New RF drain connections for marine electronics

[CMonster]

Hi.
We are just upgrading our marine electronics thanks to a lightning strike. We are going all Raymarine with a new SeaTalk NG backbone etc. According to the Raymarine forum we have to connect the RF drains to a bonding point :

'Should the vessel be equipped with a bonding plate and bonding cable, then the drain leads from marine electronics should be connected to the vessel's bonding cable'

Our bonding cable/plate is also the bonding system for the SSB and as far as we understood we should keep all radio stuff away from all marine electronic stuff to avoid interference

We have another bonding cable which is connected to the sacrificial anode, which is linked to the negative post of the batteries.

Which should we use, or should a different RF ground point just for marine electronics?

Thanks for your advice.

 

[William_H]

I am not so sure that grounding the electronics is so important. Usually this ground is achieved through the negative battery supply which in most cases is grounded to prop etc via the engine block. if you have an electrical system where negative is not grounded via prop etc then you might need a rethink. The bonding for anodes is connected to sea ground and in normal cases also the engine block and battery negative. Again check.
The bonding plate for the SSB is also connected to ground and battery negative. However capacitors can be used to isolate the plate for DC.
All this faffing around not connecting grounds to seawater ground is to avert or control electrolysis. So that may be your greatest concern.
As for connecting instrument ground to ships earth. I doubt it will cause interference however this should become obvious fairly easily if it does. A separate wire from instruments to ground as close as possible to the sea can avert sharing of a ground wire with sensitive electronics (SSB) as this sharing can induce interference. it is all a bit of a black art so just try and see. However the electrolysis problem is not so easily monitored. good luck olewill

 

[KellysEye]

THe SSB ground makes up half the aerial so the better it is the stronger the signal. We had a steel boat so the ground was attached to a metal strut holding the floor up. The other best ground is line the bilge with copper foil, then cover wih epoxy to water proof it. Otherwise connect it to any metal inside the boat, or fit a dynaplate plate on the hull, neither of those will be close to copper foil. The ATU should be connected with copper foil to the wire just before it goes through the deck or coachroof to the aerial on the backstay. When attaching a wire to copper foil bend the end of the foil into a V shape with the botton of the V turned back on itself to give a quadruple thickness, then use a bolt with a washer on side the wire is attached.