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Author Topic: Best RF Ground?  (Read 1117 times)
HFCRUSR
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Posts: 139




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« on: July 31, 2012, 02:52:30 PM »

Please let me give you all the setup first-
I live on the top floor of a 10-unit building. My SW antenna setup is right above my shack room on the roof at 40' up. I run a PAR EF-SWL to a 100' horizontal L wire (space limited up there-it does ok lol)
The feed end is mounted to a tripod with 5' mast, and one tripod leg is anchored to a solid copper aerator pipe, and a 7' length of #12 connects the joined PAR ground terminals to that pipe. The far end is tied to a plastic 4" insulator that is tied to an aerator pipe over there.
BTW, the last 50' of that 100' wire slopes about 10*
My main question here, is the ground to that aerator pipe safe for all in the building in a lightning event (will I or my neighbors get zapped at the sink?) and is my antenna truly "grounded" from that point up there, or is the pipe system acting as a giant counterpoise?
Thanks for any and all advice and tips.
I am under the assumption that I cannot run a long groundwire 40' to actual earth stake-or could a guy run one through aluminum conduit?
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WX7G
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« Reply #1 on: July 31, 2012, 03:14:45 PM »

Is the building safe in the event of lightning? I would say it is not.
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WB2WIK
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« Reply #2 on: July 31, 2012, 03:19:25 PM »

Please let me give you all the setup first-
I live on the top floor of a 10-unit building. My SW antenna setup is right above my shack room on the roof at 40' up. I run a PAR EF-SWL to a 100' horizontal L wire (space limited up there-it does ok lol)
The feed end is mounted to a tripod with 5' mast, and one tripod leg is anchored to a solid copper aerator pipe, and a 7' length of #12 connects the joined PAR ground terminals to that pipe. The far end is tied to a plastic 4" insulator that is tied to an aerator pipe over there.
BTW, the last 50' of that 100' wire slopes about 10*
My main question here, is the ground to that aerator pipe safe for all in the building in a lightning event (will I or my neighbors get zapped at the sink?) and is my antenna truly "grounded" from that point up there, or is the pipe system acting as a giant counterpoise?
Thanks for any and all advice and tips.

What's an aerator pipe?  I don't even know what one is, but if it's all copper it should be a good conductor.  Where's the other end go?

If you mean a "vent" pipe (to release steam and gasses from drains), those eventually reach the ground, but since they don't carry any pressure, they can be made from almost anything and could have interruptions.  Here at home, they are copper until they just exit the foundation where they immediately change to what was originally something like "clay" pipe, which I have upgraded to 6" PVC pipe, which goes all the way to the sewer line in the street.  As a result, I wouldn't rely on it being any kind of ground.

Is that what you meant?
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HFCRUSR
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Posts: 139




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« Reply #3 on: July 31, 2012, 03:58:37 PM »

Yeah that is it, vent pipe-sorry if I termed it wrongly. It kills noise from an avg s9 to +10 down to avg s6 and makes MW/LW very quiet. I am hoping to be able to keep it as ground to the antenna because I have no other way to ground it up here. I tried the fire escape system that is bolted to the steel beam frame of the building which did ok and also am grounded in here at the coax switch to the cold water feed of my bathroom next to the radio desk (about a 9' run) and need both grounds because with just one or the other I have more noise. I assume they work well together because they are at least close to the same potential?
There are power lines running not 20' from me here at eye level, and 10 cable tv runs pass right  over my shack room within 5' of my antenna feed and down the wall.
So WX7G and all, is this connection to that pipe a dangerous thing?

edit-better throw this in too-afraid to lay counterpoise wires for fear of them becoming tripwires to utilities workers up there...it's tough to do the right thing in my situation
« Last Edit: July 31, 2012, 04:13:49 PM by RXRXRX » Logged
HFCRUSR
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« Reply #4 on: July 31, 2012, 05:42:55 PM »

Anyone else?
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AA4PB
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« Reply #5 on: July 31, 2012, 05:53:06 PM »

The key question is whether that vent pipe is electrically connected to building steel. The building electrician can probably inspect it and tell you. Certainly nobody here can know if it is or not.
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HFCRUSR
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« Reply #6 on: July 31, 2012, 06:28:07 PM »

ok AA4PB I see. I know grounding is a touchy subject. But I really appreciate the help anyway.
I was wondering since my antenna wire runs close to the edge of the roof but is elevated about 8' off the roof, if running a counterpoise wire the same length underneath it and I could sort of embed it in the gravel up there-would that be a good noise canceller?
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K1CJS
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« Reply #7 on: August 01, 2012, 06:50:11 AM »

Some of those vent pipes are actually cast iron pipes that are connected right into the sanitary drain system, so they're actually a fair to middlin' ground.  In your case, that copper pipe is probably tied into the cast iron one--or the entire drain system (other than the water closet (toilet) drain(s) are made of copper   If your connection to that pipe drops your noise level that much, I would say that that is the case.  Since that pipe actually sticks out of the roof of the building, there should not be more of a risk of someone getting a zap from it--note I said 'should not be'--I did not say 'isn't'.
« Last Edit: August 01, 2012, 06:53:28 AM by K1CJS » Logged
KL3HY
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Posts: 117




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« Reply #8 on: August 01, 2012, 08:19:54 AM »

[...] and 10 cable tv runs pass right  over my shack room within 5' of my antenna feed and down the wall.

I'd be curious to see where those CATV drops are grounded to, and possibly try grounding to the same point.
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HFCRUSR
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Posts: 139




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« Reply #9 on: August 01, 2012, 02:26:31 PM »

K1CJS-
That's kinda what I thought, although I am "raising" the target up 8', which I don't think makes any difference to a bolt of lightning hi and duly noted on the risk-you can never pinpoint what ma nature's gonna do.

KL3HY-
those drops go down to a main box near the ground, then a single #8 runs out the bottom of their box to an electrical conduit protruding out the wall 1' from ground then going right into the ground (wonder what that's for) but this is about 45' down from my PAR. I was thinking of running a groundwire through condiut because I read somewhere they did this on ships from the radio room down to the hull (?) I guess this sort of prevents that wire from becomong part of the antenna. But I am at this point within the blessing of the building owner.. don't want to overbuild beyond what he approved. If I can keep this ground I will be thrilled-catching little thousand-watter BCs out of south America in 80 meters and such here/there is FUN! Thanks guys
« Last Edit: August 01, 2012, 02:28:30 PM by RXRXRX » Logged
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