Furuno FS-1575 Service Manual page 309

Field Adjustment
When making field adjustment, if no AF GEN is available, it is acceptable to make TX
output power adjustment by selecting [MENU] -> 9.SERVICE -> 3.RT SETUP -> 4.TX
POWER (FREQ) -> TX TONE -> "1500 Hz".
Procedure)
1. Connect a power meter to the [T/R ANT] terminal of the FS-xx75T.
2. Select [MENU] -> 9.SERVICE -> 3.RT SETUP -> 4.TX POWER (FREQ) to open
the "TX POWER (FREQ)" window, and then make setting as shown below on this
window:
• TX MODE to "SSB"
• TX POWER to "HIGH"
• TX TONE to "1500Hz"
3. Press the PTT on the handset to transmit.
4. At this time, make adjustment of the "R43" ALC variable resistor on the TX FIL
board so that the output power of the FS-xx75 will come to the rated output power.
Reference)
Make ALC adjustment in the 12 MHz frequency range with low PA gain.
In frequency ranges with high PA gain, the ALC works to suppress the gain of IF
AMP on the TX board in order to maintain set TX output power.
Consequently, if TX output power adjustment is made through the adjustment of ALC,
TX output power will fluctuate in all frequency bands. It can be said that the ALC
adjustment is effective in making general adjustment of TX output power.
Furthermore, to make adjustment of TX output power in a specific frequency band,
select [MENU] -> 9.SERVICE -> 3.RT SETUP -> "TX POWER (FREQ)" or "TX
POWER (USER CH)."
IF TX
U6
(Variable Gain Amplifier)
Power Cont.
U2, 4
Power Cont.
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.
• TX FREQ to "12.5 MHz"
• TX POWER ADJ to "240" (Factory set)
TX
RF
DRV
2nd Lo
ALC
TX POWER
MOT
U14
ADC
T-CPU
Fig. 5.7.24 ALC Control Circuit Diagram
5-52
TX FIL
L1
PA
PA PA
B.P.F
x 8 Band
IN VR/VF
B.P.F
ALC
VS DET
PA-IF
5.7 Board Adjustment
T/R ANT
L18
OUT VR/VF
U1
ALC