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Author Topic: Grounding Dilemma  (Read 448 times)

K1KIM

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Grounding Dilemma
« on: August 27, 2020, 01:35:46 PM »

The only available area for my shack is in the basement office. It is 270' from the vertical antenna. The only access to exit the house is 30 feet away from the office without tearing a lot of things up. And it's not a straight run.

I am running barefoot and always will be. This is the last shack I will be building. All the equipment I am currently running is hybrid except for a Kenwood 430. Not including the
2M and 70cm radios that are mobils  of 1/25W off a power supply.

Can I / Should I just leave the equipment grounding to the 3rd ground pin or find another way? All the power cords have been converted to 3 prong with the ground wire going to the chassis ground lug on the radio. The service panel for the house is 90' away on the otherside of the house.

The antenna coax shielding is grounded and there are Polyphase lightening dumps before entering the house.

I have walked the basement and outside 100 times trying to figure this out!

Side Note..... I have read the ARRL book on grounding, but can't seem to figure this one out.
« Last Edit: August 27, 2020, 01:40:53 PM by KE8BFN »
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KB7TT

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Re: Grounding Dilemma
« Reply #1 on: August 27, 2020, 02:17:03 PM »

Well, the third wire ground is just an AC ground, not really an RF ground.  Having said that it is much better than nothing.  Having said that and understanding your challenge the only thing I can suggest is "what about a tuned 1/4 wave wire running somewhere in the basement.  That would bive you effectively an RF ground.  Insulated wire is recommended to prevent shocks to humans or furry persons when transmitting.  1/4 wave wire on the band(s) of operation is quite effective to keep rf out of the shack and provide an artificial ground.... Been there, done that.  It works.

Gud luck

Greg
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K6AER

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Re: Grounding Dilemma
« Reply #2 on: August 27, 2020, 02:21:23 PM »

More than 90% of lightning damage comes in via the main AC feed. The first thing you can do to mitigate surge damage is to put a commercial surge protector in you circuit breaker panel. The surge protector cost about $100 at Lowes or Home Depot. They install with two black wire for each split phase and a white and green wire to the panel ground. Each phase is connected through a 20-amp breaker to the panel AC.

The next bit of work is to make sure the ground rod for the panel is adequate.  You can rent a ground impedance meter like an AEMC unit to test the ground impedance. The minimum is less than 10 ohms. If your impedance is more then ten ohms you need to add another ground rod at least ten feet away from the existing unit. Deeper ground rods are better then lots of short ones. The goal here is to by pass the lightning energy to earth. Keeping your equipment out of the surge path is the task.

Most hams spend a lot of energy making the antenna ground the best in the world. Not the AC entrance panel. As a result, when an AC surge comes in from the main feed the best ground is the ham antenna installation. As a result, your ham equipment in between becomes a fuse.

As far as lightning RF surge protectors are concerned, they take up to 10uS to for the gas protection tube, in the protector, to fire. Up to that moment the full voltage of the antenna surge can be placed on the input of your equipment. Remember the voltage is trying to get to earth ground. The best protection is to use a grounded antenna switch to ground the center conductor to hard ground. This also includes any other lines coming into the shack including any copper lines such as cable, phone and anything else.

Don’t worry about being on the air in a thunder storm. You should be off the air then. Also, I have a main AC disconnect for when I am not in the shack. Just a bit more protection from lightning surges.

One last item is to make sure all grounds are bonded with at least a number 8 Gage wire to your main ground system.

Best of luck,

Mike
« Last Edit: August 27, 2020, 02:34:02 PM by K6AER »
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K1KIM

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Re: Grounding Dilemma
« Reply #3 on: August 27, 2020, 02:42:32 PM »

The best protection is to use a grounded antenna switch to ground the center conductor to hard ground. This also includes any other line coming into the shack including any copper lines such as cable, phone and anything else.

My antenna switch grounds the center conductor to the shielding when I switch the radio to the dummy load, which I do whenever not in use. Theshielding is of course connected to the radio chassis and earth ground before coming inside.

The surge protector and existing service panel ground rod are good suggestions.


One last item is to make sure all grounds are bonded with at least a number 8 Gage wire to your main ground system.

I can bond the antenna tuner, etc to each other, but then they have no ground other than the wall outlet 3rd prong and the coax shielding grounded outside. The chassis will not have it's own separate ground.

« Last Edit: August 27, 2020, 02:47:40 PM by KE8BFN »
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W9IQ

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Re: Grounding Dilemma
« Reply #4 on: August 27, 2020, 03:19:47 PM »

There is no reason to have an RF ground in your basement shack. In fact, you cannot even reasonably achieve that. If you are getting common mode current in your shack, simply use choking baluns on your coax before it enters the house and near the antenna.

