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Old 10-10-2017, 02:21   #16
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Re: Grounding Plate for SSB

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Originally Posted by Guy View Post
What is the resistance of marine growth? All the little passages in a Dynaplate fill up with it. A bare copper plate is covered with it in no time
The real question is "What is the capacitive reactance of marine growth?".
It is probably low but I have never tried measuring it
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Old 10-10-2017, 07:16   #17
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Re: Grounding Plate for SSB

Anything in water has very high capacitance (low reactance). Even marine growth is mostly just water which has a very high dielectric constant. Don't worry about growth on the grounding plate reducing the effectiveness. Growth doesn't hurt anything.

I disagree that just throwing some copper foil in the bilge will be an effective solution. Also, don't listen too much to the "hey, it works for me" stories either. What works best based on physics is a short copper strap well connected to a through hull (or dyna plate). A large area of copper foil against the hull below the water line also works well. The foil can be arranged in a grid to reduce the amount of foil needed. Ten square feet is a good starting point to be considered "large". Make sure where foils cross one another they are well connected together with bolts or solder (solder is best).

Proper grounding of the tuner does several things:

1) increases signal transmitted from antenna.
2) reduces VSWR at the transmitter.
3) reduces RF energy coupled into other electrical systems on the boat (e.g. autopilot, instruments, VHF, lighting, etc.).
4) increases the range of frequencies the tuner can effectively match.

There is more to it than "can anybody hear me?".
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Old 10-10-2017, 08:16   #18
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Re: Grounding Plate for SSB

People are throwing around terms here rather loosely.

First, anything (e.g., thruhull, dynaplatess etc...) in physical contact with the water has no capacitance.

And dielectric is an insulator, not a conductor. Water isn't a dielectric.

Misusing terms serves only to confuse.
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Old 10-10-2017, 09:31   #19
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Re: Grounding Plate for SSB

Radio frequency passes through a dielectric. The wavelength and reactance is a function of dielectric constant. Water has a very high dielectric constant and therefore has low reactance to radio frequencies. It does not insulate at radio frequencies. I know what the terms mean.
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Old 10-10-2017, 09:56   #20
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Re: Grounding Plate for SSB

I am not a yacht grounding expert, but have 40 years professional experience with antenna work and lightning protection.

Here is what I do and why:

Impedance (in Ohms) is the correct unit for measuring quality of "ground" connection - in reality this is a mix of conductive boat parts and seawater. There will be antenna return currents flowing through both.

Impedance combines resistance with reactance - which, when considering connection to seawater is usually capacitive. A pure capacitor can be visualized as two parallel conductive plates - not touching - therefore no DC can flow, and measured resistance is very high - an insulator.

But here is the concept - Radio Frequencies ("RF") will pass through a capacitor very well - the more capacitance, the more RF current can flow. No need for DC conduction. The greater the plates' surface area, and the closer the spacing, the more capacitance.

The nature of the insulator or semiconductor between the two parallel plates also influences the amount of capacitance. This quality is known as dielectric constant (also permittivity) see: https://en.wikipedia.org/wiki/Relative_permittivity


If you're still with me, note that air or vacuum has a Dielectric Constant of 1.0 ... seawater is somewhere around 50 or higher.

For an RF "ground", a current path to the seawater is a good idea - not absolutely essential - see other discussion of "counterpoise."

On my boat I happen to have a very large capacitor plate with lots of area very close to seawater. Mine weighs 3000 pounds and is made of very conductive lead. And its spacing to the other "plate" is the thickness of paint - which itself has a much higher dielectric constant than air. I even have convenient connection studs coming up through my bilge. In some areas of the capacitor plate the paint is scraped off, making some direct contact with seawater - but this DC conductance is of little consequence compared to the very large value of capacitance my keel has to the sea.

Some authorities recommend against connecting anything else to the keel except your 40 foot lightning rod. But given that all the rigging is connected, and that wiring and radio cables are inside the lightning rod, I contend that you are only fooling yourself if you believe you can isolate your boat wiring and ground (-DC) from lightning stroke currents, whether a direct hit or induced from a nearby hit.

A key tenet with protecting electrical systems and electronics from lightning damage is keeping all the ground connections at the same voltage (relative to the ocean in this case) during a strike. This is achieved to a greater or lesser degree by connecting ground systems together at a single point - usually at the best "ground" connection point. This minimizes the lightning current flowing between electronic equipment.

One of my keel bolts has an 18" heavy copper cable directly to my mast. Another bolt has a wire to the common DC- connection, and yet another (copper strap work best for this) cable goes back to the antenna tuner for the RF ground.

Note: A bronze thru-hull does not have much surface area in contact with seawater. Its not enough for a good RF ground, and I float all of mine out of fear of stray electrolytic currents eating them.

Note two: If I used a separate hull plate to augment my RF ground, I would run a copper strap directly to my central ground connection - the keel. Don't want it at a different voltage during a strike.

