SSB installation question

[PaulJ]

I am installing an SSB in my steel boat. The installation instructions state that the case of the transceiver should be grounded…… but to what? Since it is a steel boat I have taken great care to isolate the electrical system from the hull and whilst I understand that the ATU has to be grounded to the hull to provide a counterpoise, I am a bit nervous about grounding the transceiver because as far as I can see, this will connect the negative side of the whole electrical system to the hull.

Would it be sufficient to ground the transceiver to the negative side of the boat’s electrical system which in turn is grounded to the engine but insulated from the hull ? On the other hand, if I have to ground the ATU anyway, does it make any difference if I also ground the transceiver ?

Would a practical solution be to put switches in the grounding straps and only make those connections when the SSB is in use so as not to provide a permanent route for any electrical “leaks”…..?


<hr width=100% size=1>I used to have an open mind but my brains kept falling out.....

 

[Gunfleet]

Hi Paul - different people will give you different answers and each set up will work in different ways. Some people (from the Antipodes?) have v strong feelings about how it should be done. However, my ssb works fine grounded to the sea via a 'porpoise' anode hung over the stern. This also grounds to the engine in the usual way (actually its real purpose) but is only in contact with the sea when I hang it over the stern. I don't have a steel boat but do have an aversion to holes in my boat, hence this arrangement.

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[Ships_Cat]

Hi Paul

I usually get jumped all over when I post install stuff for radios as it seems that it is an area where even the most inexperienced consider themselves experts so I normally don't bother competing. However, in this case you seem to know exactly what the isolation issues are with metal hulls so am happy to pass on what I do for them.

I do not earth the case/chassis of the radio itself, it invariably isn't important, so that gets rid of that issue (clearly earthing it is not a problem DC wise if your radio chassis is internally isolated from the DC negative as some are). Obviously the radio will ground to earth back through the transmission line coax braid and any shielding in the ATU control/power conductor to the ATU earth.

For the earth at the ATU to the hull one makes up a high value capacitor to go in it so that it offers low resistance to rf but blocks DC. The capacitor must be one that is non inductive, etc at radio frequencies so a large value electrolytic, for example, cannot be used. Do earth the ATU to the hull as it is the best earth possible on a sailboat.

I usually use around 10 off 0.15 microfarad monolithic capacitors in the ATU earth conductor to give an effective 1.5 microfarad capacitor (they will completely block DC but present virtually zero resistance to rf right down to the 2MHz marine band). You dont need special high voltage ones as the voltage across them will be very low due to the low resistance. The 10 or so of them is mainly to get the capacitance up and to provide sufficient current carrying capacity at rf.

To fit them I get a piece of unetched printed circuit board of sufficient size (it does not have to be very big as you will find the capacitors are very small) and cut a narrow strip out of the copper (say 3mm or so wide) right across the board to make a non conducting break so that each half of the copper side is insulated from the other side of the break. I then solder the capacitors across this.

The foil for your earth conductor from the ATU can then be soldered on one side of the copper and the conductor to continue to the earth attachment to the hull is soldered to the other side of the copper. This means you have the earth foil conductor from the ATU to the hull broken but connected together with the capacitors. If the earth conductor runs are only short, as they often can be on a metal boat (eg on my boat it is only about 300mm from the ATU earth connection and the hull grounding lug) I don't bother with copper foil and just use a heavy insulated earth wire. This means that one does not have to take any special precautions from it touching the hull and bypassing the capacitors as is possible with uninsulated foil.

Trust that solves your problem

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[ianabc]

Ah yes! Grounding on a steel boat !

At first I thought that a 2 wire system with single throw, double pole breakers connected to a positive and a negative bus bar in or behind the circuit breaker panel, would be best. I thought that ment NO connection to my steel hull.

Was I wrong...YES

The seperated positive and negative bus bars, double throw breakers are OK ( although now I realize that a regular circuit breaker panel would be fine IF all electrical conmnections are correctly polarised everywhere in the boat.

The ground in our boat is a enermous 316 stainless steel bolt welded to the hull below the nav. table.

I have been told by a relative who is an electrical engineer that there needs to be a connection to ground so if there is a short then there will be a circuit to trip the circuit breakers.

So the h/f ssb radio can be connected to the ground too...... for the counterpoise.

Let us know how you decide to do it!



<hr width=100% size=1>Building a steel sailboat in Comox, B.C. Canada.

 

[Ships_Cat]

<<<Some people (from the Antipodes?) have v strong feelings about how it should be done>>>

Have just read your post John. If I thought you knew the first thing about what you are talking about I would bite. However, as I know that you do not I need not bother explaining myself.

The poster appears to know exactly what the issues are and is unlikely to be led astray by garbage.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[BrianJ]

Re: Wish I

Yep.. wish I could contribute .. but I am also from " the Antipodes" ( john M).. however I dont know a bloody thing about the subject.. always have had a mate install my radio(s) ...and yes even on my steel yachts.... ><><><> reckon I would stick with ships_cat's advice though
BrianJ

<hr width=100% size=1>BrianJ

 

[PaulJ]

The Cat gets it....

