SSB Ground Plane - connect to seacock?

demonboy

demonboy

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Sorry, sorry... yet another SSB grounding question!

So I've painted my 3m2 with my special copper paint (I haven't yet but pretend I have) and it's all under the water level. Is that enough for it to be 'touching' the sea to ground it or should I then connect my 3m2 ground directly to a sea-cock?

Also I have a sea-cock that is wired for ground already, presumably grounding all my other electronics. Could I attach it to this sea-cock or should the ground plane for the SSB be completely separate?

Thanks in advance!
 
You can connect to whatever you want cock!

Seriously, a ground plane acts as a reflecter to the antenna and is not to be confused with a ground. With a ground plane the transmitted energy is reflected up and propogates out of the antenna tip which is why it can get bloody hot if too much transmitting power is used for the size of antenna. All that power has to get out to carry your modulated signal so others can receive it, it doesn't just waft out like a summer breeze into the ether, it is aggressively forced out. If it can't get out you get melted sets in worst case.

A ground on the other hand is plainly an earth, I'm not sure why they ask for this as the sets all work perfectly well without it but I suspect the reason is to ground out any lightning strike. Years ago when using fixed base station FM sets on search and rescue work during a thunderstorm we disconnected all antennas from transmitter sets until the storm had passed. On the one occasion we failed to do so we had a strike which blew the set apart and caused no end of damage all around. Lightning would love an antenna and cause mayhem on a boat as the current rushed about trying to ground itself and frying everything in the process. Similarly with ali masts I suppose, sticking up in the air from an otherwise flat land(sea)scape is inviting the hand of fate in a thunderstorm.

If this supposition is correct and working on those lines, it would mean bonding the boat to seawater effectively to ground a strike and I seriouly doubt a seacock would be very effective any more than a chocolate teapot could hold hot tea!. A coil of copper wire of heavy gauge lying to hand to be lobbed overboard in case of an electrical storm would be a whole lot better, assuming one end was connected I mean, just guessing here.
 
This is a personal opinion, but I prefer not to have anything connected to my seacocks other than the hose. I'm of the 'unbond and isolate' school when it comes to this. I'd earth my electrics to the block.
As far as a ground plane is concerned I bonded my engine block and water tanks together with 3" copper foil and also bonded these to two strips of this foil running fore and aft on each side below water level. I didn't have a separate ground wire on the radio.
I assume you have done sufficient research to convince yourself that the copper paint will provide adequate mass to give a good ground plane - I haven't heard of this approach myself so can't comment.
 
I was advised that you need a large mass (engine block ,keel) for the Rf that is not transmitted to dissipate into.Failure to do that will mean overloading of the set.Copper paint doesn't qualify as a large mass .Not an expert,just passing on what I was told.
 
This thread seems to be wandering into the exotic regions of ground planes, aluminium foil stuck all over the coach roof under the antenna base and then painted over so long as it is connected to the antenna coax sheathing will work very nicely, not mass m'dear but area! Failing that, plate under the antenna although most have a base-loaded coil part of which is supposed to act as a ground plane.
 
OK, so as cliveshep has pointed out perhaps I am getting confused between a ground plane and a ground earth. I infer from your responses that no, the ground plane does not need to be touching something that is touching the water, it just has to be, as best as possible, below the water line. Some have argued that the ground plane doesn't have to be below the water line and that there are many examples of above-the-waterline ground planes working perfectly well. Whatever.

Moving on from this you mention connecting your water tanks, saltyjohn. I assume you are doing this because they are s/s? I have grp tanks so the only reason for me painting my tanks is because it is a nice big surface area, though three out of the four sides are 'inside' the boat. The sides touching the hull are, of course, inside the tank so it would be pointless painting them.

If everything gets really hot then would it be utterly stupid of me to use my diesel tanks as a ground plane?
 
You seem to be getting confused by what you have been told on different threads.

There are three Grounding?earthing points on your radio system.

1. The negative lead is connected to possibly your engine plus maybe looped to seacocks.

2. Groundplane?earth This is from the earth stud on the tuner and this can go to the groundplate on the cabin roof or your copper paint or copper sheet all over the bottom of the boat or the rigging or a groundplate .

3. The radio earth stud this may not be necessary however if it is then it can go to a sea cock not a plastic one or even a keel bolt.


All these earths are electrically disconnected from each other.
 
Yes, metal water tanks. What you are looking for is surface area close to the water or, better, in the water. An external ground plate is best, lead keel comes a close second then big metal structures like water tanks particularly if they follow the hull profile. About 30m of foil is good. The engine block is not so good because it is a bit 'knobbly', not much flat surface close to the water.
I used the advice of a man called Gordon West when I did mine - I think it was a magazine article. I don't know if he has written anything recently.
 
I wouldn't be painting the water tanks with my expensive copper paint - you want it to be as close to the water as possible, on the interior hull surface.
I suppose if you keep your tanks full at all times it would work!
 
The ground plane doesn't get hot, it is purely a reflector, it is the antenna tip that can get hot, and don't stand in front of it either when it's working as it radiates the transmitted energy.
 
[ QUOTE ]
you want it to be as close to the water as possible, on the interior hull surface.

[/ QUOTE ]

...and this is one of the problems. I can't find 3m2 of below the water line areas that are next to each other. I'm going to end up having a patch here and a patch there. I have been told I can connect these patches with a painted 80mm strip of copper paint, but it's all going to be a bit 'bitty'. I might have 1m2 in my aft cabin but with the diesel tanks between that area and the lazarette, where the ATU is installed, I'm going to end up painting the tanks as well. And then I have to somehow connect that through the lazarette bulkhead, so somehow I have to create a 80mm wide 'slot' to post some copper strip through to connect it all up.

A straight foward installation this ain't, but then it never is, is it?
 
In HF comms and I stand ready to be corrected, there are basically 2 antenna set ups a Di pole and a 'slopeing wire'
or 'end fed'. On most boats a di pole would make you look like a russian fishing trawler from the 70's and so for SSB an end fed is used together with a tuner, the ground plate is essentially the other 'pole' of the antenna.
 
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