Furuno FS-1570 Service Manual page 46

Figure below shows the difference between AT-1560-25 and –15.
Dummy
Ω
(10 +250 pF:100 W)
Dummy board
(05P0543)
Fig.2.5.2 Antenna coupler, AT-1560-15 (For 150 W)
AT-1560-25: Leed relay used
2-21
2.5 Antenna coupler
COUP board
(05P0528)