Topband: Ground rods (buried copper strap) for folded inverted-L

[ZR]

Dont make the mistake of expecting 40M results to work on 160 and even on 40 
in different ground enviroments. Its a good article but with caveats.
1/4 wave radials are still best, 16-32 of them, 10-20' high, stop when the 
antenna analyzer shows no more change.

Use a screen of galvanized fencing at the base and on the ground extending 
for 50'. Do not connect to anything.

Fencing that is galvanized and then plastic dip coated will last for 
decades; at least in this NH enviroment with regular salt fog and ocean 
storms.

Carl
KM1H

----- Original Message ----- 
From: "wyc" <wycpublic at gmail.com>
To: <Topband at contesting.com>
Sent: Wednesday, October 12, 2011 9:32 AM
Subject: Topband: Ground rods (buried copper strap) for folded inverted-L


I’m planning to put up an inverted-L, using twinlead (akin to half a folded
dipole – some folks call it a folded unipole).  Modeling suggests that the
feedpoint impedance will be about 100 ohms, so I plan to match with a
quarter-wave section of 75 ohm coax.



I’ve read Rudy Severns’ Jan/Feb 2009 QEX article (
http://rudys.typepad.com/files/qex-ground-systems-part-2.pdf ) which
indicates that, with a small number of above-ground radials (e.g., less than
16), radials shorter than a quarter-wave are preferred.  (I plan to use 8
one-eighth wavelength radials.)  Rudy also notes the advantage, in some
instances, of ground rods.



A six foot ground rod doesn’t have much surface area (about 150 sq inches).
I have some leftover copper strap, and am considering burying it (e.g., 6
inches underground) to augment the grounding.



My question is – where is it best used?  A three foot length of four inch
strap has a surface area of nearly 300 sq inches.  If I have 12 feet of
strap, would it be better to bury all of it at the feedpoint?  Or would it
be better to cut it, e.g., into 3 foot lengths, and bury one piece at
feedpoint, and the other three at radially-spaced locations, e.g., ten feet
out (and wired to ground system)?  (Since return current density decreases
with square of distance, there doesn’t seem much point in burying them way
out towards the periphery.)



Can anyone point to published data about placement of multiple ground
rods/connections?



Tnx,



Bill, K2PO
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK


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