Many thanks to all who have responded.

JohnM, your porpoise anode suggestion would probably solve the problem but is possibly not a very "elegant" solution. I would prefer something more permanent and wasn't even very keen on my own suggestion of putting switches in the grounding straps. The problems in metal boats are quite specific because of the problem of stray currents causing corrosion and eating away the hull.

Ian, I understand what your relative is suggesting. I am emphatically NOT an expert on any of this but I am very wary of providing a permanent path to the hull for any stray current. I don't know how or why but I'm afraid there will inevitably be the odd minor leak as time goes by. Grounding everything to the hull goes against everything I have read. My system is pretty much what you describe at the beginning of your reply.... The Battery negative and negative Bus are both connected to the engine. After emerging from the charging/switching/monitoring system (I have fitted an Adverc regulator) the positive cable wends its way through to the Circuit Breaker panel. I have then used over-sized, marine grade twin-core cable to each of the services. There is nowhere that it could short out to the hull...... I hope! Since the electrical installation is now virtually complete and the SSB is just about the last thing to be installed, I am very reluctant to change what I have already done.

Ships Cat, this would seem to be just what I was looking for. This is a simple and "elegant" solution that takes care of all my concerns.... I'm off to Maplins right now. Many thanks!

.....and thanks again to all who took the trouble to respond

Paul.

PS. I know some very nice Antipodeans......!



<hr width=100% size=1>I used to have an open mind but my brains kept falling out.....

 

[Gunfleet]

It works, That's all I claimed. Changing your name hasn't improved your manners, I notice. You're slipping back into old ways.

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[Ships_Cat]

Anything works John, it is only a matter of how well. On this topic I always give excellent advice and if I could not I would hold my tongue.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Ships_Cat]

Re: The Cat gets it....

Paul

I have had a nosey look at the Sailmail notes that Stingo refers you on the Liveaboard Forum to and in those there is a picture of what I describe. So if my description is not clear go to the Sailmail site, then menu>"Sailmail Primer">"Contents: Application Notes">"Grounding Tips" and right at the end of the article is a picture, only difference is they show the foil bolted to the PC board.

I should have mentioned that the total capacitance is not critical of course nor is the number, just near enough is ok. While the Sailmail article just refers to "ceramic capacitors" which includes disc ceramics of course, the capacitors they show in the photo are in fact monolithic ones as opposed to disc (monolithic are also ceramic).

You should expect good results if done properly. From my boat here in New Zealand I can work even mobile stations in the UK as long as propagation is at least average.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Talbot]

Dont really see how you have managed to ground to the engine, but avoid grounding to the shaft, propellor, cutlas bearing and - probably the hull

Unless you are using a rubber connector and ceramic bolts.

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[Ships_Cat]

Mark

Insulating shaft couplings between the gearbox coupling and the shaft are quite commonly used. They are usually, for yacht sized drives, a plastic disc that fits between the couplings and use various methods of avoiding the bolts shorting across (actually can't remember how our own is done but some have the bolts in bushes, some with the bolts alternatly staggered as one through the plastic, the next through the steel, etc). From memory there is one in the Vetus catalogue but a strange one I think it might be (haven't checked).

The following may be of interest, apologies if all known already -

Many marine diesels, including many Volvos for example, also have the sensors, alternator, starter, etc all with their negatives isolated from the engine as well, but if not it is, of course, relatively easy to insulate the engine from the beds (the flexible mounts for example). If an auxiliary alternator is put on they are also available with their chassis isolated from the negative (unlike automotive ones).

So in a boat it is easy to build it with the DC systems floating on a two wire system with the negative not grounded. This is normally the preferred method for custom boats of any construction but especially metal ones (it is dearer to do) but lessens the possibility of electrolytic problems. The yards I work with do the same up into superyacht size, for example one has a 65 m power yacht under way done the same.

Our own boat is steel and is done the same - the only things grounded to the hull is the ac earth and the ssb ATU earth (which is isolated for DC as explained in the previous post). The only anode on the boat is a teardrop one on one side of the fin keel - the shaft and prop are isolated from the engine and the hull (in our case we have metal bearings so the shaft and bearings run through a bronze tube inside the steel log - the tube is flanged at each end to the log but insulated from it with plastic spacers) and so need no anode (assuming correct materials are specified for the prop and shaft).

John

<hr width=100% size=1>I am the cat but I am only 6.<P ID="edit"><FONT SIZE=-1>Edited by Ships_Cat on 14/10/2004 11:58 (server time).</FONT></P>

 

[Roberto]

I suspect one can *build* an 12v system insulated from the hull, but with current use (meaning dust, dampness, bilge water or simply salt water entering the cooling water hose) I would not be surprised to find sooner or later some leaking currents a bit here and there
If one worries about corrosion, rather than trusting the fact of having an insulated hull I would advise fitting a leak current detector, imho



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[Ships_Cat]

Well in modern boats dampness is not a problem (for example the bilges will be dry) but as you say an earth leakage monitor is always fitted - manual push button lights glow equally type ones on smaller vessels and constantly monitored on larger ones.

