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Author Topic: Station Ground questions  (Read 3912 times)
AB1KC
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Posts: 46




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« on: November 07, 2011, 03:43:28 AM »

I know this subject has been hammered out many times but I am confused and need a bit of help.

My station ground is as follows:
  Station is located on outside wall of house directly above the electrical service.
  Electrical service is grounded to a ground rod via a twisted copper wire that I'm guessing is 6 gauge  wire.
  Station equipment is all grounded to a buss bar at the back of the operating desk. Each piece of gear has a connection via tinned 1" braid.
  Currently I have 1" braid connecting the buss bar to the "station ground". This is a 6' run of braid. The braid is covered with heat shrink as an attempt to weatherproof the braid.
  The coax entry point is a pair of holes through the wall.
  The coax ground point is a plate within a utility box with PolyPhaser surge protectors. This is mounted next to the entry holes about 1 foot away. This plate is grounded to the Radio station ground via the same braid. Coax leaves the utility box and comes into the shack via the two holes in the wall.
  I have begun using a SixPack antenna switch that is mounted outside to a galvanized water pipe driven into the earth  between the two ground rods. As of this morning I have not connected the SixPack to the ground system.
  The electrical service ground is connected to my shack ground with the same wire that connects the electrical panel to its ground rod.

OK, I've posted my setup and sins for all to see. Now help me get this right.

Here are my questions:
  1. Is it really necessary to use copper strap? Everywhere??? Getting from the station buss to whatever point I end up at is at best difficult without bending or kinking the strap. I am certain I can do it but is it necessary, will the braid work for this part?
  2. Reading W8JI's page on station grounding has me questioning the ground path I am using. It seems as though W8Ji says that I should run the connection from the station buss to the Coax ground/ polyphaser plate but not to the ground rod itself.
  3.  Where do I run the ground for the SixPack antenna switch?
  4. In looking at W8JI's page it seems as though he advocates connecting shack ac grounds to the station ground via strap. Am I misreading this? How does one pull this off exactly?

I am tired of RF issues in the shack and I want to just get the grounding part down pat before I move on into other areas.

73,
Bruce




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K3AN
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Posts: 787




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« Reply #1 on: November 07, 2011, 06:36:03 AM »

RF in the shack? What are the symptoms? What's the brand/model of your HF radio? Do you use a Heil headset? Are you using a linear amplifier? If so, does running barefoot eliminate the RF in the shack problem? Finally, what kind of antennas are you using?
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AB1KC
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Posts: 46




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« Reply #2 on: November 07, 2011, 07:15:07 AM »

Rf in the shack.
Well there is some RF in the shack but this is not the only goal here. I'm trying to "cover the bases" with good grounding practice before looking for the rf issues. If grounding fixes my issues great, but I'd like to know that the station is safe too. I am just not sure where to go with the grounding and this is a first step.

To answer your questions though Power makes the "RF" issue worse. It is seen in several ways in the shack on all antennas, a coax fed dipole for 80M, An OCF Dipole, a 5 band Yagi at 20M, a Vertical AV-18ht. No Heil headphones. I am now aware that the SixPack should have been grounded to the station somehow. Two radios that are used both exibit similar symptoms, One is a tenTec Omni VII the other is a Flex 5000a. Too many varied "symptoms" here to chase on this thread. Different bands, different antennas different symptoms.
73,
Bruce
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K9KJM
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Posts: 2415




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« Reply #3 on: November 07, 2011, 09:48:12 PM »

