There are any number of reasons why an antenna system might trick you into
thinking it's defying 100 years of antenna engineering.
Common-mode currents, unintended interactions, etc. Plus, you didn't mention
what vertical it was: if it's a vertical dipole or a end-fed half-wave design
(F12, Cushcraft R-series of verticals, etc.), it's very likely you'd see little
benefit from the addition of two — I assume you meant — radials.
If it's a traditional 1/4-wave monopole (5BTV, DX-88, HF-9V, etc.), then likely
what's happening is stuff in your home and yard is behaving like radials behind
your back.
Which is not to say you can't or shouldn't accept a very well-working system
when you happen upon one. Lots of people have great success with half-slopers,
even though it's not the greatest of antenna designs.
Finally, it's very likely that even with no interactions or common-mode
currents, two radials will have very little impact.
73, kellyve4xt
> From: bcarling@cfl.rr.com
> Date: Mon, 19 Jan 2015 16:54:04 -0500
> To: jimlux@earthlink.net
> CC: towertalk@contesting.com
> Subject: Re: [TowerTalk] w7ekb & ground rods
>
> 910 micro Henry sounds like a very useful loading coil to me!! I have had no
> difficulty using a ground rod as a counterpoise to my vertical. In fact it's
> done extremely well. I added two radios because the experts said it would
> make it work better. It didn't.
>
> Best regards - Brian Carling
> AF4K Crystals Co.
> 117 Sterling Pine St.
> Sanford, FL 32773
>
> Tel: +USA 321-262-5471
>
>
>
>
> > On Jan 19, 2015, at 12:15 PM, Jim Lux <jimlux@earthlink.net> wrote:
> >
> >> On 1/19/15 8:45 AM, Ken wrote:
> >> It seems to me that the ground above my rock layer (@ 36-40”) gets really
> >> dry during the summer. Does that dry dirt have enough conductivity to be
> >> useful? I do not know the answer to that question.
> >>
> >> Are there different answers depending on why we have the ground rod? (RF
> >> ground, power line ground, or lightning protection)
> >
> > Yes..
> >
> > ground rods make terrible RF grounds, in general (where RF is HF and up):
> > skin effect means that wires and rods have high ac resistance. (skin depth
> > in copper at 10 MHz is about 0.8 mils/0.02 mm.)
> >
> > They also have significant series L (1 microhenry/meter for a wire.. so a
> > 30 foot run to the rod is a 10 uH inductor, that's 600 ohms reactive
> > impedance.
> >
> > Rods are really for electrical safety ground and/or lightning ground. And
> > they don't work all that well for that, unless deployed in large numbers.
> > The advantage of a rod is that it's easy to install by driving, but as an
> > electrical connection to the earth, it's just not that wonderful: the
> > surface area is quite small (8 foot rod, 1" in diameter is only 300 square
> > inches. You could probably do better, electrically, by burying a 1 foot
> > square plate (288 square inches).
> >
> >
> > Rods are also used in phone and power line applications.. you drive a rod
> > at every pole (or wrap the ground wire around the foot of the pole when
> > planting it). Even if any one rod has crummy characteristics, there's lots
> > of other rods in the circuit to help establish the common voltage reference
> > and provide a fault current return. I've had telco installers drive a new
> > rod next to the existing rods on the general principle that at least they
> > knew the new rod was in good condition: faster to just do a new rod than to
> > test the existing one.
> >
> >
> >
> > _______________________________________________
> >
> >
> >
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>
>
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