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Old 09-10-2018, 03:06   #1
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HF/SSB

Can I use a woven copper braid as a grounding strip in my HF installation?
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Old 09-10-2018, 03:56   #2
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Re: HF/SSB

Short answer yes, but you are supposed to get the best effect with copper plate or ribbon, and it has to be quite wide, but I have in the past just used a battery cable, which worked, but the earth does have a big effect on transmission.
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Old 09-10-2018, 04:28   #3
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Re: HF/SSB

I've used shielding braid as a connector between tuner and grounding point in the past and it did work. Purists will bleat that flat Cu ribbon is the only way that works, and indeed it is best, but often hard to route around a boat's interior.

IN my eye, the downside of such is that it corrodes quickly and detrimentally. Can become useless in a few months, while the ribbon lasts years, even in damp bilge areas.

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Old 09-10-2018, 04:57   #4
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Re: HF/SSB

I must be a semi-purist then. Yes, braid can be used but it is distant second to best practice. I have used it when nothing better was available but the RF impedance is way higher with braid compared to flat ribbon. As Jim points out, corrosion is serious issue and it's RF impedance increases as a result.

You can fit it in place and then tin it with solder to make it into "flat ribbon". This makes it better and increases it corrosion resistance.

Copper water pipe is a better alternative to copper braid if it can be made to fit IMO.

It is all about RF skin effect.
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Old 09-10-2018, 06:15   #5
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Re: HF/SSB

Quote:
Originally Posted by Jim Cate View Post
Purists will bleat that flat Cu ribbon is the only way that works, and indeed it is best, but often hard to route around a boat's interior.
Yep. Flat ribbon may be best, but you have to remember the old saying that "perfect is the enemy of good enough." Just about anything will work in a pinch. A plain old piece of copper stranded wire will often work "good enough."


Of course I would point out that there can be some confusion when using the word "ground." Technically speaking, what we are talking about here is the antenna counterpoise, often referred to as the antenna ground. Quite a different thing from electrically grounding the radio chassis, which is also generally recommended.
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Old 09-10-2018, 14:08   #6
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Re: HF/SSB

Thank you for the replies. I am talking about the counterpoise. On our new to us boat it is made up of 100mm and 50mm copper strip. The copper strip between the coupler/ tuner and the external ground plate is very discoloured in the engine room but seems to be solid underneath, elsewhere it is badly corroded and eaten away, hence my original question as I have found a roll of copper braid on board.
The Transceiver is not grounded to the earth plate, would it improve matters if it was?
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Old 09-10-2018, 15:23   #7
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HF/SSB

Most just use the Ocean as the couterpoise. I have a large Dynaplate, others will just connect to a thru hull.

Then others will use the rub rail as a counterpoise, some will put copper though out the boat, and some will buy the pre made counter poise, that some say is junk and others say is the best.

Using the ocean seems to be the most common and has been done for a long time.

I donít think connecting the transmitter to the Dynaplate will help anything.

I would replace your strapping with one piece. These people had good prices and is where I got mine, I went with three in wide I think and stupid thick.
https://www.gacopper.com
If itís going where it will get wet, maybe conformal coating isnít a bad idea. Conformal coating is like clear fingernail polish and is very often used to help water proof electronics, lots of marine stuff will have their circuit boards conformal coated.
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Old 09-10-2018, 16:14   #8
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Re: HF/SSB

Connecting the tuner to the Dynaplate or a Bronze thruhull with a flat wide Cu ribbon is all that is needed but use the woven braid if you have nothing else. Pretty much as others have already noted .

Best corrosion protection for the Cu ribbon IME, is to tin it with common solder, easy to do with a hot air gun. You can of course paint it or grease or do whatever you want to keep moisture and salt away from it.
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Old 10-10-2018, 11:26   #9
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Re: HF/SSB

Poppycat,
The really short answer is: No...don't use the copper braid...
Clean what you have, evaluate what is there, and if you need to replace it then use copper strapping (or even wire), but not the braid!!


Most of this is covered in the stickies at the top of the Marine Electronics page...
Please have a look, they will save you a lot of time and effort:

HF-SSB Radio, Proper Installation Tips/Techniques, etc.

Marine SSB Stuff (how-to better use / proeprly-install SSB, & troubleshoot RFI, etc.)


1) Remember that anything metallic can be used as an antenna and/or RF ground....it's all a matter of degree, and how long it lasts!! (and does it cause any problems)
And, while your Marine HF/SSB Radio will work without a "ground" at all, it will work better with a good antenna ground / RF ground....
(but fyi, most will work without a ground, better than they'd work if you had a poor ground that causes RFI and other noises/interferences....but...but, just install a good antenna ground / RF ground and you're all good!!)


