Tx Gain Adjustment: R208 - Furuno FS-1575 Service Manual

Procedure)
1. Terminate the [J3: 36MHz WR2] on the TX board with a 50 ohm dummy load, and
then connect a frequency counter to each end of the dummy resistor. It is also
accepted to terminate the [J2: 36MHz WR1] instead of the [J3: 36MHz WR2].
2. Select [MENU] -> 9.SERVICE -> 3.RT SETUP -> 1.SETUP -> "REF OSC" ->
"0."
3. Make adjustment of "R143" so that frequency will come to "36 MHz + 1 Hz."
Reference)
Output power level at a 36 MHz frequency from [J3: 36MHz WR2] and [J2:
36MHz WR1] is 400 mVp-p with a 50 ohm load, and output power level at a
18 MHz frequency from [J1: 18MHz RX] is also 400 mVp-p.

2. TX GAIN adjustment: R208

Make MIC gain adjustment so that the FS-xx75T will output power of one-fourth of the
rated output power in the 12 MHz frequency range of SSB mode when the MIC input
level is "−46 dBm/600 ohms."
The rated output of microphone is "−36 dBm/600 ohms."
Rated output adjustment is made with the "R43" ALC variable resistor on the TX FIL
board.
Fig. 5.7.18 Relationship between ALC and TX GAIN
CONFIDENTIAL (internal use only)
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Power
TX GAIN ADJ.
5-47
ALC ADJ.
MIC Input
5.7 Board Adjustment