The radio set

:  (R/C) set consists of a transmitter (the bit you hold) and in the model are a receiver, servo's and a battery. As you move the stick on the transmitter (Tx) it sends a signal to the receiver (Rx), which sends a signal to the servos, which then move the arm on top of the servo in response to you moving the TX stick. This arm is then connected to the control surfaces on the model via some sort of pushrod. Please see the pictures below The most popular manufacturers of radio control radios are Futaba, Spektrum, JR, Multiplex, Sanwa and Hitec. A 4 channel set will cost about £50, however if you can afford it you are much better off spending a bit more and getting a 6 or 12 channel set with mixers. Useful features include servo reverse and "rates". These make it easy to set up your model so that the controls work in the right direction. Another very useful feature is extra model memories. This enables you to easily use the same Tx with several models.
Modern computer radios can preform 100s of mixes and functions including talking to you

 

Important facts:

 R/C sets are available on 4 radio frequency "bands":

The newest is the 2.4Ghz band now used by most
 
The 35Mhz band - reserved for aircraft only still OK to use

The 40Mhz band - purely for ground based models, i.e. cars and boats, NOT airplanes or gliders.

And finally the 27Mhz band - for use by anyone, i.e. planes, boats, cars. The best choice  is a 2.4Ghz radio.

The main reason for this is that 2.4Ghz sets are pretty much interference free, because they work on a totally different principle to the other 3 types of sets. The 2.4Ghz radios frequency hop the 2.4Ghz band, meaning frequency clashes are impossible.

 Typical manufacturers include Spektrum, Futaba, JR, etc and the radios can easily be identified by a short aerial (approx 4" long)
Telemetry:> a  new concept, you can have flight information sent from your model to your TX screen, height battery voltage, speed, GPS and many more.
Flaps can be automatically lowered as flying speed is below certain speed, alarms can be set for low battery voltage