104 General Information TM9100 Service Manual
© Tait Electronics Limited August 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 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 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 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 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 156.8MHz±375kHz,
243MHz±5kHz, and 406.0 to 406.1MHz are reserved world-
wide for use by distress beacons. Do not program transmitters
to operate in any of these frequency bands.
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