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Author Topic: Passing ground wire over gutters/siding and Connecting separate grounds  (Read 3313 times)
K0SDD
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Posts: 6




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« on: April 06, 2013, 02:03:57 PM »

I have a couple antennas attached to my chimney, I want to improve the grounding of the antenna masts, and follow best practice to tie this distant ground rod to my main ground system (electric service ground bonded to four additional rods to radios and antenna ground).

Grounding Masts and Connection to SVC/Shack Ground
I have bonded the masts together in the sense that mast A is connected via 6g to mast B, then to mast C, then to the ground rod. The two closest edges of the roof are 15' and 22' away (single story ranch). Each mast is only 2-3' from each other on the chimney. Option C is run the ground near my coax lines ~45' across the roof, then drop 20' down to rods/SVC ground.

 - 22' Ground - I am currently grounding the masts to a rod 22' away. This rod is not yet connected to my main service/shack ground. It would be fairly easy to run a 6g wire from this rod to the main rods, with two right angles….IF it is OK for me to pass the ground through my brick and cinderblock garage walls. This will require two right angles (and some bends around obstacle) to get to SVC ground, ~80' wire needed. The wire may pass over a conduit or two for garage lights.
 - 15' Ground - Grounding to the closest edge 15' away requires me to add a ground rod (no problem); and would probably be easier to run a 6g wire from this new rod to my station ground with one main right angle turn, with some bends here and there; ~65' wire needed.
 - 45' Ground - If I followed my coax direct back to the shack, across the surface of the roof, I would need ~70' of wire, with one right angle over the edge of the roof, no burying, no conduit, no drilling…the wire would lie near coax and LL, as this is the shortest path to the shack, but the longest to a ground rod

I appreciate any recommendations.

Over the Edge and Connection to Gutters/Siding
When putting the wire over the edge of the roof, my first preference was to screw it to the gutter, and then screw it under the eave, then run down the outside of the house (metal siding) screwing at corners until I reach my 8' ground rod (which is just outside of the roofline and closer to moister soil). But I want to avoid possible interference and risks of tying the lightening bolt to the siding and home.

I know I should avoid connecting to the gutter or siding and should be keeping my bends slow and 6-8" in diameter, so there is a single path to ground that won't touch other metal, etc. Right now I have just bent the wire to keep it elevated away from the gutter as the wire slowly curves to go straight down top the ground rod.

 - What do you recommend to help make that turn from the roof to vertical? Or to brace the wire from flopping around?
 - Does running wire with a jacket vs. bare make any difference?
 - What do you do for passing coax over the edge of the roof?
 - My wife would prefer the ground wire more hidden and against the metal siding, I am trying to do it in the best way possible.

In the past, for passing Coax over the edge of the roof, I have screwed a 12" x 4" piece of thin plywood just under the last row of shingles, so the ply hangs past the gutter. I then tied the coax to that ply via plastic ties and a 1/4" hole drilled in the ply. (The coax doesn't pass through the ply, the hole is for the ties.) I try to have a curve in the coax to help distance it from the gutter but think that is not so necessary (it is RG-213). I've thought of doing the same with plexiglass/Lexan, and make it 2-3' wide to allow for several coax or LL to be tied off.

My antennas are grounded via an MFJ Window Pass-through panel, to my service ground (4' below the pass-through). This main service ground has four additional rods bonded via 2" copper. Incoming phone and cable lines are tied to this service ground area as they attach to the house just above these rods

I appreciate any feedback, thanks!
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KØSDD-Stephen______________________________
Colorado Springs - Kenwood TS-830s/80m OCF/R-5
K7RNO
Member

Posts: 279




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« Reply #1 on: April 06, 2013, 03:16:35 PM »

Suggestion:

http://i43.photobucket.com/albums/e363/Sharpshooter1/HAM%20Radio/ground_zpsc3a26a24.jpg?t=1365286110

This is how I wired and routed my ground wire from a roof antenna. You can see how it runs along loose clamps just under the eaves' edge (screws there already existed, so wife is at peace).
Later, not visible in that image, it just drops down from the last clamp and goes loosely into the ground rod underneath it without being fixed against anything. If you need to run it along siding, you can use standoffs to keep it at a distance and prevent it from chafing along the siding in the wind.

In any event, insulated wire will prevent any rub-off of copper against siding or other surfaces.
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73,
aRNO
NAQCC #6870, SKCC #11131
KB4QAA
Member

Posts: 2371




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« Reply #2 on: April 07, 2013, 09:09:14 AM »

Ideally each mast should have it's own ground system.  However, with the mast 2-3ft apart I think it is acceptable to tie them together.

-The ground wire should run directly by the shortest path to ground.  There should be a ground rod at that point.

-The ground wire should not be connected to any other metal parts such as the rain gutters.  -

-Cables going over a roof edge should be supported at a point immediately above and below the edge, with a sufficient loop to prevent contact or rubbing.  You may use commercial TV twinlead supports, or bracket or fabricate them from aluminum or wood with appropriate cable clamps.

-One major purpose of grounding wires is to keep lightning outside the house.  Do not run ground wires into the house.   The electricians and engineers have indicated in discussions that it is permissible to run 'Bonding wires' between rods through the structure if it significantly shortens the run.

-Your plywood wire support at the roof edge sounds fine. No need to make extra work replacing it with plexiglass.  After all there is not need to insulate it.  The gentle curve sounds good, as does your service/shack ground!

Good questions, you are on the right path!  bill
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KV7W
Member

Posts: 136




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« Reply #3 on: April 10, 2013, 04:46:48 PM »

Here's a link with lots of good info about lookout tower, (fire watch), construction. There are a couple pdf's covering lighting protection. Take a look.

http://www.fs.fed.us/database/acad/lt/
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K0SDD
Member

Posts: 6




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« Reply #4 on: April 12, 2013, 04:00:09 PM »

Thanks for the feedback. I will let you know how it goes.
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KØSDD-Stephen______________________________
Colorado Springs - Kenwood TS-830s/80m OCF/R-5
K5LXP
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Posts: 4482


WWW

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« Reply #5 on: April 12, 2013, 04:43:31 PM »

NEC 810 answers all your questions.


Mark K5LXP
Albuquerque, NM
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KD8UXE
Member

Posts: 23




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« Reply #6 on: April 13, 2013, 06:57:28 AM »

I use number 4 solid copper for all of my ground wires harder to work with but very sturdy.
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retired United States Army Signal Corps 25c
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