Tait TM8000 Series Applications Manual

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Contents

Tait TM8000 Series Applications Manual Manual pdf 90 page image

90 Creating Your Own Options Board TM8000 3DK Hardware Developer’s Kit Application ManualSeptember 2003 © Tait Electronics Ltd4.1.3 Common Practices for Internal Options Board DesignThermalConsiderationsSelect components which withstand the temperatures inside the radio body,in particular during high duty cycles and high ambient temperatures.Tait recommends the use of industrial-grade components (<85°C).Heat dissipation added by an internal options board can reduce the radio’soperating temperature range or duty cycle. Keep heat dissipation to aminimum.Sealing The IP54 protection class no longer applies when the external optionsconnector or an additional connector are used. When fitting one of theseconnectors, it is the integrator’s sole responsibility to provide adequatesealing.ElectromagneticCompatibilityIt is important that the internal options board is electro-magneticallycompatible (EMC) with the radio itself and the external environment.This means that the internal options board is not affected by and does notinterfere with the radio or the external environment. An EMC problem hasthree components: a source, a coupling mechanism and a receiver.The coupling mechanism can be conducted and/or radiated.Key things to consider are as follows:Susceptibility toInterference If the internal options board has connections via the external optionsconnector and the radio’s antenna is located close to the options cable,significant RF pick up on to the cable may occur.If the internal options board contains sensitive analogue circuits (particularlymicrophone circuits), digital ground noise may be a problem if the internaloptions board is not earthed correctly.Electrostatic discharge (ESD) onto the options cable may cause damage tothe internal options board or malfunction if proper protection is notprovided.Emissions from theInternal OptionsBoardThe radio's receiver is extremely sensitive and radiation from the internaloptions board on the desired channel frequency may cause interference.If the internal options board has connections via the external optionsconnector and the radio’s antenna is located close to the cable, radiationfrom the cable may be picked by the antenna as interference.Radiation from the options cable, if strong enough, may interfere with otherdevices near the radio or cause failure to comply with EMC regulations inyour country or region. The cable creates a good antenna at highfrequencies.Follow the guidelines in “Guidelines for EMC Design” on page 91.