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Old 01-03-2018, 19:07   #1
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New SSB install - ground-strap via diesel tank?

I'm currently installing a AT130 onto new mounts I've glassed into the area of my lazerette as close as possible to a deck-gland that is right next to the chain-plate of my insulated back-stay, such that I can run the antenna out and up to the backstay (clamp).

My issue is that my nearest thru-hull is the raw-water intake for engine, located around 8 feet forward of the lazerette-cabin bulkhead. Just forward of said bulkhead, amidships, is the stainless diesel tank (which is bonded to all the thru-hulls). The raw-water intake thru-hull is located between the forward end of the diesel tank and engine itself. The distance from the tuner to the thru-hull would be about 14' if I take into account routing etc.

Can anybody think of a reason why I cannot run my 3" copper braiding (for the RF ground) from the AT130, along to the back of the diesel tank, connect it to the tank, and then link the front end of the tank to the thru-hull with another section of 3" braid. Obviously, i'd plan on epoxying over the top of the run to protect from the atmosphere. The diesel tank doesn't have any electrical connections other than the bonding wire.

I also have the stainless structural studs of the [sizeable] stainless radar-arch/solar-arch/dingy-davit literally 5" away from the ground point on the tuner that I could also connect in..

The diesel tank has quite a substantial surface area, so would appear on the outset to be a better (and simpler) choice than 3" copper alone. Can anyone think of a good reason why this would be a bad idea?

For example, would the tank mess-up the integrity of my RF-ground connections? If the backstay was to carry lightning down to the tuner, could I risk blowing a hole in my diesel tank?

I'm hoping John (ka4wja) may be able to chime in here too, as I'd appreciate his input!

Thanks for the help,

Phil
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Old 02-03-2018, 11:29   #2
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Re: New SSB install - ground-strap via diesel tank?

Bump..
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Old 02-03-2018, 11:51   #3
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Re: New SSB install - ground-strap via diesel tank?

OK, I don't think that this is a dangerous idea, as long as you can prevent any galvanic corrosion. But it bothers me for some reason.

You might interfere with any tank fuel-level senders, if that's an issue for you. You might also want to use a capacitor isolator on the RF ground (https://sailmail.com/wp-content/uplo.../Grounding.pdf).
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Old 02-03-2018, 12:16   #4
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Re: New SSB install - ground-strap via diesel tank?

It's not uncommon to tie in any and all large metal objects to help RF grounding although a thru hull is usually all you really need. Remember to use copper strapping 3" or more across and never wire as the RF ground travels on the surface of the copper.
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Old 02-03-2018, 15:52   #5
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Re: New SSB install - ground-strap via diesel tank?

I find it interesting that people that push RF into the ether using multi-strand stainless steel antennas insist on using copper for grounding. I have always used stainless steel strap or tape for grounding. Never a problem with RFI. Also, I avoid round conductors in any ground paths connected to transmitters. The reason of course is the round conductors are inductive and flat wide conductors are not.

https://www.grainger.com/product/TAP...il-Tape-15D571
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Old 02-03-2018, 16:10   #6
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Re: New SSB install - ground-strap via diesel tank?

Phil,

You're making this way too complicated, maybe in the belief that you need a direct connection to seawater (you don't) and/or that you need to tie in lots and lots of metal like tanks and other structures....(again, you don't). These are largely old wives tales which have survived way too long.

In fact, from what you've described you could fashion a pretty good RF ground system very simply in one of two ways:

1. use the s/s arch structure....you said it's only a few inches from the ground lug on the tuner; or

2. use a simple ground radial system, like the KISS.

Either would likely work quite well. I'd try the arch first, since it's so close, and it may be totally satisfactory for you.

The KISS system works quite well, despite what "learned" tests and posts have claimed. In fact, there are literally thousands of setups where it has performed very well, including on my own boat and on those of many clients.

But, you may not need it. Try the arch and see what happens.

