TB7100 Service Manual General Information 81
© Tait Electronics Limited October 2005
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 heatsink when the transmitter is
or has been operating. Avoid RF burns. Do not
touch the antenna while the transmitter is operating.
Important The base station has been designed to operate with a 50Ω
termination impedance. 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 transmitter module, avoid overheating
during test transmissions. The heatsink must be secured to
the transmitter board. After completing any measurement
or test requiring activation of the transmitter, immediately
return the base station 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.
Important When the transmitter module is not connected to the
SI board, the transmitter will transmit continuously.
To overcome this, connect pins 1 and 13 of a 15-way
D-range plug and connect the plug to the auxiliary
connector of the transmitter module.
Note The frequency ranges 156.8MHz±375kHz, 243MHz±5kHz,
and 406.0 to 406.1MHz are reserved worldwide for use by distress
beacons. Do not program transmitters to operate in any of these
frequency bands.
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