[Elecraft] OT: Grounding Question

Wed Apr 25 22:25:53 EDT 2018

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" <c-hawley at illinois.edu> 
To: "Fred Jensen" <k6dgw at foothill.net> 
Cc: elecraft at mailman.qth.net 
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 
c-hawley at illinois.edu 

Sent from my iPad 

> On Apr 25, 2018, at 12:32 PM, Fred Jensen <k6dgw at foothill.net> 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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