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Tuning Description
I
Required Test Instruments
Radio communication test set (HP8921)
10V/3A regulated DC power supply
Digital voltmeter
Ammeter
II
Preparation
Place the board to be tested on the test fixture (please ensure good connection between each test point
and the fixture), and connect the board to a power supply with DC voltage of 7.4V.
III Tuning Procedures
1. Description of Tuning Procedures:
1) Hold down PTT and SK1 for more than 2 seconds while powering on the radio. At this time, the LED
glows orange when the radio enters the Tuning Mode. After the keys are released, the radio will enter
the tuning item in this mode (the item depends on the position where the Channel Selector knob
locates). And LED will glow red or green according to the specific tuning item. Or
2) Connect a programming cable to the radio for real-time tuning in PC Programming Mode.
2. Description of Tuning Items:
Channel
Tuning Item
No.
1
TX Low Power
2
TX High Power
3
CDCSS Balance
4
CDCSS Deviation
5
CTCSS Deviation (67Hz)
6
CTCSS Deviation (151.4Hz)
7
CTCSS Deviation (254.1Hz)
8
TX Low Voltage Threshold
9
Max. TX Audio Deviation
10
SQL Normal Open
11
SQL Normal Close
12
RX Low Voltage Threshold
13
Bandpass Filter
Y indicates frequencies available for tuning, and the rest are blank channels without tuning items.
Note:
3. Specific Operations and Requirements:
1) Conventional Tuning Items (outside the tuning mode): TX Frequency Tolerance and VCO Lock
Voltage.
Note: CH1, CH2 and CH3 have been preset as low, medium and high frequencies respectively for wide
bands and CH4, CH5 and CH6 as low, medium and high frequencies respectively for narrow bands.
Make sure the antenna or load is connected before tuning.
1 set
1 set
1 set
1 set
Tunable Frequency
Wide Band
Low
Medium
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
72
TC-508 Service Manual
Narrow Band
High
Low
Medium
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
High
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
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