ssb ground plate

[john_morris_uk]

The principle of using radials is well established and easy to understand. There's certainly no need to buy into the OTT marketing hype of the KISS sellers. There's no secret to the design and no magic involved. If you want to go down that route, just get some lengths of wire or varying length (I can suggest some figures if you want?) and lay join them all together at one end and lay them all down in the bilge of the boat.

However all the KISS system and its adherents are doing is cashing in on the poor earth systems that many boats are hampered by.

A vertical antenna's performance is DIRECTLY proportional to the effectiveness of its earth system. (Can easily be shown mathematically if you are interested.) This means that no matter how good your ATU and your insulated backstay is then you won't get good results without an effective connection to the (electrical) ground round the antenna. The ideal would be for the vertical to be suspended over a silver (or silver plated-copper) solid plane of metal in all directions. If you have that in your mind, you can see what you are trying to achieve. All KISS system does is 'pretend' to be a ground for the ATU to work against.

The good news in all this is that sea-water is a relatively good conductor of radio frequency waves (compared to bare earth!) and so connecting to the sea by direct contact or capacitive coupling is the best bet.
The problem with capacitive coupling using foil is that the average hull thickness means you will have to have a VERY large area of foil to provide anything like a low enough capacitance. I suggest that one needs to achieve something like 0.1uf to not allow the capacitance to have too large an effect on the tuning of the system. As many will know, capacitance between parallel plates 'C' in a vacuum is given as:

C = ε₀εr(A/d) in Farads
ε₀ is 8.8542e-12 F/m
εr is dielectric constant (vacuum = 1)
A and d are area of plate in m² and separation in m

which means that the capacitance is directly proportional to plate separation. The dielectric of a GRP hull may give you a slightly better figure, but the average hull thickness means that even for ten square metres of plate perfectly stuck to the hull and if the separating GRP was only 2 cm then by my calculations the capacitance would only be in the region of 0.0443 uf and that is not a large enough capacitance. It 'might be' but it won't prevent unexpected results. Mesh will NOT work as well as the deciding factor is surface area. Short connections to major metal work in direct contact with the sea is the best bet. I am not convinced by the efficacy of the sintered plate, but some have found them to be very effective so don't throw it away if you've got one. (Or if you do throw it away, throw it in my direction so I can trial it!)

For those who say that they have seen a system working brilliantly with a few metres of foil and a mesh and a few connections, then I humbly suggest that what is happening is a mixture of coupling to the seawater, with a lot of the 'earth wiring and foil' being used as a counterpoise. The lengths of wire and size of foil will have occasional dramatic effects on the efficiency of the system and its no wonder that such a system sometimes works on some boats and doesn't on others. When such a system doesn't work very well on one frequency it might be perfectly ok on others. One some frequencies you will get interaction with the RF all over the boat and in unexpected places. Remember the BEST results will be from a short efficient connection to the sea. If that means copper tape to the keel plus foil on the hull under the aft bunks then go for it.

Finally, remember that even if you have a brilliantly set up system, with an excellent 'ground connection' on the ATU, but if you happen to transmit on a frequency where there is a resonant length of wire somewhere in the boats wiring set up, you WILL induce currents in that length of wire and get very strange effects round the boat. Just remember when you try to fathom out what is going on that RF is strange stuff and doesn't behave according to the laws of DC.

 

[Roberto]

Can you give me a few design details please.
. Is it as simple as a 1/4 wavelength wire for the mid point of both bands, strapped together and connected to the earth terminal of the ATU?

Yes, more or less.
One single radial per band might be ok, two *a lot* better, three usually not needed.. So if you use two bands, two radials for 40m and 2 for 80m should be enough. There is no need for them to be kept straight, they may well go up and down and be loosely coiled, especially the longer ones.
For more frequencies, I usually take two pieces of a 4- or 5-wire cable and cut the various wires to the correct lengths, connect all the 8 or 10 wires at one end to a square copper piece a few cm wide which is connected to the ATU ground lug. If you plan to use just two frequencies with two radials each then the 4 wires can be connected directly to the ATU.
Then -supposing the atu is located near the stern- one group of radials is laid to the port side, one to starboard. If possible they go forward through ceilings, etc, otherwise they are laid in the lockers, hidden away with a few plastic cable ties.

Then I check the SWR through all the frequencies likely to be used (this especially for people using both airmail and sailmail, which work on different frequencies), if there is a tuning difficulty on one particular frequency then I add one more specific radial, though usually when you have 4-5 radials at different lengths the ATU works satisfactorily in most bands.

