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
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|