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Old August 24th 08, 08:36 AM posted to rec.radio.amateur.antenna
Ian White GM3SEK Ian White GM3SEK is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 232
Default How do you get a ground rod to 6 feet ?

Fred McKenzie wrote:
In article , Dave Lemper
wrote:

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.


Dave-

Last year there was a discussion here about sinking a ground rod using
an "SDS Plus" Hammer Drill set to hammer-only. I think it was Ian
White, GM3SEK, who proposed that method.


The other point was that SDS+ bits are available up to 1.0 metres long,
so by using both rotary and hammer action you can drill a pilot hole
through most kinds of rock down to that depth.

There is also an article at
http://www.n4lcd.com/groundrod/ that proposes a slightly different
method of coupling the hammer drill to the ground rod.

The question is whether Caliche can be penetrated by such a method. Has
anyone tried it?

We don't have caliche here, by that name, but from accounts on the web
I'd doubt if it could be penetrated by hammer action alone. However, it
seems more likely that an SDS+ bit could drill through it.

Another consideration is whether or not there is moisture in the soil
below the Caliche. If not, then it might not provide a low-impedance
ground even if you could penetrate it!


That is certainly the problem at this QTH, where an earth rod drilled
and hammered into the very rocky subsoil produced a resistance of
500ohms! Long horizontal electrodes are the only kind that work at this
QTH.



--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek