Concrete isn't an insulator. It retains moisture which aids in
current flow.
The ARRL is incorrect in some of their statements.
PolyPhaser's efforts to have a dialogue about this
subject have been unsuccessful. If you understand
what's actually going on you'llrealize that the
LACK of a Ufer will cause the problems the ARRL fears.
The rebar of course shouldn't touch the J-bolts.
73, Bob Wanderer AA0CY
Sr. Appl. Engr.
PolyPhaser Corp.
----------
From: Len Schaier[SMTP:schaier@avotec.com]
Sent: Tuesday, September 23, 1997 4:23 PM
To: ku7y@sage.dri.edu
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Are "Ufer" grounding BEFORE pouring base cement?
Thanks Ron, right or wrong thats what I believe as well.
It may not be an accident that base drawings that I have seen seem to keep
the tower electrically separated from the rebar. I THINK the theory is that
one want to do ones best to keep current from away from the rebar because
1- concrete may not be that great an electrical conductor and
2-two unless you weld ( bad ) the rebar together you cannot be sure of the
current path to ground through the rebar (assuming one grounds the rebar).
For what its worth the 15 edition on the Antenna Handbook ( I need to buy a
new one ) says " The bars are positioned so that they will not contact an
metallic object in the base itself. This is done to minimize the possibility
of a direct discharge path for lightning through the base. Should discharge
occur, the concrete base would likely explode and bring about the collapse
of the tower."
Bottom line I believe is to keep the current from flowing in the rebar by
isolating it from the tower ( concrete is the insulator) and use ground
wires to connect the tower diectly to a good earth ground. Maybe a question
should be ..given that the direct ground fails, is it better to have a
ground through the rebar or no ground at all? In that case maybe a back up
through the rebar is better than nothing!!
Len
At 10:37 PM 9/22/97 -0700, you wrote:
>Hi Scott and all,
>
>Good question...one that I bet will have many answeres.
>
>I have been led to believe that one should always keep the rebar away
>from the tower. (Don't tie the bolts to the rebar or the rebar to the
>section of tower in the base).
>
>The thought was that the current would flow down the tower and then
>through the ground rods, leaving the base alone!
>
>That's the way mine is. Just sounds right to me!
>
>On the other hand, times change and we learn more..... :-)
>
>I'll be interested to see where this thread goes.
>--
>73, Ron
>
>NRA Life------Ex W6JXO, DL4RF, N7CRV------SOWP #5545-M
>QRP QRCI #8829----NorCal #330----QRP-L #17-----ARS #49
>AR QRP #150--------DM09cg---------New Washoe City, NV
>
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>
>
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