On 3/26/2011 6:57 AM, Pete Smith wrote:
> 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,
That's pretty close to what I use. I use a bracket drilled for the
bulkhead connector fastened to the tower leg with a saddle clamp. The
problem with just clamping the bulkhead connector to the tower leg is
the only thing making connection is the U-bolt and the edge of the
PL-259s which are knurled which gives a low contact area.
The Times Wire approach does give a large surface area for contact both
at the coax and to the ground cable.
You could get more surface area by extending one side of the wrap/clamp
that goes around the coax braid so that it would fasten to the tower leg
the same as it fastens to the coax. It might take a bit more care in
water/weather proofing, but should give the best all around grounding.
At the bottom of the tower the coax could be grounded to the tower leg
in this manner with the ground cable attached at the same point against
the tower leg.
The only problem with this approach is the attention required to
weatherproofing. It sounds simple, but I see so many connections made
with inadequate, or improper weather proofing.
73
Roger (K8RI)
> 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¤t=Scotchmastic.jpg
>> ,
>> http://s83.photobucket.com/albums/j282/ersmar/?action=view¤t=Masticsealed.jpg
>> , and
>> http://s83.photobucket.com/albums/j282/ersmar/?action=view¤t=Scotch88.jpg
>> .
>>
>>
>> 73 de
>> Gene Smar AD3F
>>
>>
>> ----- Original Message -----
>> From: "K8RI on TT"<k8ri-on-towertalk@tm.net>
>> To:<towertalk@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@audiosystemsgroup.com>
>>>> Sent: Friday, March 25, 2011 10:00 AM
>>>> To:<towertalk@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@contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>>>
>>>>>
>>>>>
>>>>> -----
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>>>>>
>>>> _______________________________________________
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