Your Polyphasors on the outside provides sufficient surge protection for static drain and near lightning hits. Make sure that the antenna surge ground system is bonded to your house ground system.

For your basement shack equipment simply tie all equipment grounds to your house wiring ground at the outlets for the shack. If you can disconnect all exterior coax when your shack is not in use, all the better.

- Glenn W9IQ
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God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

KD6VXI

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Re: Grounding Dilemma
« Reply #5 on: August 27, 2020, 05:01:27 PM »

There is no such thing as an RF ground.  I've said it before, and I'll say it again.  There is no such thing as an rf ground.

RF is expensive to make.  Why are you wanting to dump some of it into the ground.

A ground for your radios is for lightning and shock protection.  Nothing else. That's it!

You need to run a piece of wire from your station ground buss to the service panel.  The size of that wire depends on your main breaker, according to NEC.

At the minimum you need to have a pair of ground rods, spaced the length of the ground rods.  Those need to have a wire sized at least number 8 (number six is the lowest we can use in my jurisdiction), armored at the minimum (or large enough to prevent damage (like number two)) , solid preferable.

You use the dame size wire to your station ground buss.  Then bond each piece of equip to the station ground buss.  You can also bond each piece together.

The point of all this is to keep your station at the same voltage level during a lightning stroke.

Dumping rf into the earth is bass ackwards.  Chokes at the feed point of the antenna and where your feedline come into the building are what you want.  This keeps rf inside the coax, and noise outside of it.

--Shane
KD6VXI
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K1KIM

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Re: Grounding Dilemma
« Reply #6 on: August 27, 2020, 05:13:17 PM »

Shane
As I said above. I cannot run any connection to my service panel ground. Not possible.
The only connection to ground I have is the 3rd prong of the AC receptacle that goes back to the panel as every out with 14awg.
With all the equipment bonded to a single point, I still only have the coax shield from the chassis' to the Polyphase body which is to earth ground. That and my power plug ground to chassis are the only AC grounds I have.

If you are getting common mode current in your shack, simply use choking baluns on your coax before it enters the house and near the antenna.

Glenn
I do have a choke outside my radial field and several loops of coax before it enters the house.

Make sure that the antenna surge ground system is bonded to your house ground system.


The antenna is nowhere near that side of the house to tie into the panel ground. All I can do is drive new rods by the Polyphasers before they enter.
« Last Edit: August 27, 2020, 05:30:06 PM by KE8BFN »
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N9LCD

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Re: Grounding Dilemma
« Reply #7 on: August 27, 2020, 06:40:50 PM »

KE8BFN:

I had the same problem at my QTH.

If I had followed the recommendation -- and it is a recommendation -- to ground everything at the service panel entrance, I would have had to run a broad copper band from the chimney where the antenna "farm" would; down the side of the house; around the back, obstructing two entrances; and finally to the service panel entrance point.

About 65 FEET of copper band / strip!!

Around two aluminum downspouts.

Around an aluminum sided wooden porch.

And cut a hole in the decorative brick wall serving as our fence.

"Do as much of the recommendations as you can, as well as you can and don't get carried away."  That's the advice I received & I pass it on.

As for the proposed antenna farm, I scrapped it.  Our masonry contractor said that our chimney was structurally sound for most 607-land weather but the "antenna farm" and an unusual wind storm could damage the chimney.

IMO.  No antenna is better than no heat. ???
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W9IQ

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Re: Grounding Dilemma
« Reply #8 on: August 28, 2020, 05:01:25 AM »


Make sure that the antenna surge ground system is bonded to your house ground system.


The antenna is nowhere near that side of the house to tie into the panel ground. All I can do is drive new rods by the Polyphasers before they enter.

Then consider running the bonding wire through the house if there is no other route. The NEC permits this type of construction.

If you don't bond the two ground systems to near equipotential, any lightning currents can pass through your station on the way to the other ground system. This will turn your nice basement station into a blown fuse. The other possibility is that if the house ground rod system becomes disconnected or goes high impedance, all household fault currents will start passing to the other ground system via your station. Not a good situation and potentially (pun intended), a lethal one. So get your ground systems bonded together with heavy wire, 8 gauge or larger.

- Glenn W9IQ
« Last Edit: August 28, 2020, 05:08:24 AM by W9IQ »
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W1VT

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Re: Grounding Dilemma
« Reply #9 on: August 28, 2020, 05:07:55 AM »

I read in the newspaper about a ham in Glastonbury CT losing his home because the ground systems weren't connected.  Fortunately he was vacationing on the Cape when it happened.