If you awant to add other types RF grounds, like copper foil to the keel etc, they may well coexist with radials. I think you are aware of the possible implications when connecting some RF ground to other DC "grounds" as the engine, common ground point, 12v negative, etc... just be sure the type of connections you are adding are consistent and not disrupting what you already have onboard. The radials themselves are DC isolated from everything so they cause no problems.


As for the KISS working satisfactorily, it's not difficult to believe: this is a KISS ground having undergone surgery, I think the image speaks by itself

 

[john_morris_uk]

Might I humbly point out that 'coiling' radials actually alters the 'electrical length' of them (from the RF point of view). Also as the 80m amateur band has quarter wave length of about 66 feet, that is nearly twice round many sailing boats...

 

[coopec]

. Mesh will NOT work as well as the deciding factor is surface area. Short connections to major metal work in direct contact with the sea is the best bet.

John

Thank you for taking the time to make that extremely informative post. (I'm going to print it off for future reference)

So I take it that connecting the foil to the motor would comply with your suggestion "short connections to major metal work in direct contact with the sea is the best bet"

I am installing a lightning protection system but instead of having "grounding plates" I have 6 stainless steel 1.5M flat bars to dissipate the lightning charge. I understand that it is the edges (not the surface of the grounding plate) that dissipates the charge (hence the s/s flat bar which maximizes the amount of edge) If I connect the copper foil to a number of those "grounding plates" will that be adequate?

 

[john_morris_uk]

John

Thank you for taking the time to make that extremely informative post. (I'm going to print it off for future reference)

So I take it that connecting the foil to the motor would comply with your suggestion "short connections to major metal work in direct contact with the sea is the best bet"

I am installing a lightning protection system but instead of having "grounding plates" I have 6 stainless steel 1.5M flat bars to dissipate the lightning charge. I understand that it is the edges (not the surface of the grounding plate) that dissipates the charge (hence the s/s flat bar which maximizes the amount of edge) If I connect the copper foil to a number of those "grounding plates" will that be adequate?

Where are these 'bars' going to be fitted?

Lightening is a whole other area, and lightening protection (if I understand it at all) is about preventing the build up of the 'leaders' that you get before the actual lightening strike. Nothing is going to protect you against that actual strike, but the idea is to stop the strike happening in the first place.

My best advice is to try it and see. A general RF ground principle is 'as much surface contact as possible.'

 

[coopec]

Where are these 'bars' going to be fitted?


My best advice is to try it and see. A general RF ground principle is 'as much surface contact as possible.'

John

I have done a huge amount of reading and I am happy with what I am doing in regard to lightning.

The yacht is a ketch so I'll have
- Two strips (one strip under the main mast chain plates (P & S),

- Two starting directly under the main mast and going aft almost to the auxiliary motor. The main mast would be grounded to these strips which would then be grounded to the motor.

- Two strips under the mizzen mast chain-plates (these strips would then be grounded to the motor)

I'll have to ground the forestay (probably to ground-plate under the mast) but that will create a sharp bend at the bow roller and lightning doesn't like sharp bends ......

None of this is my idea. The authors of various articles are experts in the field of lightning but apparently lightning is unpredictable anyway

I take the threat of lightning very seriously as it is not unusual for ships to be struck, my TV aerial has been zapped (I'm right on the water), the fisherman neighbor has had his lobster boat damaged by lightning

 

[john_morris_uk]

John

I have done a huge amount of reading and I am happy with what I am doing in regard to lightning.

The yacht is a ketch so I'll have
- Two strips (one strip under the main mast chain plates (P & S),

- Two starting directly under the main mast and going aft almost to the auxiliary motor. The main mast would be grounded to these strips which would then be grounded to the motor.

- Two strips under the mizzen mast chain-plates (these strips would then be grounded to the motor)

I'll have to ground the forestay (probably to ground-plate under the mast) but that will create a sharp bend at the bow roller and lightning doesn't like sharp bends ......

None of this is my idea. The authors of various articles are experts in the field of lightning but apparently lightning is unpredictable anyway

I take the threat of lightning very seriously as it is not unusual for ships to be struck, my TV aerial has been zapped (I'm right on the water), the fisherman neighbor has had his lobster boat damaged by lightning

Sorry - not doubting your research about lightening for one moment and I was trying to imply that I wasn't an expert on that subject anyway.

I will reiterate my previous point which is that the best bet is to try it and see. I suspect that it might work very well. Don't worry about the whole rig being connected together. Rigging often ends up being grounded one way or another on many boats. (Although not as well as yours is.)

On our boat the mast is grounded with two heavyweight copper braid straps to the keel. Its the best we can do regarding lightening protection without adding fancy spikes to the top of the mast.

