Kenwood NXR-901 Service Manual page 89

900mhz digital base-repeater ocxo unit kxk-3 m3
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Adjustment for KXK-3 (M3) (OCXO unit)
We recommend that the frequency adjustment be checked each time the radio is serviced, or at least once per two years.
Maintenance should only be performed under normal temperatures.
■ Test Equipment Required for Alignment
Test Equipment
1. Frequency Counter
■ Adjustment Setup
The KXK-3 (M3) OCXO unit must be mounted on the NXR-901 repeater. Adjustment setup is shown as follows.
PC
Cross-wired
cable
To adjust the KXK-3 (M3) OCXO unit, some preparations are required.
1. The NXR-901 with the KXK-3 (M3) OCXO unit must be warmed up at least 72 hours before the adjustment is made.
The environment temperature must be stable.
2. The frequency counter (or reference oscillator) must be warmed up as defi ned by the equipment manufacturer.
■ Adjustment
Item
Condition
1. Setting
1) Connect the DC power output to the rear panel DC terminal (13.8V).
2) Connect the "REF OUT" terminal to the frequency counter.
3) Warm-up the equipment and KXK-3 (M3) properly.
4) Connect the front panel COM port (D-sub 9-pin connector) to the PC serial port with a cross-wired cable.
5) Activate the FPU to go to the test mode.
2. OCXO
frequency
adjustment
Note:
Adjusted data is stored in the KXK-3 (M3) internal memory, therefore no re-adjustment is required when the adjusted KXK-3 (M3)
is moved to another NXR-901.
ADJUSTMENT
Frequency Range
Resolution
Reference Frequency Accuracy
Input level
D-sub
NXR-901
REF OUT
9-pin
terminal
KXK-3 (M3)
DC power
supply
Measurement
Test-
Unit
equipment
f. counter
Rear
Major Specifi cations
Up to 50MHz
10 digits
Smaller than 0.0001ppm
Up to 5Vpp
Attenuator
Frequency
(if necessary)
counter
Adjustment
Terminal
Unit
Parts
REF
PC
OUT
ADJ
NXR-901
External
frequency
refernce
(if necessary)
Specifi cations /
Remarks
Method
±0.002ppm
9.99999998MHz~
10.00000002MHz
89

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