Handleiding Robbe Futaba FX-40 (pagina 101 van 105) (Engels)

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Tips and notes

FX-40

radio control system. Never power an ignition system from the

receiver battery; a separate battery is essential. Be sure to use

properly suppressed spark plugs, plug caps and shielded igni-

tion cables. Keep the receiving system as far away as possible

from any ignition system.

20.9 RANGE CHECKING

The new, ultra-fast PCM G3 system transmits fourteen chan-

nels at a r

esolution of 2048 steps, i.e. it transmits very lar

quantities of data in a short time. This is achieved by the use of

a special four-level FSK modulation process. A reasonably

high level of receiver signal is required if the system is to

decode it reliably at the receiver end. If the signal level is

inadequate or fluctuates - or even suffers interference - the

receiver attempts to regenerate the data signal. However, this

only works up to a particular threshold, after which it switches

automatically to hold-mode or fail-safe. The larger the quantity

of data a system transmits, the higher the signal level required

at the receiver. This is the simple - but not unexpected - fin-

ding from information technology research.

Poor servo lead deployment, or the use of particular brushless

speed controllers etc., may result in a reduction in the received

signal by up to 16 dB (a factor of 6), i.e. only 16% of the maxi-

mum signal strength is present at the receiver.

For models powered by jet engines (turbines) it is fundamen-

tally essential to connect the ECU via the robbe servo sup-

pressor filter, No. F 1413. Turbine ECUs generate such high

levels of interference that they may reduce effective range by

about 50% if no servo suppressor filter is fitted. The same filter

should also be used if a battery backer is installed in the

model, as the filters fitted to most battery backers are inade-

quate.

If any additional signal reduction occurs in flight, perhaps due

to changes in attitude of the model (aerial orientation) or other

sources of interference, brief ‘hold’ periods are the inevitable

result.

WE RECOMMEND THAT YOU CARRY OUT A RANGE-

CHECK BEFORE EACH SESSION WITH YOUR MODEL

We str

ongly advise that you make it a matter of routine to carry

out a range-check befor

e you operate any new model, and

whenever you have fitted a new receiver. Note that the model

should not rest on the ground for this; instead position it about

1 - 1.5 m above the ground. You can use a plastic or wooden

table as a support, with the model raised on it using a cardbo-

ard or wooden box. Never use a metal support such as a cam-

ping table. There should not be any conductive materials close

by (metal fences, cars etc.), and even your friends and assis-

tants should not be standing in the immediate vicinity.

• First switch the model on, but with the motor not running.

• Walk slowly away from the model, operating one control

surface slowly but constantly.

• While you move away from the model, watch the associa-

ted control surface and observe whether it deflects or stays

still. If possible, ask a friend to help you; he or she should

be able to see the model clearly, and observe the control

surface you are operating.

• As you increase ground range, rotate the transmitter to left

and right occasionally in order to simulate different aerial

positions relative to the model.

• To avoid ‘hold-mode moments’, the effective range of the

FX-40 under these conditions should be around 60 metres

with the transmitter aerial removed.

• If this part of the range check is successful, repeat it with

the motor running (caution: the model must be held secu-

rely for this test).

• The range you now obtain should only be slightly lower than

the previous figure (approx. 20%). If it is significantly redu-

ced, then the power system is causing interference to the

receiver. You should be able to minimise this effect by run-

ning through all the measures outlined above, and optimi-

sing them as far as the model allows.

20.10 SWITCH HARNESS

It must be possible to operate the receiving system switch

easily, without mechanical r

estriction, i.e. the cut-out in the

fuselage side must be large enough to avoid obstructing the

mechanism. In powered models with internal-combustion

engines, the switch should be mounted on the opposite side

to the exhaust, to avoid the danger of oil penetrating the hou-

sing and soiling the contacts. If your model is fitted with a

large number of high-power digital servos we recommend the

use of standard commercial dual-battery power supply sys-

tems.

20.11 INSTALLING SERVOS

When installing servos in a model, always use the rubber

ommets and brass eyelets supplied. When you fit the servo

retaining scr

ews, ensure that they are not tightened beyond

the point where the brass eyelets make contact top and bot-

tom; if the rubber grommets are compressed to this point,

their ability to absorb vibration is lost.

The following diagram shows two typical methods of moun-

ting servos.

Diagram “A” shows a wooden servo plate. Diagram “B” shows

the use of a plastic or aluminium plate.

In RC model cars the servos are usually fitted in the openings

provided for them in the RC installation plate. Robbe quick-

release servo mounts are a good choice for model boats. Ple-

ase take great care over mounting servos, as they are sensi-

tive to vibration.

20.12 SERVO TRAVELS / SERVO OUTPUT ARMS

Each servo must be able to move through its full arc of travel

without being mechanically obstructed by the contr

ol surface

or its linkage. This applies in particular to the carbur

ettor lin-

kage. The “full throttle” and “idle” settings must be determined

by the stick positions; never by the throttle’s mechanical end-

stop. If you ignore this warning, the servo motor will be under

almost full load constantly, and will consume an extremely

high current.

A range of servo output arms is available for robbe servos, and

they are illustrated in the picture on the next page. The dra-

wing also shows the angular change per spline segment.

Servos with splined output shafts permit fine mechanical

adjustment of the servo neutral position. The position is adjus-

ted by undoing the retaining screw and lifting off the output

device.

100

1Nut

2 Washer

3 Rubber grommet

4 Metal eyelet

5 Aluminium plate

6 Screw

1 Woodscrew

2 Washer

3 Rubber grommet

4 Metal eyelet

5 Wood

Robbe Futaba FX-40 Handleiding

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