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Author Topic: Earth Grounding  (Read 262 times)
N4ZW
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Posts: 21




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« on: June 17, 2004, 11:37:53 AM »

I live on the 9th (top) floor of an assisted living community which I administer. I just installed a 4 el SteppIR on the roof approximately 25' above the flat, asphalt/gravel roof.  I need to ground my equipment (FT 1000D, amp, etc., etc.).  There is a cold water pipe available that connects to the main run throughout the building about 10-12' away.  Any thoughts from experience?
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K5DVW
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« Reply #1 on: June 17, 2004, 11:49:20 AM »

Why do you need to ground your equipment? Your antenna is a balanced antenna, so you dont need an RF ground. I'm sure your equipment is plugged into the wall via an AC power supply, so you have safety ground that way. The only ground left is a lightning ground, and that should be taken care of ON THE ROOF not in the shack. Altho, I'd hate to tie into the buildings lightning system due to the liability involved. Maybe someone else knows something about that.
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K6AER
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« Reply #2 on: June 17, 2004, 12:48:40 PM »

The problem with grounding on a roof top is providing a lightning path to earth ground with such a long run. Several items need to be addressed. Surge protection for the RF cables, surge protection of the rotor lines and surge protection for the Stepper controller wires will be needed. Also your rotor and stepper controller box should be grounded at the station along with all radio equipment.

Both the rotor and stepper lines are less than 35 volts AC. A MOV type of surge protector will provide good protection but a Silicon Avalanche Diode surge protector from Citel is much faster. The RF lines will need a gas tube surge protector rated for the highest wattage that you will use.  You will need to set up a surge protection demarcation point at the roof top and tie into the building lightning ground system. This will be the lowest impedance path to earth ground. Do not use the electrical ground in your apartment. The conductor size is rated only for electrical ground loop and NEC purposes and will not provide low enough impedance for lightning applications.  

The application of lightning protection in an apartment and residential application is a bit different than a commercial application. You have to treat the lightning surge not only as a DC potential but you have to address the RF component of lightning as well. Long ground leads will look like a high impedance connection at resonate frequencies.

There is not enough time and space to go into all the aspects of what you need to do but I will send you a white paper I wrote for Nextek at Dayton which cover what all needs to be done in a typical SteppIR installation.

Good Luck.

73’s – Mike, K6AER
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WB2WIK
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« Reply #3 on: June 17, 2004, 01:11:48 PM »

Surely if you're looking for a lightning return path, you wouldn't want it to be via your equipment, or run through the building.  That should be entirely located *outside* the building, with a big, fat cable going from your antenna support structure to earth, via a path that has lower impedance than the cables routing to your station, otherwise you'll have no protection to speak of.

WB2WIK/6

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AA4PB
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« Reply #4 on: June 17, 2004, 02:01:12 PM »

Many large buildings already have some sort of lightning protection ground available on the roof. You can ground your mast to that. Are there any lightning rods, other antennas, large HVAC units, etc on the roof that may have a large grounding cable attached?
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N4ZW
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« Reply #5 on: June 17, 2004, 03:47:59 PM »

Thanks, guys, I guess the antenna issue threw everyone's thinking off to the lightening angle.  My issue is equipment grounding.  I want to ground the txcvr, amp, and the peripherials via a common bus.  Yes, the antenna is less than 1.2:1 SWR but I would feel better and hopefully would reduce noise by a good ground.  The waterpipe mentioned in my last post is the nearest thing I can reasonable think of.  Thoughts?  And many, many sincere thanks for all the answers.  I have grounded the antenna to the building lightening system via a 4" wide solid copper strip and will install arrestors and surge protectors shortly.
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AA4PB
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« Reply #6 on: June 17, 2004, 04:20:06 PM »

With a balanced antenna like you have the only two grounding issues are lightning (which you have) and an electrical safety ground (which you probably have as the third pin on your power plug). The safety ground MUST be tied to the building electrical system.

You have no need for an RF ground at the radio with a balanced antenna system and I doubt that adding one will reduce noise pick up any. It shouldn't hurt to ground the rig case to the water pipe but I doubt that it will provide any real benefit if your antenna system is working correctly.

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WB2WIK
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« Reply #7 on: June 17, 2004, 04:25:53 PM »

I've never once seen a station ground have any influence on "noise."  There's no technical reason that it should, and it doesn't.

I'd say feel free to connect to the water pipe, it shouldn't hurt, although it shouldn't help, either.

"Station grounding" is something that is evidently much misunderstood.  When using matched antennas, there's nothing served by a station ground.  An RF ground can help in certain situations, but on the 9th floor of a building, you can't achieve an RF ground, at least not an "earthed" one.  With a beam such as the SteppIR, I wouldn't give any thought to a station ground at all.

In 39 years of hamming from dozens of locations including fifteen houses I've owned and lived in, running high power on many bands from all, I've never had any sort of station ground and can't think of any reason to have one.

The safety ground provided by the utility mains ground wire is sufficient to protect against shock hazard in the event of equipment internal short-circuit.

WB2WIK/6
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N6AJR
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« Reply #8 on: June 17, 2004, 05:13:40 PM »

you could make some quarter wave counterpoise's ( same as a 1/4 ~ radial) and hook to your common ground point on the transciever.  this can be done with a piece of 3 or 5 wire rotor cable from radio shack, and cut each wire in the cable to a specific quarter wave  and it will mofe and tendencies to have a "hot mike" ayaw fro the rig. A counterpoise is a cheep and great "artificial" ground for a rig.  or make them out of 16 or 18 guage  insulated hook up wire.  tape the far ends a the voltages get amazing there
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N6AJR
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Posts: 9915




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« Reply #9 on: June 17, 2004, 05:21:42 PM »

   try this again.. oops


You could make some quarter wave counterpoise's ( same as a 1/4 ~ radial) and hook to your common ground point on the transciever. This can be done with a piece of 3 or 5 wire rotor cable from radio shack, and cut each wire in the cable to a specific quarter wave and it will move any tendencies to have a "hot mike" away from the rig.

A counterpoise is a cheep and great "artificial" ground for a rig. or make them out of 16 or 18 guage insulated hook up wire. Tape the far ends as the voltages get amazing there !!
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