I agree with most of what Gene says here, but still maintain that in some
installations, like my own, it's best to use suppressors at both the tower
and shack ends of the main coax run. As in Gene's configuration, my main
tower has an elaborate ground system: 12 ground rods in a radial pattern
connected with low impedance conductors. I have a lot of expensive antenna
switching equipment mounted in the utility cabinet next to the tower. The
suppressors are between several antennas in the vicinity of the tower and
the switches in order to protect the latter. The tower is 265 feet away from
the shack. According to Polyphaser literature, the tower and shack grounding
systems don't "see" each other at lightning frequencies when separated by
more than 75 feet, so I've set them up as essentially independent ground
systems, each with its own set of interconnected ground rods and suppressors
on all coax and control cables.
73, Dick WC1M
> -----Original Message-----
> From: Gene Smar [mailto:ersmar@comcast.net]
> Sent: Saturday, April 02, 2005 3:10 PM
> To: garyschafer@comcast.net; dickgreen@verizon.net
> Cc: towertalk@contesting.com; 'Craig Sande'; 'Craig Lekutis'
> Subject: Re: [TowerTalk] Wet setting conduit?
>
>
> TT:
>
> Polyphaser and ICE and other types of lightning
> suppressors shunt to ground the lightning energy that is
> injected onto the center conductor of the coax. Let's all
> agree on that point. How they do it (provide the shunting
> effect) varies with the design of the device.
>
> Polyphasers have a series DC blocking cap, and a shunt
> gas discharge tube on the antenna side of this cap (
> http://www.arraysolutions.com/Products/ice/33.htm ). ICE
> devices (also at this URL), in addition to the cap and tube,
> have a shunt inductor at the antenna connector (to bleed off
> slowly-building charges) and a shunt resistor on the
> equipment side of the device. Alpha Delta devices (
> http://www.arraysolutions.com/Products/ice/33a.htm ) have a
> shunt tube but no series cap. ALL of these devices are
> designed to shunt lightning enrgy from the center conductor
> to ground, as I said above. *
>
> In my tower system, I installed Polyphaser devices in a
> steel, grounded box at the tower base. I chose this location
> because the ground system at my tower consists of three
> ground leads welded to a dozen ground rods, providing (I
> hope) a fairly low impedance to ground for lightning energy.
> I could have installed the Polyphasers at the shack entrance
> along with my SPG panel as is being suggested by some below.
> However, at this location I have only ONE ground lead to ONE
> ground rod (This rod is actually the last rod, farthest from
> the tower, in my tower ground field system.) In my
> estimation, the tower location provides a much lower
> impedance connection to ground (three leads and many rods) as
> compared with the shack end (only one rod and 50 feet of wire
> to the tower's ground field.) I wanted to dump the lightning
> energy from the Polyphasers into a better ground connection
> - at the tower. Also, this connection was farther away from
> my house than the SPG connection outside the shack. (First
> Rule of Lightning Protection: Keep the strike energy away
> from your shack interior.)
>
> My conclusion is that, given a choice, one should
> connect lightning suppressors 1. to the better (lower
> impedance) ground point and 2. farther away from the shack.
> The recommendation to install such suppressors outside the
> shack, in my opinion, is not a good idea unless the tower is
> also just outside the shack. In this case the lowest
> impedance connection to the ground system is most likely at
> the tower/outside the shack. In my case, the tower is fifty
> feet away.
>
> BTW - Knowing what I now know about the design of
> various suppressors (above), I probably would have selected
> ICE devices. But they don't come in a bulkhead mount design,
> only a flange design. They are not able to be poked through
> the sides of the steel box I have. One can only hope.
>
>
> 73 de
> Gene Smar AD3F
> * I realize that this information is found on the web pages
> of one of the competing vendors - ICE. Caveat Amateur.
>
>
> ----- Original Message -----
> From: "Gary Schafer" <garyschafer@comcast.net>
> To: <dickgreen@verizon.net>
> Cc: <towertalk@contesting.com>; "'Craig Sande'"
> <ae7i@yahoo.com>; "'Craig Lekutis'"
> <craiglekutis@wirelessestimator.com>; "'Gene Smar'"
> <ersmar@comcast.net>
> Sent: Saturday, April 02, 2005 2:09 PM
> Subject: Re: [TowerTalk] Wet setting conduit?
