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Does Paint Affect Braided Ground Line

Apr 25th 2012, 22:52

tas99

Joined: Feb 23rd 2012, 15:12
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I am planning on using 3/4" tinned braid for the ground connection from an antenna lightning arrestor to a buried copper rod; a distance of about 25'.

I was wondering if painting the braid will have any effect on its performance characteristic. Also, if I attach the braid with a screw through its center every 6 or 7 feet will that have any affect.

Any help would be appreciated.

Tom
Apr 26th 2012, 01:22

W1VT

Joined: Apr 4th 1998, 00:00
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Yes, you can paint a ground wire. You will need to remove the paint if you need to make an electrical connection.

I don't understand why you are putting screws through the braid every 6 or 7 feet. Could you explain what you are doing and why?

Zack Lau W1VT
ARRL Senior Lab Engineer
Apr 26th 2012, 02:00

tas99

Joined: Feb 23rd 2012, 15:12
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Zack,

Thanks for the response.

The reason for the screws is simply to secure the ground braid to the corner board of the house. It's coming from the roof to the ground rod below the corner board. Otherwise it would be just hanging free and subject to damage.

Thanks,

Tom
Apr 26th 2012, 10:42

W1VT

Joined: Apr 4th 1998, 00:00
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The only issue I can think of is galvanic corrosion--tin bolted to aluminum siding, for instance, may cause the aluminum to corrode quickly, if exposed to the weather. In this case a layer of paint between the two can be helpful.

Zack Lau W1VT
ARRL Senior Lab Engineer
Apr 26th 2012, 13:14

AA6E

Joined: Apr 4th 1998, 00:00
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I would hesitate to recommend braided wire (many small conductors) for outdoor ground applications. The conductors all get weathered after a while and make uncertain contact with each other. It becomes hard to solder when it is weathered, and there is a potential for rectifying junctions to form that lead to weird RFI problems. Lightning ground cables are typically have single conductors (like AWG #1/0) or heavy multiple conductors. Ground braids (even indoors) are questionable IMO. (So are arguments about skin effect!) The main advantage is flexibility. Somettimes people cite the required wire size in terms of weight -- how may pounds / 1000 ft. of copper. #1/0 is about 320 lbs/1000ft. In this view, it doesn't matter (much) whether it's in single or multiple strands. Unfortunately, weight = cost!

73 / GL
Martin AA6E
ARRL Technical Advisor
Apr 26th 2012, 18:03

tas99

Joined: Feb 23rd 2012, 15:12
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The issue of tin siding. It's actually wood siding and I'm securing it with screws to a wooden corner board. The paint is simply for looks.

As far as the comment on braid for ground. I choose that because of the recomendations of other guys and the staff at HRO. Now I'm concerned that I might not have made the right decision.

Thanks,

Tom
Apr 26th 2012, 18:34

WA0CBW

Joined: Apr 4th 1998, 00:00
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Braided ground wire is not allowed at most commercial 2-way radio sites. It has the potential to create intermod and has a higher impedance that solid copper, jacketed copper, or flat copper flashing. Motorola's R56 manual specifically prohibits braided ground wire either outside or inside radio sites. Either solid copper wire or jacketed copper wire should be used (sized for the appropriated distance).

BB
Apr 27th 2012, 01:22

AA6E

Joined: Apr 4th 1998, 00:00
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Tom,

Some grounding is better than no grounding, and few grounding schemes will fully protect you against a direct strike. The best grounding systems (IMO) use wide solid copper strap (2 inches or wider). That minimizes the inductance per foot -- important for the RF components of lightning current. But you still would like something like 1/3 of a pound of copper per foot.

Martin
Apr 27th 2012, 13:15

tas99

Joined: Feb 23rd 2012, 15:12
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Martin,

I guess I'll have to rethink my strategy and get away from the braid.

I understand the desireability of the wide copper strap but because of cost and the installation considerations it's not a good choice for me. The best alternative is #8 solid copper from the antenna to the ground rod.It doesn't come close to your recommended 1/3 of a pound per foot but it's a cost consideration.

Your opinion?

Tom
Apr 28th 2012, 02:35

AA6E

Joined: Apr 4th 1998, 00:00
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Tom,

It's always a compromise. A modest ground wire will help you in the case of near-by strikes, when you need to worry about induced currents in your antenna. Fortunately for all of us, near-by strikes are a lot more common than direct hits. (Especially if you're not the tallest structure in the area!)

Good luck.

Martin
Jun 20th 2012, 13:50

chanlesa

Joined: Apr 4th 1998, 00:00
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Hi,
I used to work for a federal agency that had lots of outside antennas, and they grounded all of their equipment buildings. The requirement for the antennas and the bldgs were different but they always used Thompson 32 4/0 copper ground braid,

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