[TowerTalk] Lightning Protection Question

[Roger (K8RI)]

On 9/11/2010 9:28 PM, Gene Smar wrote:
> TT:
>
>       I re-read this and my earlier post.  It may not be clear that the
> Polyphasers to which I am referring are on the ANTENNA side of the remote
> switch, not on the shack side.  Hope this clarifies what I have at the base
> of the tower.
But this still raises the question of "why".
As most one here have agreed the inactive ports on the switch should be 
grounded.  That is even better than a lightning arrestor and only takes 
a few minutes to add to those switches that do not have it.

You have the difference between about 15 minutes and 10 cents worth of 
solder to insure a grounded coax, versus about $250 dollars worth of 
arrestors.

73

Roger (K8RI)
>
> 73 de
> Gene Smar  AD3F
>
>
> ----- Original Message -----
> From: "Gene Smar"<ersmar at verizon.net>
> To: "Jim Brown"<jim at audiosystemsgroup.com>;<towertalk at contesting.com>
> Sent: Saturday, September 11, 2010 8:36 PM
> Subject: Re: [TowerTalk] Lightning Protection Question
>
>
>> Jim:
>>
>>      You overlooked my caveat in my original e-mail:  I have a remote
>> switch
>> in the NEMA box at the base of my tower.  Had I installed the Polyphasers
>> at
>> the shack end, only one coax run (between the shack and switch) would have
>> been protected; the switch and antennaa coax runs into it would have been
>> vulnerable to lightning damage.  I installed the Polyphasers in the box on
>> the tower so as to provide protection for the switch and all three coax
>> lines going into the switch.
>>
>>      As for the need for a final Poly outside my shack, I concluded that I
>> didn't need one there for a few reasons.  The run is short (<50 feet); it
>> is
>> underground; based on these these two facts it would be nearly impossible
>> for a lightning strike to induce appreciable energy on the center
>> conductor
>> of that 50 feet of coax such that I would need another Poly outside my
>> shack.  (We all agree that lightning supressors are intended to shunt the
>> center conductor to ground during a lightning strike, right?)  Any induced
>> charge on the shield of my underground coax would be grounded at the NEMA
>> box and at my SPG outside the shack.
>>
>>      As I previously wrote, if I had run the coax directly into the shack
>> to
>> connect to the switch there, I would have installed Polyphasers outside
>> the
>> shack on the SPG and not inside the NEMA box.  If Larry KN8N has a switch
>> on
>> the tower, he ought to put the Poly's there.  Otherwise, I agree - outside
>> the shack on the SPG.
>>
>> 73 de
>> Gene Smar  AD3F
>>
>>
>> ----- Original Message -----
>> From: "Jim Brown"<jim at audiosystemsgroup.com>
>> To:<towertalk at contesting.com>
>> Sent: Saturday, September 11, 2010 11:53 AM
>> Subject: Re: [TowerTalk] Lightning Protection Question
>>
>>
>>> On Sat, 11 Sep 2010 10:57:06 -0400, Gene Smar wrote:
>>>
>>>> It depends.  I have my Polyphasers at the NEMA box at the tower base,
>>>> but I also have a remote coax switch there, too.
>>> I disagree (and agree with K1TTT) -- lightning protection devices are
>>> protecting you radios by short the voltage on the center conductor to
>>> the shield. They cannot do that at the tower -- voltage can be induced
>>> on the coax between the tower and the shack, and a protector at the
>>> tower is too far away to offer much protection at RF. The best place for
>>> them is at the entry  panel to the shack.
>>>
>>> The SHIELDS of coax SHOULD be bonded at top and bottom of the tower.
>>>
>>> 73, Jim K9YC
>>>
>>>
>>>
>>> _______________________________________________
>>>
>>>
>>>
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>>
>>
>>
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