The setup you describe would have been a "dream" ground set up back in the 1950's and '60's.   However knowledge and techniques about good lightning protection has changed since then.
It has been learned that the fine wire "braid" type wire is far from the best conductor to use. (The only time it should really be used is where some flex is needed.  Like grounding a steel door to a steel door frame, etc.)  Flat copper strap is a much better conductor to use.  Even some low cost hollow copper tubing can work well if you are careful to not kink it.
The buss bar grounding to all pieces of equipment USED to be the way it was done.  Nowadays, The correct method is what is called the "Single Point" ground, For the ham shack the best location is usually near where the coax feed lines enter the shack.  That is the place to mount coax switches, Lightning arrestors, etc.  The best way to ground that (Some flat copper strap mounted to a piece of plywood makes a good single point ground panel.)  That panel should then be grounded outdoors to it's own ground rod(s) with a good low inductance conductor, Like the flat copper strap, Copper tube, Heavy wire, etc.   THEN all grounds are bonded together. (Your single point ground rods need to be bonded with power, Telco, Catv, etc grounds.)
The object of lightning protection grounding is to get the lightning to ground.   The single point ground panel concept works well.   I do not have any extra ground wires running to each piece of equipment.
I want the lightning getting to ground BEFORE it gets to my equipment.   My towers have taken many direct lightning strikes over the years with no damage to equipment.  The same can be said for commercial tower sites that are properly grounded and bonded.  (Of all the things you do to protect from lightning, Proper Bonding of grounds is the most important.  The "device" used, (Lightning arrestors) is close to the least important part of it. Contrary to popular opinion.)
Plus, Using the flat copper strap will provide the best RF ground. Installing counterpoise radial wires
(Which can just be a part of your ground rod installation) also works well for the RF ground. Ground rods really do little for the RF ground......  It is the bare copper radials that provide a good RF ground.
But usually if you have any RF in the shack problems, Grounding is just masking some other problem.
For tips on lightning protection grounding on a budget:
http://www.scribd.com/doc/14868226/lightning-protectiontaming-thors-thunderon-a-budget
Give that site plenty of time to load.
« Last Edit: November 07, 2011, 09:54:35 PM by K9KJM » Logged
WX7G
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Posts: 6039




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« Reply #4 on: November 08, 2011, 04:15:40 AM »

The preferred method is to run all antenna cables from the antennas to the house (building) AC power entrance and ground it there. Then route the cables to the shack. The shack should have no other paths to ground. If lightning hits there is no lightning current going to the shack.
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K1CJS
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« Reply #5 on: November 08, 2011, 12:19:17 PM »

Some people prefer to run all coax cables to the house ground--but it isn't necessary.  The most preferred method is to run all cables to outside the shack (or radio room, as the case may be) and install a ground bulkhead there.  Drive a ground rod into the soil at that bulkhead and connect the bulkhead to that ground rod.  Then using number 6 cable, bond that ground rod to the house mains ground rod AND any other tower or mast ground rods that you may have installed.

The purpose is to equalize the potential of ALL ground rods so there is no voltage differential between them from static discharge.  Also, the shorter the run of the coax cables for your station, the better the signal strength both receiving and transmitting, and the less there will be a chance of picking up noise on the extra lengths of coax.

Added--This won't address the problem of RF in the shack.  It is for lightning/safety grounding only.
« Last Edit: November 13, 2011, 02:19:24 AM by K1CJS » Logged
W0LEV
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Posts: 10




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« Reply #6 on: November 12, 2011, 10:51:37 AM »

If you are relying on your "ground" as a solution to "RF In the Shack", you're barking up the wrong tree.  The reason you have RF In the Shack is that the antenna is trying to find an "image" conductor - you have not supplied the WHOLE antenna.  The "antenna" is using the "ground" as a path for return currents.  In reality, a station need be grounded only for safety.  Relying on the "ground" for RF purposes is bogus and not founded in good antenna theory.  ARRL has promoted "grounding" to the point of ridiculousness.  Today, grounding should be considered ONLY for safety and lightning and not a solution to "RF In the Shack".  The "grounding" concept for RF In the Shack is left over from LONG AGO (spark days) when the ground system WAS part of the antenna.  Those were the days when we maximized RF current with an RF ammeter in the feed system instead of measuring SWR as a measure of good match to 50 +/- j0 Ohms.  With a good and properly installed antenna/feed, you SHOULD have lots of RF in the Shack, but it should not "bite" and cause other problems.  If the RF bites in the shack, look at your antenna/feed first and THEN the "ground" for safety and lightning remediation ONLY. 

