Best way to connect SSB ground plane sections

[demonboy]

Hello,

Yet another SSB ground plane question but a simple one really. I'm having to connect up different sections of the boat's hull/floor to get my 3m2 ground plane. This means connecting sections via bulk heads and through doors (from the heads to the cabin, for example).

Assuming I use some 80mm wide copper strip to connect two sections, how should I connect those copper strips? Imagine, for example, two sections are divided by a cabin door. I can't run the copper strip up over the curvature of the door frame cos that would look unsightly and is impractical. Instead I guess I should run the copper plate up the vertical of each floor section and then drill through the door frame and bolt through something to connect those two bits of copper strip.

Am I on the right lines? What should I use to bolt and connect those two strips with?

Any help appreciated, thanks.

 

[Fr J Hackett]

Faced with the same problem I cut a slots using a jig saw that I could thread the foil through under the cabin sole and through various lockers. I soldered the strips together using lots of flux, solder and a small gas torch. The foil can then be folded against frames and bulkheads out of sight and painted with the slots sealed, I used Sikaflex but you coul use resin as well to seal the slots and bond the strip to the various surfaces that it passes over.

 

[MM5AHO]

I ran single wires from a common point at the ATU (stern) round the hull spread apart, and as far forward as I could (2 to bow). These 6 wires work well. Longest about 8m.

 

[demonboy]

Geoff, what type of wires did you use?

 

[pmyatt]

I ran single wires from a common point at the ATU (stern) round the hull spread apart, and as far forward as I could (2 to bow). These 6 wires work well. Longest about 8m.

Would be interested in more detail regarding using wires as a ground plane - am about to install an ICOM M801E and have been advised that copper ribbon and one/two dynaplates is the only correct way.

 

[john_morris_uk]

Would be interested in more detail regarding using wires as a ground plane - am about to install an ICOM M801E and have been advised that copper ribbon and one/two dynaplates is the only correct way.

Copper/ribbon and dynaplates are certainly better than running wires (in antenna terms 'counterpoises' around your boat.

Try using a bronze bolt or stud through the bulkhead and bolt the copper ribbon to it either side?

(You can use thick wide tinned copper braid rather than copper strip if you can find any.)

 

[whipper_snapper]

Would be interested in more detail regarding using wires as a ground plane - am about to install an ICOM M801E and have been advised that copper ribbon and one/two dynaplates is the only correct way.

I am reluctant to get into another HF grounding discussion...but...wires can provide the counterpoise needed but they work in a different way to a ground plate. But to add complication, when they are run along a hull they act as a mix between the two alternatives because they also link to the sea pretty effectively through the hull. In principle however, if they were acting as pure counterrpoises, they would need to be tuned, so most people have several cut to different lengths for different frequencies. The big difference is that used in that way any normal thin wire works perfectly well.

Not sure if that helps! I guess the basic message is that several tuned wires as counterpoises can work very well indeed, but will tend to work a lot better at some frequencies than at others.

Finally, I would add, that dynaplates certainly work, but on most boats there are cheaper and better alternatives. I do however use a pair of dynaplates because I have zero immersed metal on wooden cat.

 

[Cliveshep]

You might find some very useful information here: http://www.seacom.co.uk/#aerials

or here:
http://members.toast.net/boatguy/vhfant.htm

or a low VSWR antenna requiring no ground plane here:
http://www.saltyjohn.co.uk/metzmantavhfantennaaerial.htm

 

[Bilgediver]

Copper/ribbon and dynaplates are certainly better than running wires (in antenna terms 'counterpoises' around your boat.

Try using a bronze bolt or stud through the bulkhead and bolt the copper ribbon to it either side?

(You can use thick wide tinned copper braid rather than copper strip if you can find any.)

The bolts alone will defeat the purpose of using braid as for RF it is surface area that counts. If you are pedantic then get some braid and thrread through the bulkheads and then fan out the ends where you solder to the copper ribbon.

