Author Topic: RF Ground (Read 7335 times)

Ziffius · « **on:** September 08 2016, 12:27 »

Hi, replacing my RM C70 with a RM A95 MFD chart plotter- going through all the wiring arrangements and spaghetti soup of cables trying to find if the boat has an RF ground point which is required for connecting up the power/data cable shield drain wire (if none the to battery negative terminal) anyone know if they have RF ground points on bavarias - BAV39 2005/6?? Also any electronics/electricians there - can the negative distribution bar behind panel 201 suffice to connect the drain wire to? Can't understand why drain wire is separate from the negative lead if you can connect it to the battery negative anyway- all a black art to me!

Lyra · « **Reply #1 on:** September 08 2016, 15:50 »

Shields are connected to earth (typically through the chasis of the instrument).
Normally boats do not come with a ground plane pre-installed.
I do not think that connecting to battery negative provides a good earth path because even if it is connected to the engine block, I believe the engine is isolated from the saildrive.
I think that running a wire to one of the keel bolts would be better as an earth point.

MarkTheBike · « **Reply #2 on:** September 08 2016, 20:59 »

Would the keel bolt be an effective earthing point if the keel is covered in antifoul? I've certainly got a separate earthing plate (not painted) added by the previous owner during commissioning if I remember the paperwork correctly.

Ziffius · « **Reply #3 on:** September 08 2016, 22:45 »

Going to see what happens tomorrow - I've soldered in the power wires and drain to the power and shield points on the original cable. Just getting my head round the seatalk to seatalkng interface. Then comes figuring the nmea183 connection.

patprice · « **Reply #4 on:** September 09 2016, 06:40 »

If using a keel bolt as an HF ground then I understand that link should be made so it cannot pass DC current and cause electrolysis.
I understand capacitors are used.
Not an expert here, other advise is welcome.

Lyra · « **Reply #5 on:** September 09 2016, 06:49 »

If it was understood that keel bolts can be used as a ground plane for HF then NO.
But as a path for shielding I believe it will be OK - I do not know what the resistance of antifouling is but the huge surface is definitely better than that oh the battery connection to the engine.
I also have a zinc attached to the keel so I know the electric path is good.

Salty · « **Reply #6 on:** September 09 2016, 09:12 »

I don't know if this would be relevant to your thinking, but considering that the mast is earthed directly to the keel such that in the event of a lightening strike there would be a safe path for the many thousands of volts to be earthed, would you also want your electronics connected to the same earth. My thoughts are that with umpteen thousand volts all struggling to make their way to earth, that they would take any path possible, including zapping their way through your valuable electronics. Maybe that would be the least of your worries at that time, but just a thought.

Nigel · « **Reply #7 on:** September 09 2016, 10:03 »

Quote from: Salty on September 09 2016, 09:12

... considering that the mast is earthed directly to the keel ... would you also want your electronics connected to the same earth...

I have little choice, the path goes via the antenna braid.

The Other Woman · « **Reply #8 on:** September 09 2016, 12:20 »

Hi Nigel

Is your antenna not fixed to a none conductive material (plastic bracket)?

Most are! $:-\$

Mick

Lyra · « **Reply #9 on:** September 09 2016, 15:06 »

If lightning strikes your mast you can take it almost for granted that your equipment will get damaged - the path through the keel is intended to protect as much as possible the boat and crew to minimize current though alternative paths.
BTW the conductor used is not really designed for this purposes as it is a "regular" earth cable. For lightning you prefer a conductor with large surface area over large crosscut (a flat braid as used sometimes in industrial distribution panels would be much better).

Ziffius · « **Reply #10 on:** September 09 2016, 17:52 »

Connecting ed as I said to the original c70 power cable and shield and after a bit of swapping the sea talk cables all is working - next is getting my head round the touch screen options with fat fingers

Impavidus · « **Reply #11 on:** September 09 2016, 18:31 »

Quote from: Ziffius on September 09 2016, 17:52

Connecting ed as I said to the original c70 power cable and shield and after a bit of swapping the sea talk cables all is working - next is getting my head round the touch screen options with fat fingers

dawntreader · « **Reply #12 on:** September 10 2016, 07:55 »

Quote from: Ziffius on September 08 2016, 12:27

Hi, replacing my RM C70 with a RM A95 MFD chart plotter.............................

I have been watching this post with interest as it is something I am considering too. Would it be too much to ask for a summary of your installation experience (with tips if any

). Also, how did you get on with the RADAR?

