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OT: Grounding Question

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Terry

OT: Grounding Question

I am building a new house. It has a UFER foundation ground. I will be putting ground rods around half the perimeter of the house between my shack and tower.

No. 4 solid copper wire will connect all my ground rods together and will tie to the UFER ground in two places.

I am having a sprinkler system installed and it would be possible to put my ground rods and connecting wire in the same trench next to the 1 in. Water line.

I live in an exposed area and my 35 ft. tower (which will have 3 ground rods around its base and radial ground wires) will be tied into the perimeter ground and UFER system as well; as will all my Elecraft station equipment.

If I get a lightning hit, will close proximity to my sprinkler lines destroy them? How far should my ground system be from m my main sprinkler system line if it is an issue?

Thanks!

73’s,

Terry de N7TB

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k6dgw

Re: OT: Grounding Question

Sounds like you're following the rules. You might consider flat copper
tape instead of wire for bonding. Lightning is an RF event and currents
will be confined to the outside surfaces of the conductors.
Consequently, the surface area rather than volume of the conductor is
what matters most. The conductors on one of the original transmission
lines from Hoover Dam to Los Angeles were hollow.

As to your last question, "it depends." There's no predicting what a
direct strike on your tower might do, the currents are so high that
everything in whatever path it chooses becomes a conductive plasma.
And, just because your tower is there does not mean all the strikes will
be direct. The W7RN contest station is on an exposed ridge at 6,500 ft
with multiple towers. As Tom points out, the lightning seems to choose
a sagebrush bush randomly more often than one of the towers.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 4/25/2018 9:41 AM, Terry Brown wrote:

> I am building a new house. It has a UFER foundation ground. I will be putting ground rods around half the perimeter of the house between my shack and tower.
>
> No. 4 solid copper wire will connect all my ground rods together and will tie to the UFER ground in two places.
>
> I am having a sprinkler system installed and it would be possible to put my ground rods and connecting wire in the same trench next to the 1 in. Water line.
>
> I live in an exposed area and my 35 ft. tower (which will have 3 ground rods around its base and radial ground wires) will be tied into the perimeter ground and UFER system as well; as will all my Elecraft station equipment.
>
> If I get a lightning hit, will close proximity to my sprinkler lines destroy them? How far should my ground system be from m my main sprinkler system line if it is an issue?
>
> Thanks!
>
> 73’s,
>
> Terry de N7TB
>
>
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>

ke9uw

Re: OT: Grounding Question

RF does not flow on the entire surface of flat copper tape (Electronic and Radio Engineering by Frederick E. Terman 4th Edition, p 22). The RF current only flows on the outside edges of the strip, not on the middle outside surfaces. Think of looking at the end of a longitudinal slice out of a solid copper rod.

Chuck KE9UW
[hidden email]

Sent from my iPad

> On Apr 25, 2018, at 12:32 PM, Fred Jensen <[hidden email]> wrote:
>
> Sounds like you're following the rules. You might consider flat copper tape instead of wire for bonding. Lightning is an RF event and currents will be confined to the outside surfaces of the conductors. Consequently, the surface area rather than volume of the conductor is what matters most. The conductors on one of the original transmission lines from Hoover Dam to Los Angeles were hollow.
>
> As to your last question, "it depends." There's no predicting what a direct strike on your tower might do, the currents are so high that everything in whatever path it chooses becomes a conductive plasma. And, just because your tower is there does not mean all the strikes will be direct. The W7RN contest station is on an exposed ridge at 6,500 ft with multiple towers. As Tom points out, the lightning seems to choose a sagebrush bush randomly more often than one of the towers.
>
> 73,
>
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
>
>
>> On 4/25/2018 9:41 AM, Terry Brown wrote:
>> I am building a new house. It has a UFER foundation ground. I will be putting ground rods around half the perimeter of the house between my shack and tower.
>>
>> No. 4 solid copper wire will connect all my ground rods together and will tie to the UFER ground in two places.
>>
>> I am having a sprinkler system installed and it would be possible to put my ground rods and connecting wire in the same trench next to the 1 in. Water line.
>>
>> I live in an exposed area and my 35 ft. tower (which will have 3 ground rods around its base and radial ground wires) will be tied into the perimeter ground and UFER system as well; as will all my Elecraft station equipment.
>>
>> If I get a lightning hit, will close proximity to my sprinkler lines destroy them? How far should my ground system be from m my main sprinkler system line if it is an issue?
>>
>> Thanks!
>>
>> 73’s,
>>
>> Terry de N7TB
>>
>>
>> ______________________________________________________________
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>>
>> --
>> This message has been scanned by E.F.A. Project and is believed to be clean.
>>
>>
>
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Chuck, KE9UW

Josh Fiden

Re: OT: Grounding Question

You're going to have to explain that to a whole lot of high current flat wound inductors & transformers.