 

[coopec]

I will reiterate my previous point which is that the best bet is to try it and see. I suspect that it might work very well.

Thanks for your help.

My Father used to work with radio and he used to tell me as a kid that radio does not always work as expected and some things defy theory. You seem to be telling me the same thing.

Back in 1956 when TV was new to Australia my Father switched channels and picked up a channel broadcasting in the Eastern States a distance of 2000 miles (3200 km) away.

 

[MM5AHO]

I have done a lot of experimentation with my setup to see what works best.
I originally laid 5 ground plane counterpoise wires in the hull. Rivals have a thick hull, so I don't assume there's any capacitive coupling to the sea of much benefit.
The wires are standard domestic copper wire, several strands inside a plastic sheath. They are all connected to the ATU, which is located inside a stern locker, near the base of the backstay. They travel from there to the bow, one up the "spine" and the others either side spread apart.
I tried comparing this (by switching back and forth) with various connections to the sea. These included a pile of very wide braid with huge surface area, a long copper wire, a plate (copper, not sintered bronze), all suspected over the side into the sea.
There was nothing of these better than the counterpoises, though they all worked to a degree.
Ideally I'd like longer wires, but there's only so much hull to put them in!
It all works well on frequencies from 1.8 to 51MHz
Geoff

 

[KellysEye]

>Isn't the propeller like an external grounding plate so that if you connect your copper mesh/foil to the motor that is like connecting it to an external grounding plate?

The ground is a thin wire not Copper mesh/foil, Copper foil is use to connect the ATU to the aerial wire before the wire exits the boat. Our ground on a steel boat went from the radio with a small wire to a bolt on a steel strut that held the cabin sole up. If you touched the metal strut there was no evidence of any voltage or current, so using metal in the boat as a ground will not affect the prop or anything else.

 

[Birdseye]

The principle of using radials is well established and easy to understand. There's certainly no need to buy into the OTT marketing hype of the KISS sellers. There's no secret to the design and no magic involved. If you want to go down that route, just get some lengths of wire or varying length (I can suggest some figures if you want?) and lay join them all together at one end and lay them all down in the bilge of the boat.

However all the KISS system and its adherents are doing is cashing in on the poor earth systems that many boats are hampered by.

A vertical antenna's performance is DIRECTLY proportional to the effectiveness of its earth system. (Can easily be shown mathematically if you are interested.) This means that no matter how good your ATU and your insulated backstay is then you won't get good results without an effective connection to the (electrical) ground round the antenna. The ideal would be for the vertical to be suspended over a silver (or silver plated-copper) solid plane of metal in all directions. If you have that in your mind, you can see what you are trying to achieve. All KISS system does is 'pretend' to be a ground for the ATU to work against.

The good news in all this is that sea-water is a relatively good conductor of radio frequency waves (compared to bare earth!) and so connecting to the sea by direct contact or capacitive coupling is the best bet.
The problem with capacitive coupling using foil is that the average hull thickness means you will have to have a VERY large area of foil to provide anything like a low enough capacitance. I suggest that one needs to achieve something like 0.1uf to not allow the capacitance to have too large an effect on the tuning of the system. As many will know, capacitance between parallel plates 'C' in a vacuum is given as:

C = ε₀εr(A/d) in Farads
ε₀ is 8.8542e-12 F/m
εr is dielectric constant (vacuum = 1)
A and d are area of plate in m² and separation in m

which means that the capacitance is directly proportional to plate separation. The dielectric of a GRP hull may give you a slightly better figure, but the average hull thickness means that even for ten square metres of plate perfectly stuck to the hull and if the separating GRP was only 2 cm then by my calculations the capacitance would only be in the region of 0.0443 uf and that is not a large enough capacitance. It 'might be' but it won't prevent unexpected results. Mesh will NOT work as well as the deciding factor is surface area. Short connections to major metal work in direct contact with the sea is the best bet. I am not convinced by the efficacy of the sintered plate, but some have found them to be very effective so don't throw it away if you've got one. (Or if you do throw it away, throw it in my direction so I can trial it!)

For those who say that they have seen a system working brilliantly with a few metres of foil and a mesh and a few connections, then I humbly suggest that what is happening is a mixture of coupling to the seawater, with a lot of the 'earth wiring and foil' being used as a counterpoise. The lengths of wire and size of foil will have occasional dramatic effects on the efficiency of the system and its no wonder that such a system sometimes works on some boats and doesn't on others. When such a system doesn't work very well on one frequency it might be perfectly ok on others. One some frequencies you will get interaction with the RF all over the boat and in unexpected places. Remember the BEST results will be from a short efficient connection to the sea. If that means copper tape to the keel plus foil on the hull under the aft bunks then go for it.

