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104 General Information TM9100 Service Manual

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.

Tait TM9100 Service Manual

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