What are you referencing? The only Terman I have handy is Radio Engineer's Handbook.

73
Josh W6XU

Sent from my mobile device

> On Apr 25, 2018, at 11:17 AM, hawley, charles j jr <[hidden email]> wrote:
>
> RF does not flow on the entire surface of flat copper tape (Electronic and Radio Engineering by Frederick E. Terman 4th Edition, p 22). The RF current only flows on the outside edges of the strip, not on the middle outside surfaces. Think of looking at the end of a longitudinal slice out of a solid copper rod.
>
> Chuck KE9UW
> [hidden email]
>
> Sent from my iPad
>
>> On Apr 25, 2018, at 12:32 PM, Fred Jensen <[hidden email]> wrote:
>>
>> Sounds like you're following the rules. You might consider flat copper tape instead of wire for bonding. Lightning is an RF event and currents will be confined to the outside surfaces of the conductors. Consequently, the surface area rather than volume of the conductor is what matters most. The conductors on one of the original transmission lines from Hoover Dam to Los Angeles were hollow.
>>
>>

ke9uw

Re: OT: Grounding Question

I gave the reference. 4th edition of Terman, Electronic and Radio Engineering. Page 22. The chapter on skin effect. The rf current is pushed to the outside edge of any conductor because the rf current is distributed in such a way as to make most of it flow where it is encircled by the smallest number of flux lines. And that’s the outside edge of any conductor. The rf current in the center obviously would be encircled the most. Terman gives a very clear description if you can source his text. He states that it is not the amount of conductor surface, but rather the way in which the conductor material is arranged. And I do realize that this is a very misunderstood subject. I’m not saying that flat ribbon doesn’t have skin effect, but just where the rf flows. Much of the outside surface in the middle of the ribbon has a high resistance to rf. So if you are using a ribbon of wire, it would have to be much larger than a round wire to have any advantage.
I have the Radio Engineers Handbook also and it does not have the same chapter on skin effect.

Chuck KE9UW
[hidden email]

Sent from my iPad

> On Apr 25, 2018, at 1:34 PM, Josh <[hidden email]> wrote:
>
> You're going to have to explain that to a whole lot of high current flat wound inductors & transformers.
>
> What are you referencing? The only Terman I have handy is Radio Engineer's Handbook.
>
> 73
> Josh W6XU
>
> Sent from my mobile device
>
>> On Apr 25, 2018, at 11:17 AM, hawley, charles j jr <[hidden email]> wrote:
>>
>> RF does not flow on the entire surface of flat copper tape (Electronic and Radio Engineering by Frederick E. Terman 4th Edition, p 22). The RF current only flows on the outside edges of the strip, not on the middle outside surfaces. Think of looking at the end of a longitudinal slice out of a solid copper rod.
>>
>> Chuck KE9UW
>> [hidden email]
>>
>> Sent from my iPad
>>
>>> On Apr 25, 2018, at 12:32 PM, Fred Jensen <[hidden email]> wrote:
>>>
>>> Sounds like you're following the rules. You might consider flat copper tape instead of wire for bonding. Lightning is an RF event and currents will be confined to the outside surfaces of the conductors. Consequently, the surface area rather than volume of the conductor is what matters most. The conductors on one of the original transmission lines from Hoover Dam to Los Angeles were hollow.
>>>
>>>
>

Chuck, KE9UW

Jef Allbright

Re: OT: Grounding Question

At very low frequencies, where the ratio of skin depth to conductor
thickness is significant, then the inductance from the flux within the flat
conductor will tend to confine current to the edges. In such a case, a
circular cross-section conductor will present less impedance.

The vast majority of the energy in a lightning strike is well below 1 MHz
and at 125 Hz the 100 effective skin depth is nearly a half inch.

As a practical example, following the R56 industry standard for grounding
and lightning protection for radio towers and their equipment shelters, you
will find a round, usually 2-gauge ground "halo" circling the walls at a
short distance from the ceiling. Strap is NOT used.

On the other hand, grounding at HF frequencies, where several skin depths
can be easily achieved with copper strap (0.005 inch at about 1 MHz) then
thin flat strap or hollow tubing is the way to go.

