I read somewhere, maybe from Polyphaser's notes, that the purpose of the
tower ground system is to spread the charge caused by lightning to as much
earth as possible. There is obviously a point of diminishing returns as the
charge is spread beyond a certain distance.
73, Keith NM5G
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Dick Green WC1M
Sent: Sunday, August 12, 2007 10:57 PM
To: 'Hardy Landskov'; 'Jim Brown'; 'Tower Talk List'
Subject: Re: [TowerTalk] Ground System
According to literature from Polyphaser, if the ground systems are separated
by more than 75 feet, they don't "see each other", so it doesn't make sense
to bond them. I believe the reason is that the inductance of the connecting
wire or strap is too great at that length to allow the systems to float to
the same potential.
I hadn't read that tidbit when I installed my first tower system, so I laid
265 feet of 1/0 wire at the bottom of the trench to connect the tower ground
to the single point ground at the house. I'm pretty sure that was
unnecessary (I like to think of it as a really long horizontal ground rod.)
When I installed my new tower this year, which is about 225 feet from the
shack, I omitted the bonding wire. I was convinced not only by Polyphaser's
argument, but also by the fact that the outer conductors of the two 1-5/8"
runs of heliax between the tower and shack would undoubtedly present a much
lower impedance path back to the shack than any wire or strap I could lay in
the trench. I'm hoping the tower ground system is robust enough to dissipate
any surges that may occur.
73, Dick WC1M
> -----Original Message-----
> From: Hardy Landskov [mailto:n7rt@cox.net]
> Sent: Sunday, August 12, 2007 8:02 AM
> To: Jim Brown; Tower Talk List
> Subject: Re: [TowerTalk] Ground System
>
> At 07:15 AM 8/12/2007 -0700, Jim Brown wrote:
> >On Sat, 11 Aug 2007 23:34:08 -0400, Ron Todd wrote:
> >
> >>I have installed a ground system for my new tower.
> >>Should I connect tower ground system to the house ground ?
> >
> >ABSOLUTELY! All grounds must be bonded together for a safe
> >installation. That means a ROBUST and LOW IMPEDANCE (SHORT) path.
> >
> Jim,
> With 2½ acres, tying everything together becomes an expensive and
> daunting task. One tower is 150 ft from the house. Any suggestions?
> Hardy N7RT
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