elevator dual rates to be commoned onto one switch.

For those helicopters which utilise a moving swashplate to control the collective pitch a 'cyclic/collective pitch mixing' system is included. This allows three servos to be used to directly control the swashplate and move collectively or individually to control both cyclic and collective pitch. Note that this is not suitable for all helicopters - notably the Heim 'Star-Ranger'.

We have been using one of these systems in a helicopter for some time now and like the solid feel of the transmitter and smooth action of the ball-bearing sticks. Initially the preciseness of the control was a revelation and examination of the receiver output revealed this to be exceptionally stable. There is no trace of the delay in servo response which is characteristic of some PCM systems. Deliberate operation of the failsafe by switching off the transmitter when in the 'hold' mode causes the servos to 'freeze' without any unwanted twitches. When the signal is resumed, there is again no servo movement.

A set which will provide all that even the most demanding contest flyer will require, with a price to match. The only slight quibble is that a little more thought in the layout and operation of some of the minor controls would have been appreciated. In some situations there are several trim functions operating which duplicate each others actions. However, this is unlikely to cause any real problem to those who need all of the equipments facilities.