- Jef N5JEF

On Wed, Apr 25, 2018 at 12:27 PM, hawley, charles j jr <
[hidden email]> wrote:

> I gave the reference. 4th edition of Terman, Electronic and Radio
> Engineering. Page 22. The chapter on skin effect. The rf current is pushed
> to the outside edge of any conductor because the rf current is distributed
> in such a way as to make most of it flow where it is encircled by the
> smallest number of flux lines. And that’s the outside edge of any
> conductor. The rf current in the center obviously would be encircled the
> most. Terman gives a very clear description if you can source his text. He
> states that it is not the amount of conductor surface, but rather the way
> in which the conductor material is arranged. And I do realize that this is
> a very misunderstood subject. I’m not saying that flat ribbon doesn’t have
> skin effect, but just where the rf flows. Much of the outside surface in
> the middle of the ribbon has a high resistance to rf. So if you are using a
> ribbon of wire, it would have to be much larger than a round wire to have
> any advantage.
> I have the Radio Engineers Handbook also and it does not have the same
> chapter on skin effect.
>
> Chuck KE9UW
> [hidden email]
>
> Sent from my iPad
>
> > On Apr 25, 2018, at 1:34 PM, Josh <[hidden email]> wrote:
> >
> > You're going to have to explain that to a whole lot of high current flat
> wound inductors & transformers.
> >
> > What are you referencing? The only Terman I have handy is Radio
> Engineer's Handbook.
> >
> > 73
> > Josh W6XU
> >
> > Sent from my mobile device
> >
> >> On Apr 25, 2018, at 11:17 AM, hawley, charles j jr <
> [hidden email]> wrote:
> >>
> >> RF does not flow on the entire surface of flat copper tape (Electronic
> and Radio Engineering by Frederick E. Terman 4th Edition, p 22). The RF
> current only flows on the outside edges of the strip, not on the middle
> outside surfaces. Think of looking at the end of a longitudinal slice out
> of a solid copper rod.
> >>
> >> Chuck KE9UW
> >> [hidden email]
> >>
> >> Sent from my iPad
> >>
> >>> On Apr 25, 2018, at 12:32 PM, Fred Jensen <[hidden email]> wrote:
> >>>
> >>> Sounds like you're following the rules. You might consider flat
> copper tape instead of wire for bonding. Lightning is an RF event and
> currents will be confined to the outside surfaces of the conductors.
> Consequently, the surface area rather than volume of the conductor is what
> matters most. The conductors on one of the original transmission lines from
> Hoover Dam to Los Angeles were hollow.
> >>>
> >>>
> >
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

k6dgw

Re: OT: Grounding Question

In reply to this post by ke9uw

My apologies to all for inadvertently starting yet another pedantic
thread. When I still had a tower, copper was expensive [maybe still
is], and I could get about the same effective conductivity and cost with
1" copper ribbon as #4 solid wire, only the flat copper was quite a bit
longer which mattered. In any trade-off between engineering purity and
economics, economics always seems to speak at least as loud. And, had
my tower taken a direct hit, everything electric in the house would
likely have been gone, ground or no ground, and I'd need new
polyphasers. [:-) Again, I'm sorry, perhaps this can end quickly.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 4/25/2018 12:27 PM, hawley, charles j jr wrote:
> I gave the reference. 4th edition of Terman, Electronic and Radio Engineering. Page 22. The chapter on skin effect. The rf current is pushed to the outside edge of any conductor because the rf current is distributed in such a way as to make most of it flow where it is encircled by the smallest number of flux lines. And that’s the outside edge of any conductor. The rf current in the center obviously would be encircled the most. Terman gives a very clear description if you can source his text. He states that it is not the amount of conductor surface, but rather the way in which the conductor material is arranged. And I do realize that this is a very misunderstood subject. I’m not saying that flat ribbon doesn’t have skin effect, but just where the rf flows. Much of the outside surface in the middle of the ribbon has a high resistance to rf. So if you are using a ribbon of wire, it would have to be much larger than a round wire to have any advantage.
> I have the Radio Engineers Handbook also and it does not have the same chapter on skin effect.
>
> Chuck KE9UW
> [hidden email]
>

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Kidder, George

Re: OT: Grounding Question

In reply to this post by ke9uw

Does this imply that, for RF, the width of the strap is of minimal
importance, and that a 1/4 inch strap is almost as effective as a 1"
strap? It would certainly be less expensive!

