TM8100 Mobile Radio Service Manual General Information 89
May 2004 © Tait Electronics Limited
Transmitter Issues The following issues relate to the operation of the transmitter:
■ RF and thermal burns
■ antenna loading
■ test transmissions
■ accidental transmissions
■ distress beacons
The precautions required in each case are given below.
Caution Avoid thermal burns. Do not touch the cooling
fins or underside of the radio body when the
transmitter is or has been operating. Avoid RF
burns. Do not touch the antenna while the trans-
mitter is operating.
Important The radio has been designed to operate with a 50 Ω
termination impedance, but will tolerate a wide range of
antenna loading conditions. Nevertheless, do not
operate the transmitter without a suitable load. Failure
to do so might result in damage to the power output
stage of the transmitter.
Important While servicing the main board, avoid overheating the
radio during test transmissions. The following is good
practice: Secure the main-board assembly in the chassis
with the two external screws and one of the internal
screws. The screws are labelled 9 and 11 in Figure 2.11.
The heat-transfer block must be secured to the main
board. The lid of the radio body may be left off. After
completing any measurement or test requiring
activation of the transmitter, immediately return the
radio to the receive mode.
Important Under certain circumstances the microprocessor can key
on the transmitter. Ensure that all instruments are
protected at all times from such accidental transmissions.
Note The frequency ranges 156.8 MHz ± 375 kHz,
243 MHz ± 5 kHz, and 406.0 to 406.1 MHz are reserved
worldwide for use by distress beacons. Do not program
transmitters to operate in any of these frequency bands.
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