If you have a damp boat it will be a problem to the DC isolated from the hull or not.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[peterbringloe]

Location of the tuner

I installed an Icom 710 in my steel boat and located the tuner inside the boat not far away from the base of the insulated backstay. I grounded both the tuner and tranceiver to the same place on the hull using braid. Performance was not great and not as good as others with GRP boats. In Washington I had a Pactor 111 modem installed for Sailmail and the SSB guru there blamed the poor performance on the location of the tuner. It shouldn't be inside the boat he said. So I made a box and relocated the tuner up on the arch under the radar. Used a 4 inch copper strip about 6 inches long to ground the tuner to the arch tube. The result was a spectacular improvement. Talked to Herb all the way back across the Atlantic and into the English Channel.

There are technical reasons for this that I'm sure the other guys who have replied will understand. But I think it's the same reason you should have stand-offs for your antenna cable going up the backstay.

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[tugboat]

You are obviously a very smart cat. /forums/images/icons/cool.gif I know sweet FA about this installation subject (though I used MF for donkeys years in the MN) and you've got my knackers in an uproar. I just purchased a steel boat this year which has an old Icom 600 fitted. The transceiver and antenna tuner are both earthed to the boat structure which is as per the instructions in the handbooks. I haven't tested the set yet and it is now all stripped out for a major refit period. I would obviously like the kit to work when I recommision the boat. Your answer is too complicated for me to deal with myself (I'm only a simple sailor after all) so do I need to get a professional in to do a major refurb of the system or might I have any expectation of the gear working as is. Can't ask the previous owner for feedback unfortunately. Thanks from tb. /forums/images/icons/frown.gif

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[Ships_Cat]

Re: Location of the tuner

The only likely issues that are different between inside or outside mounting of an ATU are:
- when inside mounting the section of the antenna from the antenna connection to the deck is inside the steel boat and so is shielded from radiating to the outside world. This should be kept as short as reasonably possible; say, less than 5-10% of the outside antenna length measured from the deck.
- the deck feedthough was done incorrectly, and possibly even coaxial cable was used (which it must not be).
- if the back stay is used as the main part of the antenna (remembering all of the wire from the top of the ATU forms part of the antenna) there was insufficient spacing between the antenna wire and the lower uninsulated portion of the back stay - should be four inches or preferably more to minimise coupling).

I personally would not put an ATU from one of the usual suppliers outside unless it was housed in something. SGC, while their ATU's are weatherproof, advise housing them. Icom say theirs can be mounted in the weather (they say "weather resistant"?), but again I would not but if one was it would be with modifications (such as removing the control cable pigtail on the AT-140; the AT-130 has no pigtail though).

You should get equal performance in a proper installation whether the ATU is inside the boat or outside. Inside the installation will be more reliable.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[PaulJ]

Re: Location of the tuner

Peter, thanks for that.... You've got me worried now because my tuner is also inside the hull, near the back of the boat and close to where the antenna feeder cable goes up through the deck..... That cable will run for about a meter under the deck before emerging through the deck right by the backstay, thence I was intending to tape it up the backstay to just above the bottom insulator. I think I will try this configuration first and if the performance is not good enough I will have to rethink along the lines you suggest.

Paul

<hr width=100% size=1>I used to have an open mind but my brains kept falling out.....

 

[Ships_Cat]

Re: Location of the tuner

Paul

If you tape it up the backstay you will have a definite problem with reduced performance and at worst insulation breakdown between the antenna wire from the ATU to above the backstay insulator resulting in arcing during transmit.

You have to use standoffs. You can get away with no standoffs with a fibreglass boat, providing the backstay chainplate is not earthed for lightning strike reasons, because the fibreglass is an insulator from ground at the bottom of the back stay - in fact on fibreglass boats you generally do not need a bottom insulator in the backstay providing the chainplate is not earthed.

Installation of the ATU inside the hull is no problem and is to be preferred (that is how almost all boats are done), but with a metal boat you need to ensure that the proportion of the total antenna length inside the boat is small. This is not normally a problem because the ATU can be mounted hard up under the deck and still have a short connection to earth on the earth side by grounding that to the steel hull close to the ATU. At worst you can epoxy a couple of strips of wood to the underside of the deck and screw the ATU to that.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[BrianJ]

Hey John ( JohnM) ..dunno what has upset you about Ships _Cat.... I find him full of information and always willing to advise...as indeed I find your postings interesting...
Now never having met either of you I have a respect for you both , but dont understand what John has done to upset you.... oh he can fight his own battles , but I find it unhealthy that two good posters should ,start picking on each other , for what I can see is no reason.
Oh sure I often have a go at the Poms and indeed the Kiwis... but all in good fun and I get back ( and expect it) as much as I give....
So how about the pair of you shaking hands over a " long distance beer" in the bar.
BrianJ

<hr width=100% size=1>BrianJ