[TowerTalk] [Bulk] Re: [Bulk] Re: copper or galvanized ground rods in red SC clay

Roger (K8RI) on TT K8RI-on-TowerTalk at tm.net
Mon Jan 11 05:57:49 EST 2016


My thoughts on a ground system.

When you go through the calculations, my current preference is based 
partly on these regs, calculations and experience.

"I believe" a tower of any type should be planted enough concrete(don't 
go overboard) to serve at least, a small UFER ground with some sort of 
network resembling a star.  All this in conjunction with a single point 
ground (SPG) .  Often, construction does not allow a true SPG in many 
homes. Wiring lengths and route in the house can make a true SPG, 
impossible. Rare is the house where the station leads, cable, phone, 
electrical, TV/satellite can form a true SPG. And where it does, are all 
leads from the SPG to the equipment, the same length?

It's not just the SPG, but a well designed electrical system that allows 
for the station to use a SPG for the most benefit.
I have, Phone, Cable (Internet), fax, CAT5 network, and servers. Cable, 
electrical, and hard wired telephone come in through the front, while 
every thing else comes in through the back. The only problem has been 
that CAT5 network, but that has been solved. with high speed wireless 
and parabolic reflectors to keep the receive angle narrow while the 
power between the den and shop is high allowing for near gigabit 
wireless.  Only one computer remains in the shop with no network storage 
out there.

For most hams, the cost of a real, efficient ground system is not 
realistic, from a cost, and / or area standpoint, so we do the best we can.
Follow good practices and put as much as you can afford into a good 
safety ground.

Were I to do it over, when I was working and not living on a pension and 
SS, I'd put up a heavy duty, 120' crank up in place of the 100' 45G plus 
a 70 or 80 footer by the back of the shop.

I have a rather elaborate safety, ground system in a more or less star 
with over 600 feet of bare #2 and 32, or 33 fround rods that cover a 
wide area of our one acre lot.  That was when Copper was a fraction of 
today's prices ans steel was abt 1/4 to 1/3rd of today's prices.

Remember:  No practical ground system provides 100% protection
The US Military uses huge UFER grounds for bunkers in desert 
conditions.  I havent heard of any complaints.

73

Roger  (K8RI)


On 1/10/2016 Sunday 3:48 PM, jimlux wrote:
> On 1/10/16 11:40 AM, David Robbins wrote:
>> At lightning current densities and time scales the earth ionizes and 
>> rapidly
>> increases its conductivity.  See equations by Weck and others:
>> http://www.ipstconf.org/papers/Proc_IPST2011/11IPST109.pdf
>>
>> Note in the graphs how the effective resistance of the ground 
>> decreases as
>> the current increases.
>
> Very interesting..
> (and, of course, there's about a 3:1 difference among the various 
> models, which I'd sort of expect)
>
> That paper and the references it cites will give me a fair amount of 
> reading.
>
> However, I don't see any sort of "saturation" behavior: in fact, it's 
> more of a negative resistance (i.e. resistance goes down as current 
> goes up).
>
>
>>
>> David Robbins K1TTT
>> e-mail: mailto:k1ttt at arrl.net
>> web: http://wiki.k1ttt.net
>> AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373
>>
>>
>>
>> -----Original Message-----
>> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
>> jimlux
>> Sent: Sunday, January 10, 2016 17:42
>> To: towertalk at contesting.com
>> Subject: Re: [TowerTalk] [Bulk] Re: [Bulk] Re: copper or galvanized 
>> ground
>> rods in red SC clay
>>
>> On 1/10/16 8:56 AM, Roger D Johnson wrote:
>>>
>>>
>>>
>>> Another factor not usually considered by hams is that conduction
>>> through the ground is NOT the same as conduction through a copper
>>> wire! A copper wire has a copious supply of free electrons and will
>>> happily conduct increasing amounts of current until it melts. In soil,
>>> the conduction is by ions from metallic salts in the earth. The supply
>>> of ions is finite and when all are being used to conduct electric
>>> charges, the resistance rises sharply. The soil has gone into
>>> "saturation".
>>
>> do you have a reference for this?  I'm interested in a more technical
>> description of the phenomenon.
>>
>> I'm familiar with some other soil and tissue conductivity phenomena 
>> relevant
>> to RF having to do with the ion mobility (e.g. the Cole-Cole model 
>> which is
>> used for all sorts of things at all sorts of frequencies:
>> prospecting for ore, measuring the ripeness of produce, and RF 
>> imagery of
>> human bodies)
>>
>>
>>    A lightning ground system
>>> has to be designed to dump the current from a strike into a large
>>> "volume" of earth capable of conducting the strike current.
>>>
>>
>>
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk


-- 

73

Roger (K8RI)


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus




More information about the TowerTalk mailing list