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parallel grounds

Sep 24th 2011, 22:54

AD7XN

Joined: Oct 8th 2008, 15:07
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A couple of times in web discussions about station grounding I have read that you should run the antenna ground to the station ground. Is this a parallel ground that in many local codes is discouraged ?
Also should a connection be made between the electrical entrance ground and the station ground ?
Sep 25th 2011, 01:36

KM3F

Joined: Mar 6th 2008, 13:50
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Connect station and antenna grounds to the main AC entrance ground and to their own ground rods.
Look at other athorative sources of correct info and not depend on a discussion that may not be incorrect or you misunderstand what is being said.
Many get AC ground and RF grounding mixed togather as one and the same.
The main issue is lightining protection first, then any RF issues.
After all, antennas are sometimes very well liked by lightening discharges.
Other items are shock hazards with equipment that may have a defect making the metal structure hot.
Another way grounding is important is a lightening strike close by that induces power into the antenna and other metal structures through the earth or by direct coupling.
Strikes coming in on the power drop and telephone drop and TV cable drops all need to be addressed.
Sep 29th 2011, 15:23

AA6E

Joined: Apr 4th 1998, 00:00
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Assume here that we are talking about lightning protective grounds. For example, you could have a ground system at your antenna tower, another grounding arrangement for your station, and also an AC power ground for the house. Most references will tell you to "bond" all those grounds together. That means connecting them with a very stiff, low impedance connection. (Low impedance into the MHz range, because that's where a lot of lightning energy is.)

This is not easy to do, especially if there is physical separation between the tower, station, and AC power entrance. Keep in mind that if there is a lightning stroke to any part of your system (or nearby), there is going to be a lot of current flowing, when some pieces (like your antenna or tower) suddenly has a voltage surge of many kilovolts. You really want that current to flow in a short, heavy ground conductor, and not (for example) on your coax shields or other smaller wiring. You especially don't want it coming into your house.

Please check the ARRL Lab site on safety: http://www.arrl.org/safety .

73 Martin AA6E
Nov 8th 2011, 13:52

N0NB

Joined: Apr 4th 1998, 00:00
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The AC entrance should have a dedicated ground rod(s) per the NEC. The AC ground should then be bonded to the station ground--one does NOT want separate grounds on equipment which will happen if the AC ground and station ground are not bonded. Our company's standard is that the AC ground is bonded to the site ground with a removable clamp for ground system testing. Once the clamp is removed the AC entrance is still grounded for safety reasons.

According to my understanding of the NEC from my BICSI training, having the grounds bonded to each other does not constitute a parallel ground. Having them separate would, however, IMO.

The purpose of the AC ground is personnel safety and must never be compromised. The station ground provides an additional safety margin when bonded to the AC ground along with lightning protection and RFI suppression.

73, de Nate >>
N0NB.us
Dec 21st 2011, 02:16

ka1kpa

Joined: Mar 17th 2011, 16:56
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My station is on the 2nd floor I have 3 10 foot ground rods bonded but I am still getting rfi into my audio.Can you suggest improvement?
Dec 21st 2011, 16:33

WA0CBW

Joined: Apr 4th 1998, 00:00
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Setting up a station on the second floor or higher requires a different approach from a "grounding" standpoint. As the ground wire gets longer on its way to "ground" it begins to look more inductive. Depending on the type of antenna this can increase the chance of RF flowing on the outside of the coax bringing RF into the station. This can be minimized by using antennas that don't require grounds, such as dipoles. In addition chokes on the coax will also reduce the RF flowing on the outside of the coax. Using a balanced feed line such as ladder line or twin lead will also reduce the amount of RF getting into the shack. Be sure that both wires of the balanced feed line are carrying equal current. It may also be necessary to disconnect the "external" ground. In extreme instances isolating the safety ground may also be needed. Just remember to remove ALL other pieces of equipment or objects within arms length that may be connected to ground. Most important is to re-connect everything to ground before and during lightning producing storms. Or as I have found, move the station to the ground or basement floor if possible.

Bill
Dec 21st 2011, 21:42

ka1kpa

Joined: Mar 17th 2011, 16:56
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Total Posts: 0
Thanks Bill Merry Christmas & Happy New Year
Best 73

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