The process of interference suppression on a vehicle is aimed at reducing the amount of unwanted noise produced from the speakers of an ICE system. This, however, can be quite difficult. To aid the discussion, it is necessary first to understand the different types of interference.
Shows two signals, one clean and the other suffering from interference. The amount of interference can be stated as a signal-toniest ratio. This is the useful field strength compared with the interference field strength at the receiver. This should be as high as possible but a value in excess of or radio reception is accepted as a working figure. Interference is an electromagnetic compatibility (EMC) issue and further details can be found.
The interference field of the vehicle. For reception in the AM bands the aerial represents a capacitance of 80 pF with a shunt resistance of about 1 M. The set will often incorporate a trimmer to ensure the aerial is matched to the set. Contact resistance between all parts of the aerial should be less than 20 m . This is particularly important for the earth connection
Mobile communications
If the success of the cellular industry is any indication of how much use we can make of the telephone, the future promises an even greater expansion. Cellular technology started to become 414 Automobile electrical and electronic systems 10062-16.qxd 4/22/04 4:03 PM Page 414 Comfort and safety 415 useful in the 1980s and has continued to develop from then – very quickly! The need and desire we perceive to keep in touch with each other is so great that an increasing number of business people now have up to five telephone numbers: home, office, pager, fax and celluar.
But within the foreseeable future, high-tech digital radio technology and sophisticated telecommunications systems will enable all communications to be processed through a single number. With personal numbering, a person carrying a pocket-size phone will need only one phone number. Instead of people calling places, people will call people – we will not be tied to any particular place. Personal numbering will make business people more productive because they will be able to reach, and be reached by, colleagues and clients, anywhere and anytime, indoors or outdoors.
When travelling from home to office or from one meeting to the next, it will be possible to communicate with anyone, whenever the need arises. But where does this leave communication systems relating to the vehicle It is my opinion that ‘in-vehicle’ communication equipment for normal business and personal use will be by the simple pocket sized mobile phone and that there is no further market for the car telephone. Hands-free conversions will still be important.
CB radios and short-range two-way systems such as used by taxi firms and service industries will still have a place for the time being. However, even these may decline as the cellular network becomes cheaper and more convenient to use.
Last word
A revolution in the use of information technology in vehicles is taking place! Advanced computing, communications and positioning developments are being introduced in even the most basic vehicles. shows an Auto PC/Car Multimedia system. However, there were several barriers to the widespread use of such new technology.
