A real world testimonial like this is worth 10,000 words.
Thanks Billy.
73
Bob, K4TAX
----- Original Message -----
From: "Billy Cox" <aa4nu@ix.netcom.com>
To: <Gary@doctorgary.net>; "Discussion of Ten-Tec Equipment"
<tentec@contesting.com>
Sent: Tuesday, April 07, 2009 1:45 PM
Subject: Re: [TenTec] RF Ground
Gary, do some research on the Polyphaser site, or find a copy
of W. R. Block's book on lightning protection that goes into
details on what to do to PROPERLY protect your setting.
For example, they state when the two points are far apart,
more than 75' IIRC, then running the strap actually adds more
inductance than benefit ... so study what the pros say and
then ponder your situation there.
I am still amazed at the "I'm OK, I disconnect my cables" type
of responses ... I USED to do that until a major strike here
and lots of uglyness with insurance companies.
Short summary is to get insurance again I had to move up to
better/commerical types of protection, and no more "ham lore",
with the results of NO damage here since the strike in 1995.
Commerical stations, FM repeaters and similar don't run out
and disconnect cables when storms approach, and with sound
proper lightning protection ... neither should any of us.
73 de Billy, AA4NU
-----Original Message-----
From: Gary Smith <Gary@doctorgary.net>
Some very interesting ideas and I do appreciate the depth of them as
well.
There is no tower but there are now, Inverted Ls for 160 and 80 that
go up 45-55 feet or so (to the top of the trees and a 40 meter wire
vertical And a Butternut HF9V used for the upper bands. All are
attached to the same radial plate. An Ameritron remote coax switch
1/2 the radials are on salt marsh and I'm using the closest tall tree
to the marsh to loop the antenna wires over. There is a K9AY which is
also at the marsh's edge and it is 250' from the house and 75' from
the closest radial.
There are at least three radials that terminate in a salt water pool
and without a doubt they are the best connection to DC ground in the
entire system. There is a ground rod at the base of the Radial plate
and a ground rod for the K9AY.
I have a "ugly Balun" at the coax insertion to the Coax switch and an
ICE coax lightning protector at the ground rod outside the shack
which is by necessity 60' from the service entrance. I could make a
heavier connection between the coax and the radial plate but all the
connections are already made of coax which has not been thinned out
so I don't understand how adding a wide plate/copper pipe to that
will increase current carrying capacity over that that the braid
itself offers.
I would need 400' of copper pipe or the 18" wide of copper plate to
run from the ground rods at the base of the Inv-L to the service
entrance and I'm not going to do that. The cost is not realistic and
the salty environment would corrode the copper in no time.
I will though look into the Polyphasers and can you suggest a model
number of ferrite for the coax? I'd be happy to add that to what I
have.
At the moment I have two coaxes running into the shack, the one to
the transmitting antennae and the other for the K9AY. Hopefully I'll
have an old tribander rehabbed and up on the roof sometime later this
summer.
My habit is to disconnect coax when I leave the house. I was a novice
in 79 and just bought a brand new Kenwood for my first radio. My
college allowed me to string up a center fed zepp between the tops of
two dorms. I left it connected when I went to class, it got hit and
my top of the line radio that was all of two weeks old was fried when
I came back. Lesson learned to disconnect.
Gary
KA1J
Re: the tower 350 ft from the house. I would bond the ground rods at the
tower to the service entrance ground. I would bond the coax to the
ground rods at the base of the tower, put a big ferrite choke on the
coax at the base of the tower (between the shack and the ground point),
and another before it comes into the shack. I would also have a bond
between the shack and the service entrance. . I would also have
Polyphasers on each coax at the shack to protect the front ends of the
radios.
What this does is start with everything at the same DC potential, and
keep it there when voltage gradually builds in a storm. In the case of a
strike, the ground electrodes are all tied together, but with
considerable inductance between the tower and the house. The chokes
minimize the voltage and current that goes to the shack for strikes of
moderate size. In the case of a strike, the inductance will cause some
gradient between the tower and the house, but the current that equalizes
that gradient is far less likely to go through your ham shack
And, your installation meets NEC, which could be an issue if you have
real damage.
73,
Jim Brown
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