[TowerTalk] CATV & Phone grounds

[K8RI on Tower talk]

> Here's a thought (probably mentioned previously).  Assuming a tower has a
> good ground system, we still have cables connecting the antennas and other
> equipment on the tower to the house and electronics in the shack.  We want
> to minimize (or eliminate) any lightning following these cables into the
> house.  I know there are fancy commercial systems for this but how about
> bolting a 10' length of galvanized pipe to the tower leg and running the
> cables through it?

Grounding the shiled of the coax is far more effective.

Running through the pipe does form a choke of sorts, but it's still going to 
let a lot through.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com

>
> 73 - JC, K0HPS
>
>
>
> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com]On Behalf Of Jim Brown
> Sent: Tuesday, July 11, 2006 11:55 AM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] CATV & Phone grounds
>
> On Tue, 11 Jul 2006 10:49:32 -0700, Jim Lux wrote:
>
>>How to tie really depends on why you're tying.
>
> Yes. If you think of lightning as DC, you're likely to be in
> serious trouble. IEEE studies show that the energy content in
> lightning has a broad peak around 1 MHz, with significant
> content well above and below that range.
>
> This means that the most important consideration is the
> INDUCTANCE of the network of conductors that tie to each other
> and complete the path to earth.
>
> To answer the original question -- YES, all of these "grounds"
> should be tied together by paths having the lowest possible
> inductance. That means SHORT conductors, and WIDE conductors.
> As others have noted, braid and stranded wiring is bad because
> it corrodes much more quickly than a solid conductor. That's
> why wide copper strap is preferred for RF bonding.
>
> Ideally, from a lightning protection point of view, telco,
> CATV, power, and our ham antennas should all enter the premises
> at the same point so that the bond between them can be very
> short.
>
> In the real world, that doesn't always happen, and the bond
> between them may need to either run through the footprint of
> the house to be short, or must run around the perimeter. That's
> another argument in favor of multiple ground electrodes (rods)
> around the perimeter of the building, all tied together in a
> ring.
>
> It's also important to realize that Standards and Building
> Codes are influenced by political and financial interests (like
> power companies, telephone companies, and CATV companies).
> That's why the requirements for bonding of telco and CATV
> wiring are so lightweight.
>
> 73,
>
> Jim Brown K9YC
> http:audiosystemsgroup.com
>
>
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