On Tue, September 14, 2010 11:20 am, towertalk-request@contesting.com wrote:
> Date: Sat, 11 Sep 2010 22:22:35 -0700
> From: "Jim Brown" <jim@audiosystemsgroup.com>
> Subject: Re: [TowerTalk] Lightning Protection Question
>
> ## in this one case... since big and small coax cables have to be
> interfaced at base of tower, plus braids
> need to also be grnded... a lightning arrestor, imo, is a wise choice.
> It's easily accessible, and also provides
> a demarcation point, and / or test access point. IE: insert test gear
> and either look up the tower... or look back
> towards the shack. In some cases, I can see where the 'base of tower
> arrestor' would take the brunt of the damage.
>
> Later... Jim VE7RF
I just installed my first tower and have been taking pains to implement a
ground system. The first vertical went up 2 years ago with no SPG, and
the hex beam went up last year, again with no SPG, but with the 40' HDBX
up now (and nothing higher for a mile except power lines) I'm trying to do
better.
I ran Heliax up the tower (not 7/8 LDF, but lowly FSJ4 - the price was
right and it's better than LMR400).
That meant I needed flexible jumpers for the beams. I used N bulkhead
connectors grounded to the tower at the top.
I also wanted to use N bulkheads at the bottom to ground the shields, and
also because I need to install a diplexer to combine the VHF/UHF beams,
and I have an RCS-4V HF switch in place, too.
I found that while I could buy an N bulkhead for $5-ish each, I could also
buy AlphaDelta TransiTraps, in bulk, for $12-$13 each.
I went with the TransiTraps, so that the antennas are grounded and
(perhaps) arrested prior to the relay box OR the diplexer.
As a side bonus, maybe it will shunt the lightning strike to ground out at
the tower and keep it away from the house.
110'-ish (IIRC) of the FSJ4 then runs to the house, where the SPG is
located just outside the shack. Shack is in the basement, cables come in
via a window pass-through through a below-grade window-well window.
The pass-through is grounded (but not currently to the service entrance
ground).
I've added a box to the side of the window well, grounded to the window
well (and soon to the service entrance) and inside you'll find another
pair of the TransiTraps (and if I should really replace them with
something else, I'm willing to do that at the entrance, but desire a
DC-pass-through device) along with ICE arrestors for the rotor control and
weather station.
(Rotator is ground mounted, and not suppressed at the tower)
Jumpers from the TransiTraps to the pass through, then 15-20' of coax to
loop around to the radios.
The arrestors at the tower were:
1) not much more expensive than the bulkhead connectors
2) may protect the switch box and/or the diplexer
3) may shunt the strike to ground away from the house.
The Heliax run to the shack is in conduit, under ground, to avoid picking
up induced currents (and to avoid tripping!), but the arrestors were added
outside the entrance because I knew they could still pick up some
lightning along the way.
I still need to bond the service entrance with cable entrance grounds -
I'm planning 30' of 1/2" copper pipe for that purpose. The shack is at
one end of the house, the service entrance at the other, but at least on
the same side.
Bonding the two grounds together and getting the ground rods in at the
tower (and radials in place) is next on the list before the ground
freezes.
> Message: 10
> Date: Tue, 14 Sep 2010 13:20:02 -0400
> From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
> Subject: Re: [TowerTalk] another Lightning Protection Question
> To: towertalk@contesting.com
> Message-ID: <4C8FAEC2.20603@tm.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> The only thing I'd add would be a heavy grounding cable from the tower
> to the house and a "radial ground system" out from the tower with ground
> rods about every 16' along all those ground cables including the one
> between the tower and house. 130' is not all that far.
I've read this advice to bury a grounding cable along with the coax
between the tower and SPG.
Why?
What would be more appealing to the lightning? A small, 6 gauge copper
wire, or 1/2" Heliax outer shield (or RG-213)? Especially if you had a
few runs of the coax - what's the advantage of an additional ground wire,
when the coax shield should be shorted to ground at both ends of the coax
run anyways?
Thanks,
-Tom
ke7vux
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|