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220
Transmitter Fault Finding (25W)
TB7100 Service Manual
© Tait Electronics Limited
October 2005
Frequency Bands
Some fault-diagnosis tasks require programming the radio with the lowest,
centre or highest frequency in the radio’s frequency band. The relevant
frequencies for the different bands are listed in
. Note that the
following frequency ranges are reserved worldwide for use 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.
Can Removal
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 main-board assembly from the chassis.
In the case of the
PAD
TOP
and
PAF
TOP
cans, first detach the heat-transfer
block from the main board. Secure the block again after removing the cans.
Follow the procedures given in
“Disassembly and Reassembly” on page 99
Can Replacement
Replace all cans that have been removed only after repairing the board.
This applies to the B1, H5 and H6 bands. For certain other bands the
transmitter will not operate correctly unless all the cans are fitted.
Table 13.2
Lowest, centre and highest frequencies in MHz
Band
Lowest
frequency
Centre
frequency
Highest
frequency
B1
H5
H6
136
400
450
155
435
490
174
470
530
Содержание TB7100
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