Finally, remember that even if you have a brilliantly set up system, with an excellent 'ground connection' on the ATU, but if you happen to transmit on a frequency where there is a resonant length of wire somewhere in the boats wiring set up, you WILL induce currents in that length of wire and get very strange effects round the boat. Just remember when you try to fathom out what is going on that RF is strange stuff and doesn't behave according to the laws of DC.

Done some more reading since I started this thread John, and one item is the ICOM manual. This says that the ideal boat grounding is an encapsulated lead keel but that this should not be connected with round battery cable wire as I have done but with copper strip. two questions from what you have written above - the lead keel is coated with coppercoat, a mixture which I expect is non conducting. Is this likely to have any adverse effect? The second is what thickness copper strip? Can I use the relatively cheap adhesive strip used for guitar pick ups which I suspect is probably fractions of a tenth of a mm thick or should I use a more solid strip? Do I need to put a capacitative bridge in the strip to avoid stray dc current issues?

At the aerial end I am currently using old fashioned copper cored spark plug wire to connect to the backstay. This is multi strand totalling maybe 1 sq mm at best. OK?

 

[Gerry]

Fascinating stuff- but I, and I suspect many others, don't understand a word!
The KISS system cost $125, we plugged it in, running the cable under the deck in the aft cabin and, as if by magic, it just works....
And works REALLY well. We were replacing a copper grounding system that had been destroyed in a lightning attack-along with the radio and tuning unit. It has a far better range than the old system ever had.
I am sure that making your own is very feasible if you have the skills and it will be cheaper but for $125 it is an excellent solution for the technically challenged amongst us!

 

[ip485]

For the sake of repetition, having fitted the KISS system I cant imagine why anyone would fit anything else. I would have thought the pure simplicity would be enough, and then I doubt there would be much cost saving doing it any other way. More to the point it works perfectly, avoids the need for grounding plates the possibility of another point of corrosion.

 

[john_morris_uk]

Done some more reading since I started this thread John, and one item is the ICOM manual. This says that the ideal boat grounding is an encapsulated lead keel but that this should not be connected with round battery cable wire as I have done but with copper strip. two questions from what you have written above - the lead keel is coated with coppercoat, a mixture which I expect is non conducting. Is this likely to have any adverse effect? The second is what thickness copper strip? Can I use the relatively cheap adhesive strip used for guitar pick ups which I suspect is probably fractions of a tenth of a mm thick or should I use a more solid strip? Do I need to put a capacitative bridge in the strip to avoid stray dc current issues?

At the aerial end I am currently using old fashioned copper cored spark plug wire to connect to the backstay. This is multi strand totalling maybe 1 sq mm at best. OK?

The antenna connection sounds fine.

Edit: Forgot to say that the coppercoat paint layer will be very thin (relatively) so even if it insulates the keel from the sea electrically for much of the surface, the capacitive coupling will be high (small separation and large area makes for high capacitance and high coupling. Anyway, our keel is about to be coated with copper coat as well if that is any consolation.

The copper strip suggested by some places is 50mm wide by 0.6mm thick but the dimensions aren't critical at all. Substantial copper is the word.

 

[john_morris_uk]

For the sake of repetition, having fitted the KISS system I cant imagine why anyone would fit anything else. I would have thought the pure simplicity would be enough, and then I doubt there would be much cost saving doing it any other way. More to the point it works perfectly, avoids the need for grounding plates the possibility of another point of corrosion.

Would it possibly be because people don't like being conned into paying £130 odd for a few lengths of wire? I know it works, but I could have given you some suggested lengths of wire for you to make your own for a few pence.

Or alternatively do the job properly? The suggestions I make aren't hard to achieve and they should work EVEN BETTER than a few lengths of wire you buy expensively.

 

[ip485]

Would it possibly be because people don't like being conned into paying £130 odd for a few lengths of wire? I know it works, but I could have given you some suggested lengths of wire for you to make your own for a few pence.

Or alternatively do the job properly? The suggestions I make aren't hard to achieve and they should work EVEN BETTER than a few lengths of wire you buy expensively.

Point taken and well made.

My excuse is that it does seem a ready made solution that works. I wanted the icom tuner as near as possible to the backstay (because that was icoms recommendation) and since there is a large lazarette beneath wiring the kiss to the tuner and laying it out was a 5 minute job. Creating the wires, connectors etc and arranging them in a sheath without your technical knowledge would have been a much bigger job which was why the kiss seemed fair value for the price particularly as it proved far better than a gimmick and worked as well as i could have expected.