Thanks Tree
Similar to a BOG antenna that self terminates beyond a length per
band/frequency.
Exceptions: dry sand & other non conductive surfaces
73
Bruce-K1FZ
On Fri, 19 Dec 2014 07:07:35 -0800, Tree <tree@kkn.net> wrote:
Radials on the ground do not have a magic length. Worrying about resonance
> for them is not necessary.
>
> If you tune a quarter wave wire up in the air - then lay it onto the ground
> - it couples to the ground and is no longer a distinct single piece of
> wire. Just make them an easy length to deal with and put as many of them
> down as you can.
>
> Tree N6TR
>
> On Fri, Dec 19, 2014 at 2:28 AM, Doug Turnbull <turnbull@net1.ie> wrote:
>
> > Brian,
> > I understand that the VF varies with soil type. One could just
> > compensate by being conservative but who wants to use 30/40% more
wire than
> > needed. Why does the ON4UN book ignore VF when doing the example
> > problems?
> > Should I shorten to take into account VF?
> >
> > 73 Doug EI2CN
> >
> > -----Original Message-----
> > From: k8bhz@hughes.net [mailto:k8bhz@hughes.net]
> > Sent: 19 December 2014 00:08
> > To: Doug Turnbull; Topband@contesting.com
> > Subject: Re: Topband: Confusion in ON4UN's Low Band DXing radial
> > lengthcalculations.
> >
> > Hello Doug,
> >
> > The 50-60% figure depends on your soil conditions, so may vary
quite a bit.
> > With my poor, sandy soil, the Vf is 67.7% with the radials laying on the
> > ground. When I buried them 6", the Vf was 39.8%. Using these shortened
> > radials, there wasn't much improvement going beyond 16 radials.
> >
> > To find out your soil conditions, simply lay a temporary dipole on the
> > ground and use an analyzer to find it's resonance. Then trim to
length. Now
> > you have your first two radials!
> >
> > Good luck
> >
> > Brian K8BHZ
> >
> > -----Original Message-----
> > From: Doug Turnbull
> > Sent: Thursday, December 18, 2014 4:18 PM
> > To: topband@contesting.com
> > Subject: Topband: Confusion in ON4UN's Low Band DXing radial
> > lengthcalculations.
> >
> > Dear OMs and Yls,
> >
> > I am replacing raised radials for 160M inverted L with ground mounted
> > radials mostly because I could not readily get the raised radials up high
> > enough in my wood and also because of maintenance problems.
> >
> >
> >
> > This inverted L goes up 100 feet at its top before levelling out for
> > the final 32' or so. It should I believe have a strong vertical element.
> >
> >
> >
> > ON4UN's book Low-Band DXing 56th edition is generally excellent but
> > I
> > do find the coverage of ground radials both confusing and somewhat
> > contradictory. This surprises me for what is pretty much considered the
> > bible.
> >
> >
> >
> > On page 9-14 the text states that the velocity factor falls for
> > ground mounted radials to the "the order of 50-60%, which means that a
> > radial that is physically 20 meters long is actually a half-wave long
> > electrically!" This example is for 80M not 160M. However in the
> > examples
> > found on page 9-15 the velocity factor change is ignored. I understand
> > the velocity factor change and have always accepted this. It generally
> > did
> > not pay to try and cut radials precisely to a given wavelength. I accept
> > the radial length vs. radial number charts but is this an
electrical length
> > in free space or a length considerably reduced due to velocity factory
> > change? Example 3 ignores velocity factor correction and from what I can
> > see this correction is ignore in most of the text concerning ground
> > radials.
> > What does one do? Who does one believe.
> >
> >
> >
> > While I am talking about a 160M inverted L; I did reference the
> > SteppIR BigIR vertical manual, page 18. Lengths should be scalable. I
> > find no mention of velocity factor and the shortening effect which is
> > experienced. The recommendations are not very different from those in
> > ON4UNs book. So does this mean one ignores the change in velocity factor?
> >
> >
> >
> > I appreciate some guidance with this matter. I would like a
> > radial field which would take me to within 0.5/1 dB of the maximum
> > achievable for reducing near field losses.
> >
> >
> >
> > 73 Doug EI2CN
> >
> >
> >
> >
> >
> >
> >
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> >
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> >
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