18INTRODUCTION AND MASTER TROUBLESHOOTING - Precautions b&ire Service
DOING SERVICE WORK IN GROUPS OF VO’bRMORE TECHNICIANS
.-I-7.IIf the service work is to be done by two or more technicians
working together, extra caution must be taken.
VoltagedistributionMaximum
voltage
NOTE ON INSTALLATION OF RADIO EQIJIPMEATeThe computers of the electronic control system has been
designed so that external radio waves will not interfere with
their operation.
However, if antenna or cable of amateur transceiver etc. is
routed near the computers, it may affect the operation of the
computers, even if the output of the transceiver is no more
than
25W.To protect each of the computers from interference by
transmitter (hum, transceiver, etc.), the following should be
observed.1. Install the antenna on the roof or rear bumper.
2.Because radio waves are emitted from the coaxial cable of
the antenna, keep it 200 mm (8 in.) away from the
computers and the wiring harness. If the cable must cross
hthe wiring harness, route it so that it runs at right angles to
the wiring harness.
3.The antenna and the cable should be well matched, and thestanding-wave ratio* should be kept low.
4.A transmitter having a large output should not be installed
in the vehicle.
5.After installation of transmitter, run the engine at idle, emit
radio waves from the transmitter and make sure that the
engine is not affected.
“STANDING-WAVE RATIO
If an antenna and a cable having different impedances are
connected, the input impedance Zi will vary in accordance with
the length of the cable and the frequency of the transmitter,
and the voltage distribution will also vary in accordance with
the location.
The ratio between this maximum voltage and minimum voltage
is called the standing-wave ratio. It can also be represented bythe ratio between the impedances of the antenna and the
cable.The amount of radio waves emitted from the cable increases
as the standing-wave ratio increases, and this increases the
possibility of the electronic components being adversely
affected.
