Date: Sat, 27 Dec 2014 18:48:41 +0000 (UTC)
From: David Gallatin via TowerTalk <towertalk@contesting.com>
To: "TowerTalk@contesting.com" <TowerTalk@contesting.com>
Subject: [TowerTalk] Arrestor placement
Hello all,Somehow I have gotten the idea that one's lightning arrestors are
best placed at the bottom of the tower. This seems logical to me. Then I came
across another piece that said, no, arrestors are to be placed at the shack
entrance panel. Which is it? Or does it matter???73,
David, AA9G
ex W5DCG and KC9EEV
## Install one at the base of the tower AND also where the coax enters the
home. In my case, the two arrestors are 65 feet apart.
The one at the base of the tower is aprx 4 feet above ground. Base of tower
is earth grounded via 3 x 8 foot deep copper clad
ground rods..all cadwelded. 2 ga bare cu wire to each leg of the tower.
Another 65 foot of bare 2 ga cu wire, C clamped to
basement entrance + SPG...where a 4th ground rod is installed...and also
cadwelded. The HOFFI brand lightning arrestor at the
base of the tower serves other functions. It’s the interface between the rigid
coax from the shack to the base of the tower.
Flexible coax from tower lightning arrestor going up the side of the HDX-689
crank up tower. Lightning arrestor in mounted to the
spg is the 2nd hoffi brand arrestor. Remote coax switch box is mounted to the
mast. All braids from each yagi coax is bonded to the
mast via the remote switch box. The lightning arrestor at the base of the
tower bonds the coax braid to the base of the tower... via the
casing of the lightning arrestor.
## Like K1TTT points out, you need a 2nd arrestor where the coax enters the
home. Now if the tower base is close to where the
coax enters the home, then you could get away with only the one arrestor. If
hairpin or beta matches are used on the yagis, the center conductor
will be bonded to the braid of the coax anyway..right at the feedpoint..via the
hairpin or beta match. In the case of the beta match, both the center
conductor and braid are bonded to the boom. Either way, the center conductor
is bonded to the braid..which is then bonded to the top of the tower.
## If it gets past all of that, the arrestor at the base of the tower should
do the trick. If it gets past that, then it has to get past the arrestor at
the SPG.
If you have a OWA yagi, the center conductor is not bonded to anything... and
the arrestor is def required. You could always install a 15-50 uh coil
across the feedpoint of the OWA... which may not be effective for lightning
hitting the center conductor side of the DE. A 3rd arrestor at the top of the
tower would also work with any OWA yagi.
## A 35 uh coil or 12 ga magnet wire wound on a torroid like ICE uses.... at
the spg will also dc ground the center conductor. ICE uses the back emf
across the coil to fire the gas discharge tube that is in parallel with it.
Jim VE7RF
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