Towertalk
[Top] [All Lists]

Re: [TowerTalk] Single Point Grounding question

To: "Roger \(K8RI\)" <K8RI-on-TowerTalk@tm.net>, "K1TTT" <K1TTT@ARRL.NET>
Subject: Re: [TowerTalk] Single Point Grounding question
From: "Bill Harris" <w7kxb@msn.com>
Date: Thu, 3 Sep 2009 16:53:05 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Roger:
I wonder if something like the Alpha Delta Transi-Trap Surge Protector 
installed at the base of the tower would have prevented the flash over? 
That's what I have but not up at the shack entry.
73
Bill Harris w7kxb
--------------------------------------------------
From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
Sent: Thursday, September 03, 2009 4:30 PM
To: "K1TTT" <K1TTT@ARRL.NET>
Cc: "'TowerTalk'" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Single Point Grounding question

>
>
> K1TTT wrote:
>> There will always be a potential difference between them during a 
>> lightning
>> stroke, you can't prevent that.  The concept of a spg is to protect
>> equipment in a building.  All the wires coming in through the spg are
>> connected together so they are all at the same potential so there should 
>> be
>> no chance for arcing and sparking inside the building.
>>
>
> Even that only sota, kinda, almost works.  All of my cables come in
> through a bulkhead.  The coax cable shields are grounded at the base of
> the tower AND they are grounded at the bulkhead along with the other
> coax cables,  rotator cables, remote antenna switch cables, where they
> come in the house. I've mentioned this before, but two of the cables are
> from the 144 and 440 arrays.  Both have pigtails that run from the
> bulkhead to the antenna selector switch.  I had one of them disconnected
> and laying on the desk about 8" to 10" from the switch. Lightning hit
> the tower and there was a tremendous flash from the coax laying on the
> desk to the selector switch. Yet both cables are the same length and run
> to the same grounding bulkhead.  Why the flash-over?  It sounded like
> some one fired a 12 gage here in the den. BTW both antennas are at DC
> ground.
>
> 73
>
> Roger (K8RI)
>
>
>> To confuse the issue a bit, a single installation may have multiple 
>> 'single
>> point grounds'.  Consider the case of a house with a separate garage that
>> has the radio shack in it.  There would most likely be a spg for the 
>> garage
>> so all the equipment in there is protected... and a separate one for the
>> house where the power, phone, catv, satellite tv, etc comes in to protect
>> all that stuff.  Thinking this way you could also create an spg for the
>> tower as a structure, bonding all cables at the bottom of the tower with
>> proper arresters, etc to protect everything on the tower... but this 
>> would
>> not substitute for an spg on the house.
>>
>>
>> David Robbins K1TTT
>> e-mail: mailto:k1ttt@arrl.net
>> web: http://www.k1ttt.net
>> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
>>
>>
>>
>>> -----Original Message-----
>>> From: Bill Harris [mailto:w7kxb@msn.com]
>>> Sent: Thursday, September 03, 2009 19:24
>>> To: TowerTalk
>>> Subject: [TowerTalk] Single Point Grounding question
>>>
>>> Hello radio fans:
>>> My question is:
>>> For lightning protection, the tower base is delta grounded. Coax, shield
>>> grounded at the antenna therefore, wouldn't the best place for SPG  be 
>>> at
>>> the tower base rather than the shack entry ?
>>>  I'm concerned about  about having difference in potential between two
>>> grounds.  Your input is most appreciated.
>>> Carry-on
>>> BillHarris w7kxb
>>>
>>> --------------------------------------------------
>>>
>>>
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>>
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
> 
_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk

<Prev in Thread] Current Thread [Next in Thread>