Bill
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Old 02-03-2018, 16:25   #7
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Re: New SSB install - ground-strap via diesel tank?

Quote:
Originally Posted by Paul Elliott View Post
OK, I don't think that this is a dangerous idea, as long as you can prevent any galvanic corrosion. But it bothers me for some reason.

You might interfere with any tank fuel-level senders, if that's an issue for you. You might also want to use a capacitor isolator on the RF ground (https://sailmail.com/wp-content/uplo.../Grounding.pdf).
You can prevent creating a DC "couple" by connecting through a capacitor. I suggest a 0.1 microfarad ceramic or ideally silver-mica capacitor with a voltage rating of at least 1,000 volts (more is better). If you sail in a area prone to lightning, keep in mind the likely effects of passing a few thousand amps through whatever you are using for a "ground". For example, if you connect your "ground" to your engine block, what happens to your crank shaft bearings when all that current passes through on its way to the prop and prop shaft? Nothing good, I'm sure.

For HF SSB communications, what you want is a long ground plane / counterpoise. A through hull fitting isn't adequate. What I do is trail 50 feet (longer is even better) of 1 inch wide braided stainless steel strap attached to the backstay chain plate. You can get the strap from American Grounding Systems: Ground straps and braids, ropes & wires by AGS. Online Catalog and Custom Design- SAMPLE REQUEST -tinned and bare copper, nickel plated copper, stainless steel, braided ground straps. Look under "braided braid stock." And if you dissipate a lightning hit through that - nothing bad happens.

Please, PLEASE avoid using a bronze "dynaplate" attached to your hull. If you ever take a serious lightning hit, you will see what happens when all that energy is dissipated into non-compressible water right next to your hull. It's like hitting a mine. Using only a through hull as your "ground" will have the same effect.
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Old 02-03-2018, 18:02   #8
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Re: New SSB install - ground-strap via diesel tank?

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Originally Posted by btrayfors View Post
Phil,

You're making this way too complicated, maybe in the belief that you need a direct connection to seawater (you don't) and/or that you need to tie in lots and lots of metal like tanks and other structures....(again, you don't). These are largely old wives tales which have survived way too long.

In fact, from what you've described you could fashion a pretty good RF ground system very simply in one of two ways:

1. use the s/s arch structure....you said it's only a few inches from the ground lug on the tuner; or

2. use a simple ground radial system, like the KISS.

Either would likely work quite well. I'd try the arch first, since it's so close, and it may be totally satisfactory for you.

The KISS system works quite well, despite what "learned" tests and posts have claimed. In fact, there are literally thousands of setups where it has performed very well, including on my own boat and on those of many clients.

But, you may not need it. Try the arch and see what happens.

Bill
WA6CCA
I believe that trailing a flat stainless strap while under way, like I described above, works best. It however doesn't work well when not trailed while you ae not underway.

Bill is right: you don't need a direct connection to the sea. A simple ground radial system inside your hull will give you capacitive coupling through a fiberglass hull to the sea.

Bonding that grounding system to other interior metal objects will provide some protection from "side strikes" in the event of a lightning hit. If you sail in areas with very dry air, providing a DC path-to-seawater will eliminate the static noise caused by corona discharge ("St. Elmo's Fire"), but that can be anything. The current is miniscule, so a small wire trailed in the water is sufficient, if you ever encounter the effect.

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Old 03-03-2018, 14:02   #9
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Re: New SSB install - ground-strap via diesel tank?

Not being an electrician I have a bad feeling about it: what if the s't hits the fan/lightning strikes the SSB-set? I wouldn't want a diesel tank anywhere near that...
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Old 03-03-2018, 15:41   #10
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Re: New SSB install - ground-strap via diesel tank?

Quote:
Originally Posted by Viking Sailor View Post
I find it interesting that people that push RF into the ether using multi-strand stainless steel antennas insist on using copper for grounding. I have always used stainless steel strap or tape for grounding. Never a problem with RFI. Also, I avoid round conductors in any ground paths connected to transmitters. The reason of course is the round conductors are inductive and flat wide conductors are not.
Depending on the antenna geometry and frequency, the ground currents may be much higher than the antenna currents. That's why copper works well.

