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I want to work out a design for a linear loaded off center fed vertical
dipole for 75M (perhaps will work multiband as well?) using linear loading in an "S" configuration, i.e: feedpoint I-----------------------------------()-------------I I I I----------------------------------I I------------I I I -----------------------------------I I------------- Which per my reading should let me design a 75M vertical that is only 60% of the length of a conventional radiator. A recent article in QST showed the successful use of 450 ohm ladder line with interwoven 3rd wire as a conveient way to build this sort od linearly loaded design. In attempting to model this design in EZNEC, I do not seem to get the loading effect and shorter length of the radiators to achieve resonance, nor do I get the feedpoint impedance lowering that is described for this sort of loading. I was hoping that the OCFD design would allow direct feed through a choke balun without having to deal with impedance transformations. with either an excessively low center feed impedance (with loading) or the typical ~200 feedpoint impedance and 4:1 balun required with the OCFD design at about 1/3 distance from one end. Any thoughts or prior experience to share? Steve KQ4WB |
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