This is an enduring myth, isn't it? What seems to
get neglected from the discussions is that
concrete is already a conductor, with or without
the rebar. One of the points of the Ufer ground
system is that the whole outer surface of the
concrete, wherever it touches the ground, is a
ground electrode, and the surface in contact with
the ground is measured in square feet, not square
As you said, Dave, where's the evidence for
lightning-induced explosions, or spalling, or any
of that, in a properly-constructed base? That's
why it was used to protect hundreds of tons of
munitions in lightning-prone Arizona Quonset huts
in WWII. Thanks. Mr. Ufer.
On 4/17/2011 2:00 PM,
> Message: 5
> Date: Sun, 17 Apr 2011 11:06:57 -0700
> From: David Gilbert<email@example.com>
> Subject: Re: [TowerTalk] grounding quesitons: Ufer, strap, exothermic
> To: firstname.lastname@example.org
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Again?? Seriously? That myth has been debunked so many times, both
> here and elsewhere, that I can't believe people are still perpetuating
> it. I've issued this challenge several times before and nobody has ever
> responded ... please quote one single URL or technical document that
> describes a verified instance where lighting passing through a proper
> Ufer ground , or any conductive element inside a buried concrete
> structure whatsoever, cracked the concrete. You'll find instances where
> a direct lightning hit to the OUTSIDE of a block of concrete caused
> damage (buildings, bridge abutments, etc), but not via a Ufer system of
> sufficient size and construction.
> Check out the I.C.E. technical note on the subject if you don't believe
> me. It's not difficult to find on their website ... it even uses the
> word "myth" in the subject title.
> Besides ... just think about it for a second. There are thousands of
> tower installations with a tower base buried in the concrete. What
> would be the difference, other than beneficial spreading of the current,
> if the tower was also properly connected to the rebar cage?
> Lastly, connecting the tower to the rebar cage is REQUIRED by most
> zoning regulations.
> I'm honestly curious why certain urban legends, like this one, seem to
> have such staying power in ham radio. I suspect it's because the
> purported consequences sound dramatic even if they happen to be totally
> unfounded. The more likely they are to fire up our emotional responses
> (fear, indignation, surprise, etc) the more likely they are to be
> believed ... and worse, passed on to others. Most of the stuff on
> Snopes is like that. If you want to create an immortal misconception,
> be outrageous about it.
> Dave AB7E
> On 4/17/2011 8:19 AM, Robert Harmon wrote:
>> Sounds like a very good ground system. I have a question on one thing.
>> As part of your grounding system you mention connecting to the rebar. I
>> assume this is the rebar cage that
>> will be cast in the concrete base. I think this is a no,no. A lightning
>> strike can
>> conduct thru the rebar and crack the concrete.
>> On Apr 17, 2011, at 7:24 AM, Mat Eshpeter wrote:
>>> I am about to pour concrete for the base of my HDX589 tower. I am going to
>>> go with a Ufer ground as well as the Polyphaser recommended eight 75'
>>> radials with multiple ground rods (8' rods every 16'). Location is on top
>>> of a 1600' ridge in WV and lightning is a very real concern. My QRZ web
>>> page gives a feel for the location.
>>> To build the Ufer ground, I am thinking about connecting a single bare 2/0
>>> stranded copper wire to the rebar. Questions:
>>> 1) is one enough?
>>> 2) how do I properly connect the copper to the rebar? Is exothermic weld
>>> the only way? Any problem with dissimilar metals?
>>> 3) how should the copper exit the base slab - above grade or below grade?
>>> Also, seems that copper strap is the preferred ground material for
>>> connecting rods together. Will 0.032" thick strap have significantly better
>>> longevity than 0.022" strap? I am refering to the strap sold by Georgia
>>> Copper. Copper is expensive and I don't want to invest in copper that
>>> won't add any value to my installation.
>>> Where can I find exothermic weld products to connect copper strap to 5/8"
>>> copper clad ground rods? I am exhausted reading Harger, Erico, Terraweld
>>> info, and can only find wire-to-ground rod products, no strap-to-rod
>>> TowerTalk mailing list
>> TowerTalk mailing list
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> End of TowerTalk Digest, Vol 100, Issue 37
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