And *all* conductors are inductive. The main advantage of flat conductors is that for a given conductor cross-section they have a greater surface area than round wires, and *less* inductance. It's the skin effect.

A stainless strap probably works just fine, but a copper strap will be (perhaps not enough to make a difference) better.


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Not being an electrician I have a bad feeling about it: what if the s't hits the fan/lightning strikes the SSB-set? I wouldn't want a diesel tank anywhere near that...
Fuel tanks are often grounded anyway, if only via the tank-level sender wiring. I don't think the antenna / radio ground is any more dangerous than the rest of the grounded mast and rigging.
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Old 04-03-2018, 12:28   #11
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Re: New SSB install - ground-strap via diesel tank?

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Originally Posted by btrayfors View Post
The KISS system works quite well, despite what "learned" tests and posts have claimed.
Hmmm. What "learned" tests claim that it does not work?

I haven't seen any myself, certainly not on this forum. I have seen tests that show it doesn't have the unique properties the seller claims, but those tests don't show, or attempt to show, that it doesn't work as a functional RF ground/counterpoise.

Chip
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Old 04-03-2018, 13:58   #12
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Re: New SSB install - ground-strap via diesel tank?

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Hmmm. What "learned" tests claim that it does not work?

I haven't seen any myself, certainly not on this forum. I have seen tests that show it doesn't have the unique properties the seller claims, but those tests don't show, or attempt to show, that it doesn't work as a functional RF ground/counterpoise.

Chip
Agreed. I've been working with RF and designing antennas for decades, I don't have any complaints about the design. Capacitive coupling is sufficient, and I'd only add copper mesh wherever convenient to increase the surface area since the effectiveness of the coupling is directly proportional to the surface area. Here's a good source: GEORGIA COPPER - Copper MESH

One caveat about copper: it dissolves in sea water, so keep it out of the bilge, where it won't last long. I run a stainless strap through my bilge.


The reason there are so many opinions about antennas is: there are no ideal broadband antennas. It's all relative. If it works for you, then it works!
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Old 04-03-2018, 15:28   #13
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Re: New SSB install - ground-strap via diesel tank?

Thanks everyone for your input!

I was quite happy with the direction I was going with, and my basic knowledge of the physics involved, until I started reading more.. and man, are there a lot of conflicting opinions out there, along with a healthy sprinkling of pseudo-science! I'd gone from being sensible and logic-based to being racked with self-doubt and concern... that's what too much internet research will do for you!

Based on everyone's feedback (see below), I'm going to go the following path:

Connect to SS arch using tinned-copper (or SS) braid. See how the tuner functions (time to tune/re-tune) and follow-up by using the "rolled-out floating aluminum foil in the water" comparison method.

Then, connect ANOTHER strap to the metal diesel tank (which isn't electrically connected to anything else - I use ultrasonic tank monitors). I will not then connect this onto any thru-hull. I'd do the same test again. I'm assuming at this point, that adding more and more metallic surface area to the ground-lug is going to improve the tuner's ability to find a match easier and easier.

If all works well, I may even be tempted to select a few of my favorite/usual frequencies, and then make 1/4 wavelength radials out of braid (and protect with heat-shrink over the top), bind them together at one end, connect to the ground-lug and stretch them out... almost like making my own KISS, but using higher-surface area braid, rather than copper wire.

Thoughts?

I'll report back with results - bearing in mind that my contact's reported signals will be anecdotal at best, as I don't have the equipment to start making good SWR assessments etc.

Thanks again!

Phil




Quote:
Originally Posted by Paul Elliott View Post
OK, I don't think that this is a dangerous idea, as long as you can prevent any galvanic corrosion. But it bothers me for some reason.
Thx. I will endeavor to avoid tying to the bonding system.

