Barry,
Are they copper(-clad) or galvanized? The pH of the soil is a factor
in choosing the correct material for your grounding system. An acidic
pH (6 or lower) would indicate you'd be better served by aluminum/tinned/
galvanized whereas an alkaloid pH (7 or higher) would make copper your
material of choice. As a general rule, the eastern states tend to have acidic
soil whereas the western states tend toward alkaline.
The sphere of influence of a ground rod is considered to be twice its length
<bold> in conductive soil <unbold> rather than simply twice its length.
Therefore, 8' rods in 4' of conductive soil should be spaced 8' apart. The
problem, of course, is that it is difficult to ascertain how much of that soil
is conductive (and especially when a ground system exists already). That's
why I personally use a multiplication factor of 1.5. So our 8' rods would be
spaced 12' apart.
Even if the rods presently emplaced are corroded they will have some effect.
I would probably use the same factor as above when emplacing additional rods.
Remember, the rods should be a few inches below grade and interconnected
with low-impedance wire (#2 is the absolute minimum, but 2/0 or 4/0 is better;
and 1.5"-wide copper strap's better still).
73,
Bob Wanderer AA0CY
Sr. Applications Engineer
PolyPhaser Corp.
----------
From: Barry Kutner[SMTP:w2up@itw.com]
Sent: Sunday, September 14, 1997 8:51 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Replacing/adding ground rods
I am planning on adding (or replacing) some ground rods to my tower
ground. The present rods have been in about 8 years. Should I
assume these are corroded, leave them as is, and just add additional
rods/connections as if they don't exist? Would there be any harm in
leaving the old rods connected, such as oversaturating an area of
ground in case of a hit?
Tnx/Barry
--
Barry Kutner, W2UP Internet: w2up@itw.com
Newtown, PA FRC alternate: barry@w2up.wells.com
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