98-175666-A Appendix E: Grounding and RF protection E-5
Grounding Recommendations
To ground the BDU
The BDU should preferably be grounded with the short cable. Further, the BDU must be
grounded at its grounding stud to ensure a proper grounding if the short ADU cable is
disconnected.
The ground connection must be established at a dedicated RF ground (either capacitively or
electrically coupled).
The BDU provides galvanic isolation (as required) from its input power terminals to the
chassis/grounding stud. This way the isolated grounding arrangement is maintained.
To ground the ADU
If the mounting base of the ADU is electrically connected to the hull (or any other ground
potential than the BDU), the ADU must be isolated at its mounting bolts by means of
shoulder bushings and washers, see . This is done in order to prevent DC currents flowing in
the hull thus causing electrolytic corrosion.
However, a ground connection must be established via one of the mounting bolts using a
separate ground cable. The ground cable must be routed parallel and in close proximity to
the shielded coax cable hence connecting the ADU to the BDU Grounding kit. A heavy
gauge wire with tinned strands (min. 6 mm
2
) can be used for this purpose.
E.2.5 Alternative grounding for fiber glass hulls
To ground the BDU
The BDU should preferably be grounded with the short ADU cable and a grounding kit
(available from Cobham SATCOM). Further, the BDU must be grounded at its grounding
stud in order to ensure a proper grounding if the short ADU cable is disconnected.
Remember to make the ADU ground connection at the
same electrical ground potential as the BDU (see To
ground the ADU).
Figure E-4: Alternative grounding for aluminium hulls
Antenna
Terminal
Heavy Gauge Wire
RF Ground
(Capacitive OR
seperate ground plate)
-
+
Terminal Grounding Kit
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