2) For our end-fed vertical antennas....the key to having a good antenna ground / RF ground is to have as much RF conductive material (copper, sea water, metallic tanks, etc.) as clsoe to the base of your antenna as possible, and connect that to the remote tuner's ground terminal, with as low impedance connection as possible...
Hence a short (typically < 6' to 8') piece of 3" wide copper strap to a underwater ground plate, is the best over all approach!!

But, copper wire can of course be used....it just has significantly higher RF impedance than the wide / flat copper strap...so, you have a less effective ground...


3) Direct to your question:
a) Bare copper braid should never be used for RF....ever...especially in a salt air / sea water environ!
DC grounding, away from sea water / salt air, it's okay...but in those locales bare solid copper wire is used...

b) Tinned copper braid is still not recommended for RF use....as the tiny wires moving / making-n-breaking contacts can cause lots of problems at RF freqs...(especially being a big generator of RFI)

c) Epoxied / glassed-in, tinned copper braid is "acceptable" for RF use...as you've prevented both corrosion and the intermittents of the all the tiny making-n-breaking contacts....
But...


d) But, if someone was going thru all that trouble (in "c"), they'd have been much better off just using copper strap...(note that I'm using the word "strap" and not "foil")....
"foil" is thin, typically .001" to .003" thick and can be easily cut with scissors....it can also be torn / ripped by hand....and if used in a sea water / salt air marine environment without painting/coating/epoxying, it can quickly become eroded and torn....
"strap" or "strapping" is typically 012" to 040" thick, and cannot be cut with scissors, nor can you tear it by hand....while I always paint/coat it (so it lasts decades), even if left bare in the bilge it will last years...


I know you're downunder, but here are some pages with some good info...
https://www.gacopper.com/022-CopperStrap.html
https://www.gacopper.com/index.html
https://www.gacopper.com/Braid-Strap...omparison.html
https://www.gacopper.com/Link.html


As I wrote above, the key to having a good antenna ground / RF ground is to have as much RF conductive material (copper, sea water, metallic tanks, etc.) as clsoe to the base of your antenna as possible, and connect that to the remote tuner's ground terminal, with as low impedance connection as possible...
Hence a short (typically < 6' to 8') piece of 3" wide copper strap to a underwater ground plate, is the best over all approach!!


So...
So, while the original short answer is: No....
If you don't mind needing to replace it often as well as the high probability of it actually causing your transmit RFI problems, then yes you can use it...
Quote:
Originally Posted by Poppycat View Post
Can I use a woven copper braid as a grounding strip in my HF installation?
Of course the better answer is what I described above...


Are you using this to connect to your antenna ground / counterpoise???
That means are you using this to connect to an underwater bronze thru hull or underwater grounding plate, where you are using the sea water as your antenna ground??

If this is the case, while I still recommend strap and wouldn't recommend using a copper braid, you could use some insulated and tinned copper wire...assuming the length was short enough (one foot or so) the difference between an 8ga to 12 ga copper wire and strap would be slight....
If you have a longer run that that, I recommend 3" wide copper strapping...



Opps...Just saw your post with more information...
All above info / recommendations are still 100% good!!

I will elaborate here...in detail...
Quote:
Originally Posted by Poppycat View Post
Thank you for the replies. I am talking about the counterpoise. On our new to us boat it is made up of 100mm and 50mm copper strip.
Assume this is solid, flat copper "strip"?? (what I call "strap")...
If so, this is good!!!

If it was thick enough to be strap and not foil, it should still be good to use....just clean the ends that attach to the tuner ground lug and the underwater grounding plate terminal bolt...make it clean and shinny!
Attach securely....and then coat with grease or paint, etc. to protect the connection from sea water / salt air (I use a conductive grease called Penatrox-A....this is opposite of Tef-Gel, which is an isolating grease....but many just use any waterproof grease or just spray some paint on the junctions after assembly and tightening, and they're good to go!)


The copper strip between the coupler/ tuner and the external ground plate is very discoloured in the engine room but seems to be solid underneath,
Copper does discolor....that is normal....but the actual connection points need to be clean, and make excellent electrical / RF contact....so, make sure they are clean, shinny, and dry....and then tighten, and then protect them with something (grease, paint, etc...)
Again, if this "strip" is thick enough to be strap and not foil, then you're probably fine....just clean the ends where it makes contact...
BUT...

