[TenTec] RF Ground

[Bob McGraw - K4TAX]

A real world testimonial like this is worth 10,000 words.

Thanks Billy.

73
Bob, K4TAX


----- Original Message ----- 
From: "Billy Cox" <aa4nu at ix.netcom.com>
To: <Gary at doctorgary.net>; "Discussion of Ten-Tec Equipment" 
<tentec at 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 at 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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