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Re: [TowerTalk] SPG or whatever it is called now, to coax entrance grou

To: kb2m@arrl.net
Subject: Re: [TowerTalk] SPG or whatever it is called now, to coax entrance ground question
From: jimlux <jimlux@earthlink.net>
Date: Fri, 18 Jun 2010 15:22:38 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
kb2m@arrl.net wrote:
> 
> -----Original Message-----
> From: Jeff KB2M [mailto:kb2m@comcast.net] 
> Sent: Friday, June 18, 2010 17:42 PM
> To: 'Towertalk Reflector'
> Subject: SPG or whatever it is called now, to coax entrance ground question
> 
>  I'm getting ready to connect to the SPG located at the power entrance of my
> new house I'm building on my existing property. At this location I have the
> electric, cable, and phone. I tried to locate this at the same side of my
> house where my antennas are but the power company said no, it will go where
> they decide it will go. It has been decided by them to be located about 60
> feet from where my antenna entrance will be. Now as this is what it is, I
> have a few questions. 
>  I plan on digging a 2 foot deep trench, and burying a piece of 4 gauge
> solid copper between the two. I'm going to make long flowing bends as it has
> to run around the front of my house's front porch, around a corner then
> another 20 feet to where my coax entrance will be.
> 
>  How far or close to the house should I place it?

It doesn't really matter.. The goal is to make sure that the two points 
are at "reasonably" the same potential. If it were me, I'd snug it right 
up against the foundation: 1)less likely to stick a shovel through it 
when gardening or driving something into the soil and 2) concrete is 
usually higher conductivity than soil.. might as well take advantage of it.

> 
> At the coax entrance I'm going to place two weatherproof boxes with the
> Polyphasers in them from the two towers. How far away or close to(or on the
> house?) should I place these boxes?

How are you getting the coax into the house? through the back of the 
box? down into the ground and then back up into the house? If the 
polyphaser melts down, you want the burning crud to fall somewhere other 
than on your siding.  Beyond that, think about resistance to mechanical 
damage: bumps, lawnmower/wheelbarrow/ladder strikes.  They should be 
some distance from any wiring inside the wall (phone, network, cabletv, 
power), so that if there *is* a flashover from your antenna system, it's 
not flashing to something that will carry the damage elsewhere. 6"? a 
foot or two?  There's some requirement in the code, but I don't have it 
handy to lookup, and besides, most ham installations aren't "to code" 
anyway (e.g. those Polyphasers aren't "listed antenna discharge units" 
and I'll bet you're not running your coax in metallic raceways/conduit 
the entire distance from the antenna, either)

Think practicality.. accessible for service, not where it will get 
banged into or forgotten, not where it will propagate damage.
> 
>>From this point I will also tie into the two towers with a couple of more
> runs of the 4 gauge copper. One will be about 32 feet the other 75 feet.

Sounds reasonable...
> 
> Any and all advice, or suggestions please as I plan on digging tomorrow
> morning.


Make sure you lay extra runs of conduit, bigger than you think you'll 
need.  In some sense, the extra hours you have to work at your job to 
pay for the conduit are probably less than the hours you'd spend digging 
the trench a second time.  (although, it *is* easier digging it back 
up.. usually fewer rocks to remove, if nothing else)

> 
> 
> 73 Jeff kb2m
>
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