Note three: Antennas, grounding, and lightning protection are complex subjects. I hope I have not added to the confusion.
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Old 10-10-2017, 10:03   #21
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Re: Grounding Plate for SSB

SSB ground plane. Using copper ribbon, 3 or 4 inches wide bolted to engine, any metal tanks, metal toe rail, stanchions,etc. makes a great counterpoise. No dynaplate needed. No more holes in the boat. I used 6 inch wide sail repair tape to adhere the 4 inch wide copper foil ribbon inside the hull of my boat.
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Old 10-10-2017, 11:16   #22
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Re: Grounding Plate for SSB

I bought a used boat that had an SSB with a through hull grounding plate and I could not get the radio to work until I switched to a KISS counterpoise. I'm not sure why the grounding plate did not work. Most likely it had to do with corrosion. Apparently, this can be a problem even if the corrosion is on the surface of the copper strip that connects the grounding plate to the radio. RF energy travels on the surface of the conductor as opposed to through the cross section like electricity. The KISS is so much simpler, reliable, and robust. You just connect it to your radio and stretch it out in the bilge. Then you can forget it. It works so much better that I had my grounding plate removed and the hole glassed over.
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Old 10-10-2017, 12:28   #23
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Re: Grounding Plate for SSB

A bit more food for thought on the counterpoise principle and the capacitor.

For those who rode along with me on my somewhat laborious explanation of capacitors, understanding this concept of RF flowing through two conductive plates that are insulated to direct current ... (Radio Frequency ("RF") is high frequency alternating current ("AC"). AC flows through capacitors.)

Think about this: the antenna itself - (in most cases) a fully insulated back stay wire rope - is one side of a capacitor. Excepting additional magnetic couplings, this simplified analogy is remarkably correct.

The other plate of the capacitor is anything conductive and nearby, including seawater, DC wiring, mast, shrouds, lifelines, and metallic toe rails. RF current flows in all of these, and when connected together, form a counterpoise - which is essentially the other plate in the capacitor.

Those conductors that attract the most current are the closest and those with the most surface area - just like a capacitor.

Now I'll shut up.

Chris
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Old 10-10-2017, 12:30   #24
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Re: Grounding Plate for SSB

I’m retired from 45 yr in RF telecommunications and a near life long ham and cruised extensively. There is always a lot of ‘varible’ information here on complex issues, such as SSB HF installations. Even local Marine Electronics business great on plug & play radar, GPS, sonar, Marine FM installs, often employ terrible practices on SSB installs... so be careful with word of mouth information that your life may depend on someday.

Yes I have worked over 100 countries on very poor marine antennas (even sometimes using as little as 5 watts)... but I use the most favorable propagation times/ frequencies and the stations usually are land based with very good antenna installations/ power. When the chips are down, lighting is everywhere, and you’re 100 miles off shore and maybe 500-1000 miles from someone who can help/ get information to/from... and you’re best option might be another boat with limited antenna and suffering your same atmospheric noise... you want the BEST SSB installation you can reasonably have. Also consider that your main SSB antenna could become damaged and you’ll need to rig just a random length wire up the flag halyard... you’ll need the best ground/ counterpoise system you can possibly get to partially make up for the make-shift antenna.

Seems to me if you’re going to be out of the water anyway... this is the time to install the very easily installed through the hull DynaPlate. It’s just two holes through the hull and some 5200. Takes about 15 minutes to decide where to install it and about ten minutes to actually do the simple installation.

Why do I think you/ others should reconsider the comments that it’s not necessary? I have 2” wide copper foil from stern to bow epoxied/ waterproofed down, one of the mail-order pre-assembled counterpoises, and the DynaPlate. As a test, to convince another cruiser, I disconnected all of them and one-by-one reconnected them, and then various combinations of two of them.

First I showed him that even with no RF ground at all ground we could still receive stations... pretty well. But when we transmitted the turner wouldn’t/ couldn’t properly tune causing to transceiver to power down to only a few watts to protect itself from the high SWR. So just because you can receive some signals is not the yardstick to rely on regarding how well you will be heard.

Then I connected what I knew was the least effective RF ground/ counterpoise... the one the cruiser was using (the store bought 23’ counterpoise that you pull through boat that he insisted he got excellent signal/ reports. Yes it worked and he said ‘SEE’ works great seeing a so-so S-meter reading and hearing the station. Now we called the station and asked how he was hearing us. He response was ‘OK’. Then I connected my stern to bow straight 2” wide Cooper foil (46’ ketch) and asked how do you hear us now? The response was ‘wow, what did you do... turn the power way up! Then we disconnected the store counterpoise... and the station said still very strong/ no difference.

Then I disconnected everything again and connected just the through the hull DynaPlate RF ground and the station said it seems just as strong as the stern to now Cooper foil. But when we also connected the Cooper foil to the DynaPlate the station reported the signal went up even further.

Conclusion:
1) the store bought 23’ counterpoise is maybe just barely ok in a pinch/ emergency but not the best option, by far, if you are doing serious off-shore cruising. (... and added nothing to an already good RF ground system.)

2) Just a DynaPlate or well installed 2” aft to bow Cooper foil are acceptably good alone. But for your best signal/ redundancy, especially since you already have the makings of a Cooper foil installation, I recommend BOTH a DynaPlate and the aft to bow Cooper foil.

