Furuno FAR-2107 Series Service Manual page 30

3. Adding shims to the RF unit
Insert one or two shims (0.8mm) as appropriate between the fixing rail for RF unit
and RF unit itself so that the gap between the RF waveguide and rotary joint is
0.1 mm to 0.5 mm.
Rail
Shim
RF unit
Rail
3
Gap
Rail
Shim