George, W3HBM

On 4/25/2018 3:27 PM, hawley, charles j jr wrote:

> I gave the reference. 4th edition of Terman, Electronic and Radio Engineering. Page 22. The chapter on skin effect. The rf current is pushed to the outside edge of any conductor because the rf current is distributed in such a way as to make most of it flow where it is encircled by the smallest number of flux lines. And that’s the outside edge of any conductor. The rf current in the center obviously would be encircled the most. Terman gives a very clear description if you can source his text. He states that it is not the amount of conductor surface, but rather the way in which the conductor material is arranged. And I do realize that this is a very misunderstood subject. I’m not saying that flat ribbon doesn’t have skin effect, but just where the rf flows. Much of the outside surface in the middle of the ribbon has a high resistance to rf. So if you are using a ribbon of wire, it would have to be much larger than a round wire to have any advantage.
> I have the Radio Engineers Handbook also and it does not have the same chapter on skin effect.
>
> Chuck KE9UW
> [hidden email]
>
> Sent from my iPad
>
>> On Apr 25, 2018, at 1:34 PM, Josh <[hidden email]> wrote:
>>
>> You're going to have to explain that to a whole lot of high current flat wound inductors & transformers.
>>
>> What are you referencing? The only Terman I have handy is Radio Engineer's Handbook.
>>
>> 73
>> Josh W6XU
>>
>> Sent from my mobile device
>>
>>> On Apr 25, 2018, at 11:17 AM, hawley, charles j jr <[hidden email]> wrote:
>>>
>>> RF does not flow on the entire surface of flat copper tape (Electronic and Radio Engineering by Frederick E. Terman 4th Edition, p 22). The RF current only flows on the outside edges of the strip, not on the middle outside surfaces. Think of looking at the end of a longitudinal slice out of a solid copper rod.
>>>
>>> Chuck KE9UW
>>> [hidden email]
>>>
>>> Sent from my iPad
>>>
>>>> On Apr 25, 2018, at 12:32 PM, Fred Jensen <[hidden email]> wrote:
>>>>
>>>> Sounds like you're following the rules. You might consider flat copper tape instead of wire for bonding. Lightning is an RF event and currents will be confined to the outside surfaces of the conductors. Consequently, the surface area rather than volume of the conductor is what matters most. The conductors on one of the original transmission lines from Hoover Dam to Los Angeles were hollow.
>>>>
>>>>
>>
> ______________________________________________________________
> Elecraft mailing list
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>
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>

Jim Brown-10

Re: OT: Grounding Question

In reply to this post by Jef Allbright

On 4/25/2018 1:59 PM, Jef Allbright wrote:
> The vast majority of the energy in a lightning strike is well below 1 MHz
WRONG! Lightning is a VERY short rise-time impulse, so it is an RF
event, not a DC event. IEEE studies say that the energy in lightning is
VERY broadly centered (logarthimcally) roughly around 1 MHz.

73, Jim K9YC
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Don Wilhelm

Re: OT: Grounding Question

In reply to this post by Terry

Terry,

On your perimeter wire, remember that lightning likes to travel in a
straight line, so drive a ground rod at every point where the perimeter
wire makes a turn equal to or greater than 45 degrees. I would advise
you to run the wire all around the foundation perimeter.
The purpose of the perimeter wire is to provide a path for lightning so
it does not punch a hole in your foundation. The wire does not need to
be deep, its purpose is to spread the charge over as much of the earth
as possible.

I will let others expound on the Ufer ground - I have no comment.

73,
Don W3FPR

On 4/25/2018 12:41 PM, Terry Brown wrote:
> I am building a new house. It has a UFER foundation ground. I will be putting ground rods around half the perimeter of the house between my shack and tower.
>
> No. 4 solid copper wire will connect all my ground rods together and will tie to the UFER ground in two places.
>
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Wes Stewart-2

Re: OT: Grounding Question

In reply to this post by Josh Fiden

Radio Engineering and Radio Engineer's Handbook are two different critters. My
copy of Radio Engineering is the third edition and the pertinent information is
on p.20.

To partially quote: "Thus, with a flat-strip conductor, the current flows
primarily along the edges."