Now about the Cooper foil installation (and why I feel strongly about why you should still install the DynaPlate)... first, the Cooper foil MUST be as straight as possible. RF does like 90 degree bends... it’s effectiveness almost stops at the first bend. So if you thought you had a 40’ Cooper foil RF ‘ground/ counterpoise... depending on how many 90 degree turns you have you may only have the actual performance of 10-15 feet. And worse, if you don’t epoxy it to the hull/ seal it from hull condensation/ salt infiltration... it will soon corrode badly and actually corrode to failure in a few years in a ‘wet Boat’ leaving without knowing it... no RF ground/ counterpoise... maybe when you really need to have effective HF SSB for emails/ wx/ emergency. And even before it fails, RF ‘travels’ only on the skin of conductors so as the foils starts to turn green... that corrosion is actually creating significant ‘resistance’ to the RF and reducing its needed performance... even if beyond the surface the Cooper is in good shape.

After the easy Dynaplate installation and connection to the tuner/ transceiver there is nothing to do except don’t paint it with bottom paint/ anything... wire brush it during any hull cleanings/ haulouts.
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Old 10-10-2017, 12:49   #25
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Re: Grounding Plate for SSB

I covered my "barn door" rudder with copper sheet (roofing material) below the waterline. This put it directly below the tuner, mounted in the lazarette on the inside of the transom with a short run to connect them. (The backstay is the antenna.) This has worked very well for me. I have not painted the copper so there is occasional scraping needed - perhaps I should paint the copper and count on capacitive coupling instead? Aside from the fouling, the copper does slowly erode, especially in the prop wash. I have replaced it once. Lifetime would depend on the amount of motoring but I would estimate 20 years more or less in active use.

Dynaplates are another story. I have had 2 of them mounted. One of them is slowly eroding while the other looks good (these are about 30 years old). The problem that has been reported for SSB counterpoise use is that they fill up between the small beads, with corrosion, sediment, and growth, and with time act more like a solid plate with reduced performance. Since I haven't used them for the antenna I can't confirm the performance issues (that were commonly reported in the past) - I can confirm that they eventually turn into a solid mass. The recommended solution is to remove them and soak in acid to dissolve the minerals and corrosion. When I have done that it clearly cleaned the surface but not so much into the matrix. If it were done regularly it might keep them cleaned out. (To be clear: these sintered bronze plates work because the many beads present a large surface area to the water - if water, or some other conductive substance, is not in the interstitial spaces the effective area will plummet; minerals and oxides are usually insulators, not conductors.)

Copper laid in the bilge is usually acting as a ground mass. Capacitance coupling through the thickness of a hull is not going to be very strong (the capacitance of two plates is linearly related to area and inversely related to distance between them). Not that it matters: a ground mass can work well.

While I have had a good experience with the copper clad rudder, I have purchased a KISS ground radial system to try. There is no magic here; a set of ground radials cut to the appropriate lengths for the various bands should work very well. It would be easy enough, and much less expensive, to DIY the ground radials but for the money it is convenient and they do a nice job.

Greg
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Old 10-10-2017, 14:17   #26
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Re: Grounding Plate for SSB

Well, some of you folks went way over my head!

If hauling anyway I may install the dynaplate and not hook it up until someone with intimate knowledge of the SSB helps me test it. I liked the testing mentioned where individual ground components were tested and then various combinations linked together were tested. But again, I will seek help for that testing!

Hey, somebody may get a cash paying tester job somewhere between Lauderdale and Tampa!
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Old 10-10-2017, 15:25   #27
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Re: Grounding Plate for SSB

If you install the Dynaplate then you might as well hook it up (unless that's going to be really difficult, and then why bother?) Extra ground connections, whatever they are, can only help. (Generally speaking. I'm sure we could contrive an example where an extra ground caused a problem, but that's extremely unlikely.)
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Old 10-10-2017, 17:19   #28
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Re: Grounding Plate for SSB

I am ripping the SSB out of my boat. About two months ago when I was inland, I get a call from the marina that my high water alarm was sounding off. Long story short, the boat almost sunk getting it to the yard. The through hull bolt corroded out and water came on in. Once found under the floor board, a pencil stemmed the tide until repairs were made. The SSB is old with a blurred screen so probably doesn't even work. I will replace if I get back in the islands. Not sure they are all that useful anymore. I know there are some networks in the islands that are useful and fun for info. Just mad at this point so want to junk it.
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Old 10-10-2017, 17:43   #29
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Re: Grounding Plate for SSB

Quote:
Originally Posted by transmitterdan View Post
I know what the terms mean.
With your forum name I would think you would.

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Old 11-10-2017, 07:27   #30
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Re: Grounding Plate for SSB

Kiss SSB. Got it as only "radio earth" counterpoise. Works great! Connected to ground lug on the auto tuner. Tuner tunes 40 feet wire from mast to aft end of the boat. Tunes all frequencues from 1.6 to 29MHz.
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