But, if it is thin foil (can you tear it with your hands, or cut it with scissors??), then it may have deteriorated beyond practical use, and will need to be replaced...


elsewhere it is badly corroded and eaten away, hence my original question
If it is "eaten away" it was probably thin "foil" and not "strap"....and as such should be replaced...
BUT...
But, when you say "elsewhere"...where is "elsewhere"???
As, the ONLY antenna ground / RF ground connection you need is a low-impedance connection between the remote tuner ground lug and the underwater grounding plate terminal bolt....
So, it is doubtful that you need to do anything except what I write here / above....

If there is "strip" running "elsewhere", it was probably connecting to metal tankage and/or a keel bolt??
And, this is another good practice (I do the same on my boat, in addition to 6" wide copper strap to two Dynaplates, I have 3" copper strap running to two wide metal tanks, and also to a keel bolt....), but it's considered overkill for most, since you already have a direct sea water connection for an excellent antenna ground / RF ground!!


hence my original question as I have found a roll of copper braid on board.
Do NOT use this copper braid....it will just make things worse!!


The Transceiver is not grounded to the earth plate, would it improve matters if it was?
No, it will not improve things....
And, in some (many) cases it can make matters worse!! (lots of details about this if you desire, but the short answer is as I stated...)


I do hope this helps??

fair winds

John


P.S.
Here is a pic of my 6" wide copper strapping (0.032" thick, and about 7' long from the tuner ground lug to the Dynaplate bolt) as it attaches to the Dynaplate bolts...and you can see the end of the 3" copper strap that goes forward to a keel bolt as well...this is after half dozen years....I did paint/coat the other strap that goes to the keel bolt, cuz it will get wet in the bilge, but these in the pic are just bare copper strapping...



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Old 10-10-2018, 16:01   #10
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Re: HF/SSB

RF flows on the thin outer layer of conductors, unlike DC which flows through the entire conductor. So an RF ground is traditionally made with "ground braid". Thin tinned wire (tined to prevent that outer layer from oxidizing and gaining resistance) that is braided into a flat strap, presumably because it is easier to run flat straps than thick cables. And if you look at the exposes surface area of a flat strap, versus a round cable? You get more surface area in the flat strap, too.

There are "skin effect depth" calculators on the web. For any given frequency (HF, VHF, UHF) you can actually calculate how deeply that RF frequency will travel in a conductor. If the RF only travels within 1/2mm or 1mm or the surface? Double that, for the two sides on a flat ribbon, and that's all the thickness you need. Anything more is just an expensive waste of copper, unless you are using it to carry DC or shunt lightning, or want the physical strength.

There really is old established science behind that stuff.
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Old 10-10-2018, 18:01   #11
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Re: HF/SSB

Quote:
Originally Posted by Poppycat View Post
Can I use a woven copper braid as a grounding strip in my HF installation?
Poppycat, I am facing a similar problem (see this thread: Compromise question for the HF fanatics - Cruisers & Sailing Forums)

I am chasing a price from John's recommended supplier, to see if they will post to Oz. Let me know if you are interested in a roll also as we may be able to offset postage costs somehow.

Or, if you can find a decent supply price here in Oz, please let me know, i have tried and failed so far to beat AU$25 per meter.
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Old 10-10-2018, 18:13   #12
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Re: HF/SSB

Quote:
Originally Posted by hellosailor View Post
RF flows on the thin outer layer of conductors, unlike DC which flows through the entire conductor. So an RF ground is traditionally made with "ground braid". Thin tinned wire (tined to prevent that outer layer from oxidizing and gaining resistance) that is braided into a flat strap, presumably because it is easier to run flat straps than thick cables. And if you look at the exposes surface area of a flat strap, versus a round cable? You get more surface area in the flat strap, too.

There are "skin effect depth" calculators on the web. For any given frequency (HF, VHF, UHF) you can actually calculate how deeply that RF frequency will travel in a conductor. If the RF only travels within 1/2mm or 1mm or the surface? Double that, for the two sides on a flat ribbon, and that's all the thickness you need. Anything more is just an expensive waste of copper, unless you are using it to carry DC or shunt lightning, or want the physical strength.

There really is old established science behind that stuff.
Copper braid is a poor RF conductor. It is like putting a resistor in series with the antenna. The transmitter RF energy is turned into heat and reduces the radiated power. But the VSWR will be nice and low.

What John recommended is what i would do. Live with what you have until you get some flat solid copper ribbon or foil. Then connect the tuner ground to a nearby through hull. Connect it to multiple through hulls if you can. The counterpoise is always a compromise and even really bad ones can be good enough. Even copper foil that just lies up against the hull connected to nothing is helping provide an RF path to the sea.
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