Ground options

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  • Updated 4 months ago
Not directly related to Flex, but close enough because I am a Flex user (sorry!).

I live in a 7th floor of a 13 stories high building (yes, all my antennas are up there) so I don’t have a proper by the book grounding system, actually I don’t have any ground at all. In the street level the building does not have any back or front yard (no yard at all) plus it has 2 underground parking lots...so no ground near.

What are my options for grounding?

Santiago
HI8SMX
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Santiago Mejia - HI8SMX

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  • curious

Posted 4 months ago

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Neil D Friedman N3DF

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As I understand your post, you have roof antennas above the 13th floor that are not grounded.  You may have lightning issues. 
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Santiago Mejia - HI8SMX

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Yes, that is correct. Luckily we don’t have too many lightning in my city, but yes that is a major risk at my station. But, there is no ground on the shack neither (7th floor), so it’s a double whammy.
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KC7ES

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You may be able to use the structural steel of the building as a ground for your antennas on the roof. Are there any cooling towers up there? You might find they have copper plumbing that may be useful. In your shack, there are products that create ‘artificial’ grounds.
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David Merchant

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I agree with KC7ES.  The structural steel of the building is the best way to ground. This is how commercial antenna structures are grounded in these environments.
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John KB4DU

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Are you looking for a lightning protection ground? If so, the building steel will be best. Most buildings this height have the building steel available at the roof for this purpose. For shack equipment, bonding together is the best you can do.
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KY6LA - Howard, Elmer

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I have lived in similar buildings (18th of a 25 floor and 19th Floor of a 30 floor building).  I have had great results using a MFJ-931 Artificial Ground which I highly recommend for such situations.  I gave away my last artificial ground to a local ham who lived on the second floor of a house.  He reports to me that it totally changed how his radio worked and made him finally able to work DX

Artificial Grounds tune out the reactance to ground so that you can maximize ground currents.
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WA2SQQ

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I believe that the "artificial ground" is aimed more at RF resonance matters. I doubt this device would offer any protection related to lightening or static buildup / discharge.
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Santiago Mejia - HI8SMX

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Yes, indeed. I'm in need of both.
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John

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There are two grounds in your shack you need to think about.  One is an electrical ground, like the grounding pin on your electric service.  Very old buildings did not have that but had copper plumbing or metal radiator pipes.  Your equipment should be grounded to those.  The other ground is for RF and any ground over a few feet away is useless, although the artificial ground box mentioned above can help tune it.  When I had lots of RF floating around my third-floor shack, I put copper screening under the carpet and attached the radios to that.  It is called a counter-poise and it worked pretty well.  Using a toroid on your coax cables, or a current-mode isolator, will prevent RF from running back and forth on your coax and help too.  It is not a science and takes one step at a time towards achieving a good ground at all frequencies when there is no earth to be had.  Resonant antennas with low SWR works best.  1/4 wave verticals not good.  Good luck.
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Martin Ewing AA6E

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Santiago -

I thought I had problems, with my shack on the 2nd floor of a 3 storey wood frame building! There is no obvious ground point here, except the AC electrical system. 

In your case, you should probably bond your antenna mast / tower / etc to the building steel using heavy (#6 AWG) cable.  You might ask for guidance from a local contractor that handles lightning protection systems.  It might be wise to install coax protective devices (like PolyPhaser) that would also bond to the building steel.

For RF, I would first try a common-mode choke in the coax line.  As others suggested, a tuned RF ground can help for reception.  Of course, that has to be retuned when you QSY.

Flex-wise, I have found that the SSDR noise blanking and wide-band noise filter have been really effective in my semi-industrial location.

73 Martin AA6E
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Santiago Mejia - HI8SMX

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Thanks everybody for all your comments, appreciate it. As for the roof, unfortunately the constructions (specially newer ones like mine) is mostly done thru concrete and the few metal infraestructures are well covered by concrete blocks and reinforced concrete, so no steel in the roof is easy to locate. 

In the shack, I will be testing the artificial ground and other measures. For example, I used a lot of chocks and ferrites in all cables (usb, power, coax, audio, etc..) and will look into the copper screening and see how that fits in my shack.

Following your advice, I ́ve also contacted a fellow ham and electrician, whose day job is installing radio stations antennas and equipments and we ́ll see my situation.

Again, thanks for the recommendations. All noted and all in my list.

Santiago