Quote:
Originally Posted by robert sailor View Post
It's not uncommon to tie in any and all large metal objects to help RF grounding although a thru hull is usually all you really need. Remember to use copper strapping 3" or more across and never wire as the RF ground travels on the surface of the copper.
Yes, RF travels on surface of the conductor, so I plan on using copper (or stainless) braid of sufficient surface area.

Quote:
Originally Posted by btrayfors View Post
1. use the s/s arch structure....you said it's only a few inches from the ground lug on the tuner; or
2. use a simple ground radial system, like the KISS.
Either would likely work quite well. I'd try the arch first, since it's so close, and it may be totally satisfactory for you.
The KISS system works quite well, despite what "learned" tests and posts have claimed. In fact, there are literally thousands of setups where it has performed very well, including on my own boat and on those of many clients.
But, you may not need it. Try the arch and see what happens.
Bill
WA6CCA
I like this approach. Thank you!

Quote:
Originally Posted by Cpt Pat View Post
If you sail in a area prone to lightning, keep in mind the likely effects of passing a few thousand amps through whatever you are using for a "ground". For example, if you connect your "ground" to your engine block, what happens to your crank shaft bearings when all that current passes through on its way to the prop and prop shaft? Nothing good, I'm sure.
The bearings would most likely spot-weld the shafts and bind - rendering the engine junk..

Quote:
Originally Posted by Cpt Pat View Post
If you ever take a serious lightning hit, you will see what happens when all that energy is dissipated into non-compressible water right next to your hull. It's like hitting a mine. Using only a through hull as your "ground" will have the same effect.
This is a good point - and has made me think again about connecting to the raw-water intake for the same reason - have a prominent discharge path through a thru-hull that could (in certain cases) be blown out of the hull under the engine! I'm not sure how likely this is, but if I can avoid connecting to a thru-hull, then I should.. (will rest easier in an electrical storm when I have my spare VHF etc stowed in the oven!)
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Old 04-03-2018, 19:16   #14
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Re: New SSB install - ground-strap via diesel tank?

In my experience the best test of your SSB is on lower frequencies..usually if you can get real good transmitting on 4 or 6 megs you will have set up a real good counterpoise. Many marginal set ups will transmit well on higher frequencies but not so well on the lower ones. Also if you can get to a keel bolt it also is usually all you will need. Good luck and I'll look forward to hearing your results. R
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Old 04-03-2018, 19:38   #15
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Re: New SSB install - ground-strap via diesel tank?

Quote:
Originally Posted by Cpt Pat View Post
You can prevent creating a DC "couple" by connecting through a capacitor. I suggest a 0.1 microfarad ceramic or ideally silver-mica capacitor with a voltage rating of at least 1,000 volts (more is better). If you sail in a area prone to lightning, keep in mind the likely effects of passing a few thousand amps through whatever you are using for a "ground". For example, if you connect your "ground" to your engine block, what happens to your crank shaft bearings when all that current passes through on its way to the prop and prop shaft? Nothing good, I'm sure.

For HF SSB communications, what you want is a long ground plane / counterpoise. A through hull fitting isn't adequate. What I do is trail 50 feet (longer is even better) of 1 inch wide braided stainless steel strap attached to the backstay chain plate. You can get the strap from American Grounding Systems: Ground straps and braids, ropes & wires by AGS. Online Catalog and Custom Design- SAMPLE REQUEST -tinned and bare copper, nickel plated copper, stainless steel, braided ground straps. Look under "braided braid stock." And if you dissipate a lightning hit through that - nothing bad happens.

Please, PLEASE avoid using a bronze "dynaplate" attached to your hull. If you ever take a serious lightning hit, you will see what happens when all that energy is dissipated into non-compressible water right next to your hull. It's like hitting a mine. Using only a through hull as your "ground" will have the same effect.
What if you bolt down the end of the 3"copper strap to one of your keel bolts on a iron keel?
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