[TowerTalk] Grounding Question

Gene Smar ersmar at verizon.net
Sat Mar 26 13:01:02 PDT 2011 

Pete:

     Electrically the method you describe is identical to mine and to 
commercial shield grounding kits.  However, mechanically your method uses a 
barrel connector plus two more PL-259s than the shield-only ground method, 
which can introduce additional points of failure in the coax subsystem.

     The bulkhead method could be used at the base of the tower where you're 
likely to have connectors anyway, like where you might connect the coax to 
Polyphasers protruding from a steel enclosure.  Connecting to these 
Polyphasers would provide the shield grounding we seek.  However, at the top 
of the tower it might be easier just to cut away the coax jacket and install 
the ground connector kit and weatherproofing material.


73 de
Gene Smar  AD3F


----- Original Message ----- 
From: "Pete Smith" <n4zr at contesting.com>
To: <towertalk at contesting.com>
Sent: Saturday, March 26, 2011 6:57 AM
Subject: Re: [TowerTalk] Grounding Question


> That Scotch mastic is interesting stuff.  What I don't understand is why
> people don't just use angle with bulkhead connectors, grounded through
> U-bolts to the tower legs, which in turn are grounded either through
> embedding in the base (self-supporting) or by short conductors to ground
> rods.  With appropriate attention to dissimilar metals issues, why
> wouldn't this be superior to separate copper conductors?  More diameter,
> more surface area, less to go wrong.
>
> 73, Pete N4ZR
>
> The World Contest Station Database, updated daily at 
> www.conteststations.com
> The Reverse Beacon Network at http://reversebeacon.net, blog at 
> reversebeacon.blogspot.com,
> spots at telnet.reversebeacon.net, port 7000
>
>
>
> On 3/25/2011 10:42 PM, Gene Smar wrote:
>> Roger:
>>
>>       I understand why you might think that weatherproofing a ground 
>> clamp on
>> braided coax like RG-8/u might be tricky.  However, it can be done if you
>> apply the proper materials.
>>
>>       I posted some time back in 2001 about applying homemade ground 
>> clamps
>> to my runs of RG-213 at the top and bottom of my tower:
>> http://lists.contesting.com/archives//html/Towertalk/2002-07/msg00698.html
>> .  You can see photos of how Joe KC2TN followed my suggestions here:
>> http://lists.contesting.com/archives//html/Towertalk/2007-10/msg00356.html
>> .  The trick to getting a proper seal is to use Scotch 2200 Mastic Pads 
>> to
>> cover the clamp and to bridge the cut in the coax shield.
>> http://s83.photobucket.com/albums/j282/ersmar/?action=view&current=Scotchmastic.jpg ,
>> http://s83.photobucket.com/albums/j282/ersmar/?action=view&current=Masticsealed.jpg
>> ,  and
>> http://s83.photobucket.com/albums/j282/ersmar/?action=view&current=Scotch88.jpg
>> .
>>
>>
>> 73 de
>> Gene Smar  AD3F
>>
>>
>> ----- Original Message -----
>> From: "K8RI on TT"<k8ri-on-towertalk at tm.net>
>> To:<towertalk at contesting.com>
>> Sent: Friday, March 25, 2011 10:01 PM
>> Subject: Re: [TowerTalk] Grounding Question
>>
>>
>>> On 3/25/2011 9:25 PM, Jim W7RY wrote:
>>>> If you would like to see how the professionals do it, take a look here:
>>>>
>>>> http://www.maplenet-inc.com/grounding
>>> I really dislike that approach on the types of cables most of us use. It
>>> works well with solid copper jackets like Heliax (TM), but I'd not want
>>> to use it with regular coax using either a braid or foil shield.  Also
>>> weather proofing these on braid and foil shields is much more critical
>>> than on a coax with a solid copper shield.  I much prefer the use of
>>> bulkhead connectors for those grounding points which I do at the top and
>>> bottom of the tower.
>>>
>>> I do use the ring around the base of the tower and tie that into ground
>>> runs going out to about 80' from the tower.
>>>
>>> 73
>>>
>>> Roger (K8RI)
>>>
>>>
>>>> Motorola's Communications Site Ground Standards know as R56, are all
>>>> written
>>>> around the NEC and TIA/EIA standards. As well as many MIL documents.  I
>>>> happen to work for one of the authors.
>>>>
>>>> W8JI has some good stuff on station grounding. www.w8ji.com
>>>>
>>>> Do some Google searching on Motorola R56 or tower site grounding or ham
>>>> station grounding etc. You will find lots of info.
>>>>
>>>> 73
>>>> Jim W7RY
>>>> Motorola
>>>>
>>>>
>>>> --------------------------------------------------
>>>> From: "Jim Brown"<jim at audiosystemsgroup.com>
>>>> Sent: Friday, March 25, 2011 10:00 AM
>>>> To:<towertalk at contesting.com>
>>>> Subject: Re: [TowerTalk] Grounding Question
>>>>
>>>>> On 3/25/2011 6:08 AM, Larry Libsch wrote:
>>>>>> I must be misunderstanding  something . How do I attach my
>>>>>> coax shield to the outside common point and also attach it to my 
>>>>>> radio
>>>>>> inside the shack?
>>>>> Since I wrote the grounding chapter for Steve's book, I'll attempt to
>>>>> clarify.
>>>>>
>>>>> One ancient and accepted method of accomplishing this is often called 
>>>>> a
>>>>> "ground window," where coax cables go through lightning arrestors
>>>>> (Polyphaser, ICE, etc.)  that are bonded to a conductive plate 
>>>>> (usually
>>>>> copper) where they enter the building, and that plate is bonded to the
>>>>> ground system.  The coax from the antenna has a PL259 that screws to 
>>>>> the
>>>>> arrestor on the outside of the wall and a coax jumper with PL259s on
>>>>> both ends goes between the arrestor and the radio.
>>>>>
>>>>> Several brands of arrestors are sold in "feed-through" form, so that 
>>>>> the
>>>>> plate can be installed in a wall (or an actual window). There's 
>>>>> nothing
>>>>> magic about the feedthrough arrangement, it's just a mechanically neat
>>>>> way to do it.
>>>>>
>>>>> The MOST critical part of all of this is the bonding together of ALL
>>>>> grounds associated with your home and shack -- power service entrance,
>>>>> shack, CATV, telco, other lightning arrestors, building structure, all
>>>>> ground rods, etc.
>>>>>
>>>>> 73, Jim Brown K9YC
>>>>>
>>>>> _______________________________________________
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> TowerTalk mailing list
>>>>> TowerTalk at contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>>>
>>>>>
>>>>>
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