Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations.

[k1fz at myfairpoint.net]

     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 at 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 at 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 at hughes.net [mailto:k8bhz at hughes.net]
  > > Sent: 19 December 2014 00:08
  > > To: Doug Turnbull; Topband at 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 at 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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