Even copper tube is better than bolts!!!!

 

[john_morris_uk]

The bolts alone will defeat the purpose of using braid as for RF it is surface area that counts. If you are pedantic then get some braid and thrread through the bulkheads and then fan out the ends where you solder to the copper ribbon.

Even copper tube is better than bolts!!!!

With respect - I was an RF engineer in a previous career and although you are right when you say that RF tends to use the surface, what do you think happens when the braid or copper tape meets the bolt on the inside of the hull where the dynaplate is bolted?

Furthermore - skin effect is more pronounced at higher frequencies - its why we always used to silver plate uhf and shf and microwave rf items...

 

[Beadle]

Not quite sure what you mean by tube being better than bolts.

As with many other things you can get into a diminishing returns situation with earthing.

A Dynaplate gives a large surface area in contact with the sea - or perhaps a large area capacitor plate when the surface has corroded.

Certainly better than random lengths of wire which may or may not act as counterpoises or as capacitors depending on frequency. There is a further disadvantage that should it be a true counterpoise the distant end will have a very high voltage on it which is not a good thing.

The downside of Dynaplate of course is the cost. For a cheaper alternative perhaps the greatest area of copper foil that is manageable stuck to the inside of the hull would have high enough value of capacitance to serve as an acceptable earth.

Not as good as Dynaplate perhaps but for normal use I would suggest adaquate. And no bolts through the hull.

You could always have it silver plated like JM's aerials although I doubt HMG would pay .... ..

 

[john_morris_uk]

I am also skeptical of the 'capacitive coupling' achieved by various lengths of wire arranged inside the hull. As most hulls grp thickness is measured in mm which makes the spacing between the wire and the conductive sea rather large and the capacitance is proportional to surface area, I suspect that the actual value of capacitance achieved is fairly small. If I have a minute I will try and estimate a value and see whether the effect is worthwhile at the frequencies involved.

 

[MM5AHO]

Re wires and capacitance.
Its correct that capacitance is dependent on surface area, and also seperation between the wires and the sea (hull thickness), so maybe I don't have much capacitance.

What I do have is a system that works. And thats what counts eventually.
My wires are not quite random, they are set for the amateur bands, which is what I use the HF for. My system works best on the high bands, as might be expected, but is quite good round the UK and Eu on 80m and 40m bands.

 

[mdrifter]

No DynaPlate...

On our first installation I used 2 dynaplates connected together by 3" copper "tape" - passed through various bulkheads using bolts and 1" washers; tied in ss fuel tank and engine block. It worked Ok in conjunction with M710 & SGC230. On second installation I did away with the DynaPlates altogether. Used copper tape, bolts & washers as before and tied in ss water tank and engine block. I was going to tie in keel bolt but haven't done so, yet...Same M710 & SGC230. Appears to work quite well with wl2k @ c.30W RF, insulated backstay, c.12/13m in length.

 

[jason -and the arguenauts]

I am also skeptical of the 'capacitive coupling' achieved by various lengths of wire arranged inside the hull. As most hulls grp thickness is measured in mm which makes the spacing between the wire and the conductive sea rather large and the capacitance is proportional to surface area, I suspect that the actual value of capacitance achieved is fairly small. If I have a minute I will try and estimate a value and see whether the effect is worthwhile at the frequencies involved.

How about me coupling internally to the stainless studs that run into the lead keel, itself coated with epoxy to maybe half a mm and then coppercoat on top. I would have thought that would give reasonable capacitative coupling to the sea water as a ground plane but it's 40 years since I did any electronics so I dont know.

Comments please.

 

[john_morris_uk]

How about me coupling internally to the stainless studs that run into the lead keel, itself coated with epoxy to maybe half a mm and then coppercoat on top. I would have thought that would give reasonable capacitative coupling to the sea water as a ground plane but it's 40 years since I did any electronics so I dont know.

Comments please.