>
>
> > While it doesn't hurt to put protection devices at the
> tower it really
> > doesn't do too much good. Keep in mind that lightning energy on the
> > center conductor of coax has already made it all the way down the
> > tower in the coax. If it hasn't arced over by that time it will
> > probably not by the time it gets to the shack.
> >
> > The whole purpose of the protection device is to equalize
> voltages on
> > all conductors at one place. You always want protectors at
> the shack
> > where everything is tied together (single point ground).
> >
> > Yes grounding the shields to the base of the tower is recommended.
> >
> > Just so some don't get confused about "grounding to a
> single point at
> > the shack". That doesn't mean that you have an elaborate
> ground system
> > at the tower base and then only one ground rod or connection at the
> > shack end. The shack end where the single point ground
> system is also
> > needs an elaborate ground system of its own if it is located any
> > distance from the tower ground system. It should also be
> connected to
> > the tower ground system.
> >
> > 73
> > Gary K4FMX
> >
> > Dick Green wrote:
> > > Not necessarily. According to the ARRL Handbook (or maybe it's the
> Antenna
> > > Book) and Polyphaser, the optimum configuration is to install
> > > lightning suppressors at *both* ends -- at the tower and at the
> > > entry to the
> house. I
> > > believe the main idea is to protect the coax run between
> the house
> > > and tower, which is an important consideration if it's expensive
> > > hardline
> and/or
> > > buried in such a way that it would be hard to replace. I
> would think
> it's
> > > also good to have two sets of shunts to ground in case the
> > > suppressors
> at
> > > the tower get overloaded or fail. The shields should be
> grounded at
> > > both ends as well -- at the tower end to a system of
> ground rods and
> > > radials connected to the tower and at the house end to the
> > > single-point ground.
> > >
> > > 73, Dick WC1M
> > >
> > >
> > >>-----Original Message-----
> > >>From: Gary Schafer [mailto:garyschafer@comcast.net]
> > >>Sent: Thursday, March 31, 2005 10:14 PM
> > >>To: Craig Sande
> > >>Cc: towertalk@contesting.com; Craig Lekutis; 'Gene Smar'
> > >>Subject: Re: [TowerTalk] Wet setting conduit?
> > >>
> > >>
> > >>Your lightning protection devices should go at the house
> not at the
> > >>tower. Ground the shields at the base of the tower though.
> > >>
> > >>73
> > >>Gary K4FMX
> > >>
> > >>
> > >>Craig Sande wrote:
> > >>
> > >>>I finally decided not to risk any compromise to the base by
> > >>>introducing a total of 5 conduits. The pour will
> proceed tomorrow
> > >>
> > >>morning per the
> > >>
> > >>>original engineering. When the dust settles, I will
> take my time
> > >>>installing the conduit runs to the edge of the pier. I'll
> > >>
> > >>probably use
> > >>
> > >>>a NEMA box mounted nearby for the lightning arrestor
> > >>
> > >>devices and have
> > >>
> > >>>the conduit enter directly from below. I'll run a 6"
> > >>
> > >>copper strap from
> > >>
> > >>>the NEMA box to the tower. I'll be sure to snap plenty of
> > >>
> > >>pictures and
> > >>
> > >>>share my experience when complete.
> > >>>
> > >>>Regards,
> > >>>
> > >>>Craig, AE7I
> > >>>
> > >>>
> > >>>Craig Lekutis <craiglekutis@wirelessestimator.com> wrote:
> > >>>
> > >>> Craig,
> > >>>
> > >>> If it's a slab foundation and the PVC entries are
> not near the
> > >>> anchor bolts then it might not be a problem since the
> > >>
> > >>foundation is
> > >>
> > >>> probably designed for its compressive load and its
> overturning
> > >>> moment. However, if it's a pier type design, it may
> be a problem
> > >>> since it could affect interaction with the shaft and
> > >>
> > >>anchor bolts.
> > >>
> > >>> Best practice is to do what you are going to do,
> check with your
> > >>> engineer. You'll find addition information about
> > >>
> > >>foundation design
> > >>
> > >>> at http://www.wirelessestimator.com
> > >>> <http://www.wirelessestimator.com/> .
> > >>>
> > >>> Best regards,
> > >>>
> > >>> Craig
> > >>>
> > >>>
> > >>>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >
> > >
> > >
> >
> >
> >
> > _______________________________________________
> >
> > See: http://www.mscomputer.com for "Self Supporting Towers",
> > "Wireless
> Weather Stations", and lot's more. Call Toll Free,
> 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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