[Lf] Is a well a good Tx ground?]

[Andre' Kesteloot]

Bill Ashlock wrote:

> Hi Stewart,
>
> Looks like you have performed some thorough experiments in determining the
> resistance of your well system. My experience, however, indicates that the
> ground resistance for which your vertical antenna would be working against
> is the surface resistance surrounding the base of the antenna. This would
> extend to a radius of at least the height of the antenna, and possibly twice
> the height of the antenna. There are some Lowfers that swear that using
> ground rods, reduces the ground resistance seen by the antenna, but others,
> like my self, find no improvement with these rods. The benefit of the rods
> may be a function of the general conductivity of the ground, which at the
> east coast of the US where I am located, is very poor.
>
> Bill C is right on the money in his warning about your trees being a
> potential problem. My tests have indicated the need to be at least 50 ft
> from them. The trees will effectively lower the total Q of your antenna
> system and it will appear (based on your antenna current measurements) as
> though the ground resistance is high.
>
> Good luck to you.
>
> Bill, WA
>
> >From: "Stewart Nelson" <sn at scgroup.com>
> >Reply-To: "Stewart Nelson" <sn at scgroup.com>
> >To: <lowfer at qth.net>
> >Subject: [Lowfer] Is a well a good Tx ground?
> >Date: Fri, 28 Jan 2000 13:24:36 -0800
> >
> >Hi all,
> >
> >I am planning a new lowfer Tx, and thought that my well might be
> >an excellent ground.  It's eight inches, and goes down 100 feet.
> >The water level is now only about one foot below ground, and
> >rarely drops below ten feet.  Sometimes there is even a small
> >artesian flow.
> >
> >I made a rough measurement of DC resistance.  There is a pond,
> >the edge of which is about 50 feet from the well.  I connected a
> >12 VDC supply from the well casing to a pie tin submerged in the
> >pond.  About 50 mA flows.  About 100 feet from the well, in the
> >opposite direction from the pond, I drove a shovel into the
> >ground.  With the supply off, the voltage between shovel and
> >well is about 200 mV (battery formed by difference in metals).
> >When the supply is turned on, the voltage increases by 25 mV,
> >so the well resistance appears to be about 0.5 ohms.
> >
> >Do you think that this is a reasonably valid measurement?
> >If not, how can it be improved?  If so, how might it relate
> >to impedance at 180 kHz?  Is it worth repeating the experiment
> >using an audio oscillator and scope?
> >
> >Unfortunately, there are a couple of trees (deciduous, currently
> >bare) about 12 feet from the well.  Will this wipe out any
> >advantage of a low impedance ground?  Does it make sense to
> >locate the antenna some distance away, and connect a ground
> >radial to the well casing?
> >
> >With a low ground impedance, it seems that loading coil Q
> >becomes more important.  I would think that a suitable
> >ferrite core would help, but most lowfers use air core coils.
> >Why?  How low an effective resistance can be achieved?
> >
> >Any advice greatly appreciated,
> >
> >Stewart Nelson  KK7KA
> >
> >
> >
> >
> >
> >
> >
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