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## Topband: Confusion in ON4UN's Low Band DXing radial length calculations.

 To: Topband: Confusion in ON4UN's Low Band DXing radial length calculations. "Doug Turnbull" Thu, 18 Dec 2014 21:18:11 -0000 mailto:topband@contesting.com>
 ```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 ```
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