Radio

Radio Frequencies

Radio frequencies are in heavy demand for many purposes. The spectrum of available frequencies is divvied up amongst the many user groups. In Australia, radio frequencies are controlled by the Australian Communications Authority. Use of radio frequencies by models such as the RC Laser is governed by the ‘Radio Communications (Radio Controlled Models) Class Licence 2002‘ of 7 February 2002.

Radio Control Models have been allocated frequencies in the 29MHz and 36 MHz bands.
The Class Licence rules mean that it is permissible to operate the models with no licence fee payable provided they operate on one of the permissible frequencies.
The allowable frequencies are:

  • 29 MHz Band : Greater than 29.72 MHz and not exceeding 30 MHz
  • 36 MHz Band : Greater than 36 Mhz and not exceeding 36.6 MHz and must comply with the formula; 35.990 + n(0.020)MHz; where n is a whole number that is at least 1 and not exceeding 30.
    ie. The allowable frequencies in the 36 MHz Band are;
    36.01; 36.03; 36.05; 36.07; 36.09; 36.11; 36.13; 36.15; 36.17; 36.19; 36.21; 3.23; 36.25; 36.27; 36.29; 36.31; 36.33; 36.35; 36.3; 36.39; 36.41; 36.43; 36.45; 36.47; 36.49; 36.51; 36.53; 36.55; 36.57; 36.59. (all MHz)

Note: Radio control model aircraft are also allowed to operate on these frequencies but they also have the intermediate frequencies in the 36MHz Band allocated for their exclusive use (ie. 36.02, 36.04, 36.06MHz etc). Obviously, a glitch in control in an airplane is far more catastrophic than in a boat or car and hence the exclusive frequencies for the fliers.
The radio system that you receive with your boat is already tuned to a band, and you cannot change that. But you can change the frequency within the band by changing the plug-in crystals.

Many believe that the radio is tuned to the crystal frequency and that if you change your frequency crystals very far from the one the radio came with, that the radio will not perform. The fact is the reduction in performance is less than 2% for the entire range of frequencies

Note: You cannot use a 29 MHz frequency crystal in a 36 MHz system and vice versa, even though the crystals look the same and fit perfectly.
For racing or sailing with friends you just need to check that there is no double-up of frequencies. If you do have a clash, as you will see below it is a straightforward job to change the crystals in your transmitter and receiver. It is always a good idea to have a spares on hand if you race or sail in groups.

Radio Crystals

The crystal is the heart of the frequency control program. This little quartz chip is what establishes the frequency in your system.

Crystals are little two-pronged plug-ins. They usually have a paper tag on them that tells both the Channel and the Frequency. There is one crystal for the transmitter and another for the receiver – they look exactly the same but they are not interchangeable.

The Transmitter crystal is marked TA, and the Receiver is marked RA. If the paper tag is missing, you may see an H in front of the TA, etc., printed on the metal crystal housing.

The transmitter crystal is usually mounted somewhere on the face of the transmitter, with a little plastic crystal holder that you just pull out with you fingernail. The receiver crystal is usually stuck into a slot in the side or end of the receiver.

Be very careful that the two prongs of the crystal actually go in the socket correctly. Sometimes they can be inadvertently wedged in beside the socket where they feel like they are properly installed but are not.
If you travel around and sail with different people a lot, it is wise to buy a second set of crystals for your radio system. That way, if you show up and someone is using your frequency, you can change your crystals and go sailing.
Crystals are fragile so don’t drop them or keep spares rattling around in a tool box. Wrap your spares in foam or cotton.

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