It is sometimes suggested that opto-isolators should be fitted between the receiver and servos when long servo extension leads are used in large models or in gliders. This is supposed to prevent any RF injected into the long leads interfering with the operation of the receiver or servos (?) with an added advantage that a separate "servo only" battery could be used.

This is NEVER necessary and is NOT recommended with JR receivers and will often lead to unexpected side effects such as continuous servo chatter.

RF, injected into the low impedance output ports of the receiver, will be absorbed and cannot pass back through the receiver output stage to interfere with the operation of the receiver.

RF, injected into the servo due to the long leads, will always be present with or without an opto-isolator at the receiver end!

RF injected into the receiver battery lead is undesirable but the receiver battery lead must always be kept as short as possible to minimise the impedance and the battery lead does not pass through the opto-isolator anyway.

RF power reduces in proportion to the square of the distance and any RF injection problems will only be present at very close range. An example of this is blocking or swamping that is sometimes present on simple low cost receivers, where the receiver ceases to respond when the transmitter is very close to the receiver aerial. All JR receivers incorporate Anti Blocking circuitry (ABC&W) to reduce such effects to a minimum.

Regarding a separate battery supply for the servos, this is very desirable when many servos are used. It is best achieved by using a JR Multibox that not only allows a separate battery supply for the servos, but also enables up to four servos to be connected to a single receiver output port, each with its own travel, neutral offset and servo direction adjustment.

Before flying a model for the first time, it is sensible to check that all systems are fully functional under simulated flight conditions. For example, the take off and landing phases can be critical when flying a fixed wing model using many high power servos, especially if they are digital types. There will be a multitude of small inputs to all the flight controls as the pilot keeps the model straight & level during either the climb or descent. Flaps and retracts may be deployed in quick succession. All this intense activity will put severe demands on the battery/batteries, so it is vital to ensure that your power supply has a safe margin to power the receiver during the most hectic phases of flight. With the model being safely supported by helpers, preferably with the engine running (observing appropriate safety precautions), all the flight controls should be operated simultaneously, together with as many ancillary controls as possible. If there is even the smallest sign that the radio control system is not functioning correctly then it must be checked and the problem rectified before ground testing once again. The model should not be flown unless you have 100% confidence in the control system.

Of course, even with the best radio control installations, R/C systems can sometimes be affected by interference from external sources over which model pilots (and suppliers!) have no control. However, by taking sensible precautions, typified by those outlined above, the inherent risk in flying a radio controlled model aircraft can be kept to a minimum.

JR Multibox, available from your Model Shop, Order Code JRC99975, Retail Price £49.95.