Tx Board Adjustment: 05P0856 (Fs-1575, -2575, -5075); Mhz Ref Osc Frequency Offset Adjustment: R143 - Furuno FS-1575 Service Manual

5.7.3 TX Board Adjustment: 05P0856 (FS-1575, -2575, -5075)

J5: TX OUT

1. 36 MHz REF OSC frequency offset adjustment: R143

The 36 MHz REF OSC (reference oscillator) circuit is incorporated in the TX board and
the reference oscillating frequency is taken as the reference frequency for the PLL
circuit of TX, RX, WR1, and WR2.
"R143" is pre-adjusted by setting "REF OSC" to "0" so that the 36 MHz REF OSC
output frequency will come to "36 MHz ± 1 Hz." To make field adjustment of
frequency, select [MENU] -> 9.SERVICE -> 3.RT SETUP -> 1.SETUP -> "REF
OSC."
REF ADJ.
R143
REF OSC OFFSET ADJ.
CONFIDENTIAL (internal use only)
This confidential document is used only by FURUNO authorized persons.
It is strictly prohibited to reproduce the document in whole or in part without prior written permission of FURUNO.
nd
2 Lo
J3: 36 MHz WR2
Fig. 5.7.16 TX Board (05P0856)
36MHz + 0.4ppm/year
VCONT
Y2: 36MHz
U15
Fig. 5.7.17 REF OSC Block Diagram
5-46
J2: 36 MHz WR1
U17
U20
U19
J1
1/2
18MHz Rx
Q17
U18
Q18
Q16
5.7 Board Adjustment
R208:
TX GAIN ADJ.
Y2:
36 MHz Ref OSC
R143:
Ref OSC Offset ADJ.
J1: 18 MHz RX
REF PLL
J2
36MHz WR1
J3
36MHz WR2
1st Lo