On 4/25/2018 11:34 AM, Josh wrote:

> You're going to have to explain that to a whole lot of high current flat wound inductors & transformers.
>
> What are you referencing? The only Terman I have handy is Radio Engineer's Handbook.
>
> 73
> Josh W6XU
>
> Sent from my mobile device
>
>> On Apr 25, 2018, at 11:17 AM, hawley, charles j jr <[hidden email]> wrote:
>>
>> RF does not flow on the entire surface of flat copper tape (Electronic and Radio Engineering by Frederick E. Terman 4th Edition, p 22). The RF current only flows on the outside edges of the strip, not on the middle outside surfaces. Think of looking at the end of a longitudinal slice out of a solid copper rod.
>>
>> Chuck KE9UW
>> [hidden email]
>>
>> Sent from my iPad
>>
>>> On Apr 25, 2018, at 12:32 PM, Fred Jensen <[hidden email]> wrote:
>>>
>>> Sounds like you're following the rules. You might consider flat copper tape instead of wire for bonding. Lightning is an RF event and currents will be confined to the outside surfaces of the conductors. Consequently, the surface area rather than volume of the conductor is what matters most. The conductors on one of the original transmission lines from Hoover Dam to Los Angeles were hollow.
>>>

donovanf

Re: OT: Grounding Question

In reply to this post by Kidder, George

The emails in this thread -- for the most part -- ignore the environment
surrounding the flat conductor carrying RF energy.

Flat conductors have much higher RF resistance in free space
compared to circular conductors of similar size. Big changes happen
when the environment is no longer in free space, such as those described
in this excellent EE Times article that describes the RF resistance of
flat conductors used in transmission lines and RF transformers:

https://www.eetimes.com/document.asp?doc_id=1278215

73
Frank
W3LPL

----- Original Message -----

From: "GWK" <[hidden email]>
To: [hidden email]
Sent: Wednesday, April 25, 2018 10:40:20 PM
Subject: Re: [Elecraft] OT: Grounding Question

Does this imply that, for RF, the width of the strap is of minimal
importance, and that a 1/4 inch strap is almost as effective as a 1"
strap? It would certainly be less expensive!

George, W3HBM

On 4/25/2018 3:27 PM, hawley, charles j jr wrote:

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donovanf

Re: OT: Grounding Question

In reply to this post by ke9uw

Fred's recommendation is exactly correct. Copper tape if far superior
to smaller diameter wire in buried lightning protection grounding
systems because it has much lower RF impedance to the surrounding
soil.

The RF resistivity of copper tape in free space has absolutely no
relationship to its performance in buried grounding systems.

73
Frank
W3LPL

----- Original Message -----

From: "charles j jr hawley" <[hidden email]>
To: "Fred Jensen" <[hidden email]>
Cc: [hidden email]
Sent: Wednesday, April 25, 2018 6:17:38 PM
Subject: Re: [Elecraft] OT: Grounding Question

RF does not flow on the entire surface of flat copper tape (Electronic and Radio Engineering by Frederick E. Terman 4th Edition, p 22). The RF current only flows on the outside edges of the strip, not on the middle outside surfaces. Think of looking at the end of a longitudinal slice out of a solid copper rod.

Chuck KE9UW
[hidden email]

Sent from my iPad

Jim Brown-10

Re: OT: Grounding Question

In reply to this post by Jim Brown-10

Thanks for this reference. K6STI sent me a comparable paper from NASA.
Note that the graph (which came direct but not on the reflector) is for
the radiated field, not the energy in the strike itself. My reference
for lightning spectrum is for the energy in a strike, and is from IEEE
Standards for power and grounding, which are published as "The Emerald
Book" and "The Green Book." It's been at least ten years since I read
it, and I don't recall in which book it is stated.

73, Jim K9YC

On 4/25/2018 5:17 PM, Jef Allbright wrote:

> On Wed, Apr 25, 2018 at 4:17 PM, Jim Brown<[hidden email]
> <mailto:[hidden email]>>wrote:
>
> On 4/25/2018 1:59 PM, Jef Allbright wrote:
>
> The vast majority of the energy in a lightning strike is well
> below 1 MHz
>
> WRONG! Lightning is a VERY short rise-time impulse, so it is an RF
> event, not a DC event.
>
>
>
> Jim -
>
> The energy from a lightning strike typically can be detected up to
> about 20 MHz but as you can see from Willett, 1990, the energy curve
> diminishes and /*is already down about -25dB before it reaches 1
> MHz*/. So the bulk of the energy is released well below 1 MHz. To
> provide equivalent energy above 1 MHz, you'd have to imagine the graph
> somehow suddenly leveling off and then continuing at that amplitude
> (25dB down) for nearly 500 MHz to provide a similar integral area.