The radio gear is the equipment that allows you to control your model. Radios are identified by two different things, Frequency and Channels.
Frequency - is the radio 'band' that the equipment operates on. In the UK a number of 'bands' have been allocated for the use of radio control equipment. The most common bands are 27Mhz, 35Mhz and 40Mhz. In the model boating world only two of these bands can be used, 27Mhz and 40Mhz. The 35Mhz band is restricted for aircraft only and it's use is prohibited at our, and most other, model boat clubs. Other frequencies are available, the latest is 2.4Ghz. In time, this could become the most popular as its specifications make certain problems associated with radio gear obsolete. All bands not reserved for aircraft use are referred to as 'surface frequencies' and can be used for boats, cars, tanks, etc. Also note, aircraft are not 'restricted' to using the 35Mhz band, they can use any of the other bands as well.
Channels - although this is a term that is also used when discussing frequency I am ignoring that for the moment. When talking about channels to identify a set we are talking about the number of different functions that a set can control. A two channel set can control two functions. This is enough for many model boats and works out as one channel for the motor and one channel for the rudder. Modern radio sets can have anyting from 2 to 12 channels and above. Generally, the more channels, the more expensive the set will be. Anything more than two channels is often referred to as 'multi channel'.
When purchasing radio equipment, you will see multi channel sets described as 'aircraft' or 'helicopter' sets. This does not mean they can't be used for boats, it means they have been developed with those uses in mind and will have functions that aircraft or helicopter modellers will find most useful. If the set you're looking at is on 27Mhz or 40Mhz it can be used for your model boat.
In order to choose the right radio set for your boat you will need to decide how many control functions (channels) you will need to control it. It is possible for one channel to control more than one item. E.g. one channel can control two motors or be used with switches to control many off/on functions such as lights, etc. If your boat has twin motors I find it best to use one channel for each motor. If your model has winches, a bow thruster, noise functions, etc you may wish to have each function on its own channel. As an example, my ferry, St Columba, uses five channels of a six channel set - one for each motor, one for stern rudder, one for bow rudder and bow thruster and one to operate the opening doors.
A radio set is made up of a number of components - transmitter, receiver, servos and batteries.
The transmitter - is the control box which you hold in your hands. It converts 'stick' movement into electrical signals and transmits those signals to the receiver.
The receiver - is the small device which you install in your model. It converts the signal from your transmitter into control pulses which are sent to the servos.
The servos - are the devices in the model which convert the signal pulses from the receiver into mechanical movement. Normally only one servo is connected to each channel and thence to one piece of equipment. When using electric motors to power your model, you will probably use ESC's to control the motors, these ESC's plug into the receiver in place of a servo.
Batteries - Many modern sets come with NiCad pack batteries for transmitter and receiver and also include a charger. When using ESC's it is often possible to disregard the receiver battery as most ESC's include a battery eliminator circuit (BEC) which will power the receiver from the main batteries. It is important to remember that, when using ESC's with BEC's, if you do not make use of the BEC function you should remove the red wire from the ESC's plug to prevent damage to batteries, BEC or receiver.
A two channel set (either on 27 or 40 Mhz) will be enough for most small boats but once you start to build bigger boats with twin motors, bow thrusters, lights, winches, etc, you will need to move to a multi channel set. As stated before the number of channels required depends on what you want to control. Most multi-channel sets are on 40Mhz, I don't think I've ever seen more than two channels on a 27Mhz set.
Crystals
All radio control bands are sub-divided into channels (this is the channel frequency, not the number of control channels). Crystals are used to setl the frequency that a set works on. There are 12 frequencies on the 27Mhz band and 34 on the 40Mhz band. Because of the larger number of channels available, 40Mhz is more popular than 27Mhz.
A new radio set will be supplied with a pair of crystals, one in the transmitter and one in the receiver. This 'pair' of crystals are not interchangeable, you cannot put the transmitter crystal into the receiver or vice-versa. Also, crystals designed for use on one band will not work on any other band, i.e. a 40Mhz crystal pair will not work in a 27Mhz set. Also, some manufaturer's crystals will not work in other manufacturer's equipment. For a list of crystal frequencies refer to the Hints & Tips - Frequency page. In the UK, 27Mhz crystals are identified by colours - 40Mhz crystals are identified by a three digit number which is the actual frequency the set works on. Your frequencu should be clearly displayed on your transmitter when in use.
Frequencies at the pond side are controlled by a 'Peg Board'. All frequencies are identified on the board, you put a Peg against the frequency you wish to use. If a Peg is already against that frequency it means that channel is in use and you MUST NOT turn on your transmitter. Doing so could cause another boater to lose control of his model with potentialy disasterous results. All model clubs operate some sort of frequency control.
Poor frequency discipline at the pond side can lead to unrest and arguments. ALWAYS follow the rules regarding frequency control before turning on your transmitter.
The new 2.4Ghz band does not use crystals to control frequency. The transmitter in these sets 'scan' the band and 'lock onto' a free channel. The receiver then scans for an IDENT from the transmitter to find the correct frequency and locks to it. This sytem means that frequencu control is not necessary as it is (supposedly) impossible for a transmitter to operate on a frequency that is already in use.
Computerised Radio Sets
Often referred to as 'Aircraft' sets, these sets use digital signal processing within the tramitter for greater accuracy. They also come with inbuilt, programmable functions often called 'mixes'. These 'mixes' are a way of 'mixing' the fuctions of two or more channels which are very useful for aircraft modellers. Even though these in-built functions aren't of a great deal of use to boaters, they can still be used. The most commonly used aircraft function would be the 'elevon' mix to 'mix' a twin motor boat's throttle so that one stick can be used to control forwards, reverse, left and right.
If you have a computerised set and want to use one of these mix functions I found it best to 'play' with it on the bench. Connect the servos, turn on the mix and see what happens!
Expandable Sets
Some radio sets can be bought with 'minimal' functions which can then be expanded in the future. The Robbe F14 Navy set is one of the best examples of this type of radio set. The plug-in modules are easy to install but, in my opinion, very expensive.
Modifying your set
I have made a modification to my 6 channel Futaba set for use with my ferry, St Columba. The model has twin motors running through two ESC's on two seperate channels. I wanted to be able to control the motors individaully when manouvering and together when 'sailing'. I made a modification so that, at the flick of a switch, I can go from 'single' stick throttle to 'dual' stick. If you are interested in details about this mod e-mail the webmaster.
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