Thanks

Salty · « **Reply #13 on:** September 10 2016, 09:30 »

Quote from: Ziffius on September 09 2016, 17:52

................... - next is getting my head round the touch screen options with fat fingers

Be very careful when selecting things using the touch screen, it's very easy to make a wrong selection inadvertently.
The other day I was looking to change the language used from English(USA) to English(UK). At the time, while on the mooring, the weather was fooling around causing the boat to have a short bouncy movement which didn't really bother me except when I poked the screen menu, missed the target, and the language on show changed to something where I had no idea what it was saying, and could not go back because I didn't know what the hieroglyphics in that other language meant.
I already had a copy of the full instruction manual downloaded to my iPad, but this is written in a way that assumes the reader knows and understands the meaning of the options that the plotter is showing on screen. Unfortunately at this stage they didn't mean a thing to me. As a result I had to contact Raymarine who have provided a step by step, "poke the symbol second from the end on the right, then poke the third one down from the top on the next screen etc" to enable me to get back to English. I'll try it out midweek when I'm next onboard, but it's a total disaster at present. So I suggest you only alter settings when the boat is steady or with your hand braced to move exactly as the boat moves. Good luck.

Ziffius · « **Reply #14 on:** September 10 2016, 10:01 »

Wow salty I didn't see an English Uk option will go check - I appreciate what you say because I found it hard enough to select some things whilst stationary in the marina - definitely will avoid fiddling when not absolutely necessary.

Your post popped up as I was posting a long reply to dawntreader and it seemed to interrupt my upload so will try again.

Nigel · « **Reply #15 on:** September 10 2016, 13:57 »

Quote from: Ziffius on September 09 2016, 17:52

... next is getting my head round the touch screen options with fat fingers

If a user interface was ever designed not to be used on a boat, it's a touch screen. Just about usable in a hand-held device.

Ziffius · « **Reply #16 on:** September 10 2016, 14:08 »

Having trouble replying to dawntreader - will post couple of pics at a time as that may be the problem
Ok that seemed to work better than posting all pics at once.
The wiring pics are before the new plotter installed. The White Raymarine box is a 3 way junction on the seatalk linking the 3 instruments together - installed when AP fitted in 2013. I put in another junction - a D244 3 way junction between the tridata and the White junction box with an extra cable D230. The middle socket of the D244 was then connected to the seatalkng converter E22158 with the special spur cable supplied. The converter is connected to the A95 with the seatalkng cabled supplied.

The st60wind was originally connected to the other instruments via the White junction box and its other seatalk socket was jury rigged to the external gps and the C70. I initially used this cable into the E22158 converter but found I wasn't getting at least depth or external GPS info into the A95 hence the wiring arrangement above.

The power socket on the back of the C70 was unsoldered and sawn off - I should have done the same for the NMEA socket as well but didn't think to before flying to the boat. The A95 has a power/data cable plus video input lead. The power cables and drain were soldered to the back of the C70 socket so I could just plug the old power lead straight onto the new cable. Also on the p/d cable are loose cables for the NMEA connections - 2 ports. If I had brought the c70 socket I could have just plugged the NMEA cable straight into that and soldered the wires on (2 wires are for port 2 and aren't used so taped up)

The hole left by the C70 needed expanding vertically 172.6mm is the max height whilst width max is 233.1. I shaved top and bottom but in hindsight should have taken a bit more from top and less from bottom. The old fixing holes are covered by the A95 facia.

The old pathfinder radar is not useable with the new MFDs so I'll get a new quantum radar next year. The new radar only need power as it connects to the mfd via wifi. The adaptor that is mentioned in the quantum literature is only useable when you a replacing a digital radar - not the pathfinder. However there is already a nice fat cable running from the binnacle via the vicinity of the 201 panel up the inside of the mast so I will splice the power/Drain parts of that to the new radar as per this info from the Raymarine forum:

Welcome to the Raymarine Forum khusband,

It appears that you may not have completely understood the information or have been misinformed regarding the ability to adapt an analog radar cable for use with a Quantum radome. Should an analog radar cable presently be installed onboard the boat, then its plug may be removed and its power leads may then be connected to a switched 12 or 24VDC power circuit and vessel's bonding cable. The power leads located at the radome/open array pedestal end of an analog radar cable may then be spliced to the power and drain leads of power cable supplied with the Quantum radome. If not replacing the analog radar cable with a Digital Radar Cable, then communications between the MFD and radome would be exclusively via Wi-Fi. Whether communicating with a Quantum radom via Wi-Fi or via a Digital Radar Cable, the radar feature and performance should be identical.

Ziffius · « **Reply #17 on:** September 10 2016, 14:52 »

A clearer spaghetti bowl

Salty · « **Reply #18 on:** September 15 2016, 07:46 »

Going back to my comment in reply 13 above, Raymarines step by step guide worked a treat, and my touch screen plotter is now speaking English again 😊

dawntreader · « **Reply #19 on:** September 16 2016, 09:03 »

Quote from: Ziffius on September 10 2016, 14:08

Having trouble replying to dawntreader - will post couple of pics at a time as that may be the problem
Ok that seemed to work better than posting all pics at once..........

Thanks for the info