Would it help to run 1/4" copper tubing (as used for refrigerator ice
makers) in the trench? Then bond that to several ground rods and also tape
the coax to that tubing.
Carl
KM1H
----- Original Message -----
From: "Gary Schafer" <garyschafer@comcast.net>
To: <wc1m@msn.com>; <towertalk@contesting.com>
Sent: Thursday, August 16, 2007 9:38 PM
Subject: Re: [TowerTalk] Ground System
>
>
>> -----Original Message-----
>> From: towertalk-bounces@contesting.com [mailto:towertalk-
>> bounces@contesting.com] On Behalf Of Dick Green WC1M
>> Sent: Monday, August 13, 2007 10:32 PM
>> To: 'K4SAV'; towertalk@contesting.com
>> Subject: Re: [TowerTalk] Ground System
>>
>> > Coax shields won't take very much current before they melt. A large
>> ground
>> > wire will lower the impedance between the tower and the common point
>> > ground, as well as reduce the voltage drop for these low frequency
>> > components.
>>
>> RG-8 style coax shields won't take much current before they melt, but as
>> I
>> mentioned, I have two runs of 1-5/8" heliax running between the tower and
>> shack, connected to the tower ground system at one end and the SPG at the
>> other end. For those not familiar with this type of cable, the outer
>> conductor of each run is nearly 2" in diameter -- basically a big,
>> flexible
>> copper pipe with a lot of surface area. I don't have a spec on the
>> thickness
>> of the copper, but it's probably on the order of 1/64". The resistance
>> per
>> foot is .14 ohm/1000 feet. I don't know the current handling capacity,
>> but
>> the power rating is 310 KW. Although the heliax is jacketed, and
>> therefore
>> won't conduct a surge to ground like a bare wire in the trench, it seems
>> to
>> me that the two large copper tubes present a much more inviting path to
>> the
>> SPG than the bare wire. True or false?
>>
>> 73, Dick WC1M
>>
>
> There will be a great amount of capacitive coupling to ground provided by
> those long cables even being insulated. A great deal of lightning energy
> is
> connected to earth by capacitance in any ground system. Yes a DC (bare
> wire)
> connection would be better and help more with the low frequency energy
> coupling.
>
> 73
> Gary K4FMX
>
>
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