I do not run a separate "ground" for my station as we live on granite - can't drive a rod (I do have an aggressive radial system under the vertical radiator I use on 160 and 80, however, which supplies an image plane for the radiating element).  On HF I generally use a 900' long doublet which sees the first low-frequency 1/2-wavelength resonance point just below the AM broadcast band.  I feed the antenna from the shack to the feed point with roughly 55' of parallel line and use a home brew differential-T matching network.  There isn't more than 10' of coax from the rigs through the amplifiers and ultimately to the 50-ohm common-mode current balun at the INPUT of the matching network.  I do not have RF In the Shack that bites on ANY band from 160 through 6-meters.  You shouldn't rely on a "ground" system as a solution to "RF In the Shack" in spite of what ARRL preaches. 

Dave - W0LEV
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WX7G
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« Reply #7 on: November 17, 2011, 08:57:28 AM »

Some people prefer to run all coax cables to the house ground--but it isn't necessary.  The most preferred method is to run all cables to outside the shack (or radio room, as the case may be) and install a ground bulkhead there.  Drive a ground rod into the soil at that bulkhead and connect the bulkhead to that ground rod.  Then using number 6 cable, bond that ground rod to the house mains ground rod AND any other tower or mast ground rods that you may have installed.

The purpose is to equalize the potential of ALL ground rods so there is no voltage differential between them from static discharge.  Also, the shorter the run of the coax cables for your station, the better the signal strength both receiving and transmitting, and the less there will be a chance of picking up noise on the extra lengths of coax.

Added--This won't address the problem of RF in the shack.  It is for lightning/safety grounding only.

With this method lightning current takes two paths to ground; To the bulkhead and through the AC wiring in the house to the AC service ground. If you want lightning current running through the house do it this way.

If you don't want lightning current running through the house do it this way: Run the antenna cables to the AC service ground first. Provide no other ground connected between the AC service ground and the shack. This provides no lightning path through the house AC wiring.
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K1CJS
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« Reply #8 on: November 17, 2011, 11:18:12 PM »

Lightning looks for the best, easiest path to ground.  Thinking that the resulting charge will go both ways is false.  Hams have been using the ground bonding arrangement with two ground points made common by a bonding link for years with no problems--and no "lightning" running inside the house.  Sorry, OM, but your thinking is wrong.

If you prefer doing the grounding your way, by all means go ahead.  Just don't promote the idea that your way is the only safe way.  It isn't--by far.

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AA4PB
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« Reply #9 on: November 18, 2011, 06:38:36 AM »

Ohms law is Ohm law. Electric current (from lightning or any other source) will divide and flow in both paths in accordance with their respective resistances. That's going to happen whether you ground your antenna cables at the electrical system ground first or not. Any time there are two paths to ground there is going to be some amount of current in each path.

My thinking is that normally the electrical system ground is not a particularly low impedance path given that it is usually a single ground rod that has been in place for years. You can usually do a much better job on your station ground by using several spaced ground rods. Much depends on the relative location of the electrical ground to the antenna cable entrance. I would NOT run an extra 100 feet of coax just so I could connect them to the electrical ground first. You are better off to ground the antenna cables right close to the entrance point. Then run a bonding wire on the outside (buried perhaps) between the antenna ground and the electrical system ground in order to meet the NEC requirements.

The bonding conductor between your station ground and the electrical system ground does not necessarily have to travel through the house. It actually should be outside. It is required by the NEC in order to ensure that all grounds are at the same relative potential. In fact, metal plumbing pipes are required to be bonded to the electrical system ground for the same reason. Think about the case where the grounds are not bonded together. Your power supply case is connected to the electrical system ground via the third pin on the plug. The radio case is connected to your antenna ground via the coax. The two grounds are at different potentials due to leakage in some of the home's electrical devices. You place one hand on the radio case and the other on the power supply case. Where can the current flow? From hand to hand through your heart! Have your ever seen sparks when connecting the coax to your radio? It's a sure sign that the bonding conductor is missing.

By the way, bonding simply means a permanent electrical connection. One that is never removed in the normal course of operation or service. No plugs or connectors that a user might disconnect.

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