Tait TM8100 mobiles Service Manual page 269

Emergency
Frequencies
Can Removal
Can Replacement
Transmit Tests
Secure the Board
TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
Table 11.2 Lowest, centre and highest frequencies in MHz
Lowest
Band
frequency
B1 136
G2 350
H5 400
H7 450
K5 762
The following frequency ranges are reserved worldwide for use as maritime
emergency frequencies or by distress beacons:
B1 band: 156.8MHz ± 375kHz
■
H5 band: 406.0 to 406.1MHz
■
Do not program the radio with any frequency in the above ranges.
There are five cans shielding the bulk of the transmitter circuitry:
■ PAD TOP
■
PAF TOP
■
DIRC TOP
■ PIN TOP
.
■
LPF TOP
To remove any can, first remove the board from the chassis. In the case of
the and
PAD TOP PAF TOP
main board. Secure the block again after removing the cans. Follow the
procedures given in "Disassembly and Reassembly" on page
Replace all cans that have been removed only after repairing the board.
An exception is the B1 band, however, where the
place if the transmitter is to operate correctly.
The following actions need to be taken when carrying out transmit tests:
secure the board
■
ensure the proper antenna load
■
limit the duration of transmit tests
■
protect against accidental transmissions
■
avoid thermal and RF burns.
■
These points are discussed in more detail in the following sections.
Before conducting any transmit tests, ensure that the board is adequately
secured in the chassis. This is essential if overheating of the radio is to be
avoided. (As mentioned earlier, the heat-transfer block must already be
secured to the main board of the assembly.) It is good practice to secure the
assembly by at least the two external screws and one of the internal screws.
The screws are labelled
need, however, to secure the lid of the radio body.
Centre
frequency
155
375
435
485
816
cans, first detach the heat-transfer block from the
I E
and in Figure 5.3 on page
Transmitter Fault Finding (>25W)
Highest
frequency
174
400
470
520
870
135.
can must be in
LPF TOP
139. There is no
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