Topband
[Top] [All Lists]

## Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculati

 To: "Doug Turnbull" Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations. Eddy Swynar Thu, 18 Dec 2014 18:28:28 -0500 mailto:topband@contesting.com>
 ```Hi Doug, As I understand it, the velocity factor of 50% applies for radial wires that are simply laid atop the ground, & not buried in any way... But of course, I COULD stand to be corrected..! ~73~ de Eddy VE3CUI - VE3XZ On 2014-12-18, at 4:18 PM, Doug Turnbull wrote: > 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 > > > > > > > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband ```
 Current Thread Topband: Confusion in ON4UN's Low Band DXing radial length calculations., Doug Turnbull Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations., Eddy Swynar <= Re: Topband: Confusion in ON4UN's Low Band DXing radial lengthcalculations., k8bhz Re: Topband: Confusion in ON4UN's Low Band DXing radial length calculations., Jim Brown