Zak W1VT
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K1KIM

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Re: Grounding Dilemma
« Reply #10 on: August 28, 2020, 07:37:00 AM »

If you don't bond the two ground systems to near equipotential, any lightning currents can pass through your station on the way to the other ground system.

Glenn,
In the above situation where would the lightening currents originate then? If at the antenna would'nt the Polyphase or any arrestor dump that current to the outside ground rods (not AC panel rod) before entering the shack traveling through the radio chassis ground and back to the house AC panel via the outlet ground lug? Are speaking about point of oringin at the panel?

Correct me if wrong but isn't the equipment bonded to the AC panel ground rod by just plugging in the 3prong plug? I realize that the 14 awg will vaporize this way, so thusly an inadequate ground for that side of the grounding in the event of that much energy passing to earth.
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W9IQ

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Re: Grounding Dilemma
« Reply #11 on: August 28, 2020, 08:09:42 AM »

It is often tempting to think that a few ground rods (ground electrodes in NEC parlance) can simply absorb all the energy of a lightning strike. But this is far from reality - each rod experiences "ground saturation". So while your grounded Polyphaser will hopefully direct a great deal of the lightning energy to its local ground rods, there will still be ample energy looking for alternative routes to ground that isn't saturated. The same is true for lightning coming in via your service connection, telephone line, satellite dish, CATV line, etc.

Large, commercial tower operations have an extensive grounding system network with many ground rods, radials and a grounding ring at the base of the tower to help distribute and absorb most of the lightning energy. Because it is well distributed, it does not reach ground saturation as easily during a lightning event. The result is that this will greatly reduce, but not completely eliminate, the amount that must be dealt within transmissions lines, the building and the communications equipment.

- Glenn W9IQ
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God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

K1KIM

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Re: Grounding Dilemma
« Reply #12 on: August 28, 2020, 08:32:36 AM »

I can then eliminate this problem by disconnecting the equipment from their power source and antenna connections except when in use (not in potential storm/lightening activity).

A PITA but perhaps my only solution to get on the air safely right now. My vertical is set in a copse of trees that are 100'+ tall. The antenna is 25'. I don't know if that will work in my favor or not. ::)
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W9IQ

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Re: Grounding Dilemma
« Reply #13 on: August 28, 2020, 08:39:15 AM »

I can then eliminate this problem by disconnecting the equipment from their power source and antenna connections except when in use (not in potential storm/lightening activity).

I don't agree. Can you not bond the ground systems together via a wire run within the house?

At the very least, consider what will happen if the impedance of your household ground electrode is higher than that of your antenna ground electrode - your station is the bridging conductor for any fault current. Imagine what happens if you per chance are disconnecting your PL-259 at that moment...

Regarding trees and lightning, let me give you my experience from last year. We had a large black walnut tree on the ranch take what looked like a direct strike. The bark was blown off the entire trunk. In that area, I had fence wire tied between 4.5 inch steel posts sunk 5 feet into the ground. All of this fence wire was completely destroyed as the lightning energy sought out non-saturated ground. The fence wires simply could not support the current that was involved. I even found some fence wires nearly a quarter mile away that were melted. Don't underestimate the effect of a lightning hit.

My large fence charger was not at all bothered by that hit. But I had put in an extensive lightning ground system and impedance retardation on the charger feed for this exact scenario. It did its job.

- Glenn W9IQ

« Last Edit: August 28, 2020, 08:46:50 AM by W9IQ »
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VK5ISO

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Re: Grounding Dilemma
« Reply #14 on: August 29, 2020, 12:25:42 AM »

Sometimes it helps to think out of the box: the biggest issue with lightning, as has been correctly pointed out is a surge on the power line.

 Your antenna should be well-grounded and disconnected except when you are using the station (and no sane person uses a transceiver during a storm). I use Polyphasers throughout, but would never trust them to stop a direct lightning hit: the antenna should be disconnected at the base of the mast (and not in the shack!), if you really want to play it safe.

As to power supply, why don't you simply run your station off a bank of 12v batteries (I use  an 100AH LiFePO4 but lead-acid is the time honored solution)? I have been charging my battery with a dedicated charger, but am in the process of installing a high-end Silentwind wind generator. Charge the batteries, disconnect and use. Bis repetita!

Your station will be fully protected and the only components exposed to a possible surge would be the battery bank during charge.

Then, if lightning strikes your antenna out of the blue while you are operating, that is what is still know in insurance as an "act of God" and nothing can be done.

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