You won't do any harm coupling your atu ground to your keel. The area will be relatively large (compared to a wire) and if the coating is as thin as you say, then I suspect that the coupling will be relatively good.

If you are worried about stray currents from the set up inducing electrolytic action put a 0.1 microfarad high voltage (and high RF current capacity) capacitor in series with the ground connection. A good RF specialist will sell you an appropriate capacitor for a couple of pounds or less.

The trouble with all these arguments about what makes a good ground connection is that if the propagation is good, then there is a HUGE leeway in signal to noise ratio available. Its only when conditions are marginal that small increases in efficiency become valuable.

For those others who have suggested that they use a wire internal to their boat as a counterpoise on the 80M amateur band, there are two points worth noting. Firstly for a counterpoise to be effective it needs to be a quarter wavelength long and a quarter-wave length of wire is 66 feet at 3.5 MHz. Secondly, a backstay antenna acts as a bottom loaded vertical, and the efficiency of such antennae is DIRECTLY proportional to its earth resistance. In other words, do EVERYTHING to improve the ground connection. (For those who are interested this is one of the reasons why the BBC Radio 4 198 Khz antenna is built where it is at Droitwich. Its a top loaded vertical and its in an area where the water table is very high which makes it easier to get a good ground connection.) The good news is that for those who use HF SSB at sea, seawater is a very good conductor and its why yacht backstay verticals tend to work so well so long as you achieve a good connection to the surrounding saltwater.

With respect, just because someone gets away without such a connection doesn't make their installation one for others to copy.

 

[MM5AHO]

"The trouble with all these arguments about what makes a good ground connection is that if the propagation is good, then there is a HUGE leeway in signal to noise ratio available. Its only when conditions are marginal that small increases in efficiency become valuable."

Thats perhaps the most important point made here.

On 80m counterpoises... they don't have to be in a straight line, but do need to be about the right length (electrically).

I did speak to a French boat once that was using an earth wire directly in the sea (trailed astern!).

Interesting point about 198 kHz Droitwich. But 198kHz Westerglen is on poor ground, and is well audible to the north beyond Iceland.

 

[jason -and the arguenauts]

"The trouble with all these arguments about what makes a good ground connection is that if the propagation is good, then there is a HUGE leeway in signal to noise ratio available. Its only when conditions are marginal that small increases in efficiency become valuable."

I can vouch for that. Using the backstay on my cat and with no more earth than the wire guardrails, I could happily chat to hams in both Siberia and South American using just 100 watts on 14mc/s. I was anchored in Northern Spain at the time.

In fact I didnt really notice any difference between using the bronze under hull plate, the guardrails or not bothering at all. Which doesnt mean that there was no measureable difference just that there was a good deal of leeway before my signal was too weak to read.

 

[john_morris_uk]

I can vouch for that. Using the backstay on my cat and with no more earth than the wire guardrails, I could happily chat to hams in both Siberia and South American using just 100 watts on 14mc/s. I was anchored in Northern Spain at the time.

In fact I didnt really notice any difference between using the bronze under hull plate, the guardrails or not bothering at all. Which doesnt mean that there was no measureable difference just that there was a good deal of leeway before my signal was too weak to read.

Its a good point well made. However the other trouble with counterpoises is that they are only effective for the frequency that they are a quarter-wave on. Maybe your guard rails happened to be a low impedence at 14 MHz by co-incidence?

Take your pick - but a good ground connection is the best of all, and especially for a wide range of frequencies.

 

[Beadle]

Don't know what size your cat is but I cant help thinking that there would have been one or two - maybe as many as four fairly hot spots on the guard rails when you were on transmit.

Intersting to use a simulation programme to model the currents and voltages on some of these odd arrangements. Its worth thinking about about - an rf burn can be intensely painfull - especially when delivered by a pair of 813s glowing cherry red with a VHF parasitic. It can upset a lot of TV viewers too. - Happy Days