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On Apr 2, 8:33*am, Cecil Moore wrote:
wrote: I was wondering if the self shielding properties of the toroid would have contributed to this conclusion, and because of these properties, the toroid not have any electrical degrees, so to speak, so when it come to the radiating element it would need to be slightly longer to see the electrical degrees for the wavelength or resonance frequency injected into it. thanks again for the info. I suspect that the VF of the toroidal loading coil is much higher than the VF of an air-core loading coil, i.e. the toroidal loading coil occupies fewer electrical degrees of the antenna. It makes sense that if the toroidal loading coil occupies fewer electrical degrees of the antenna that those degrees must be furnished somewhere else. The toroidal loading coil seems to be closer to the lumped circuit model than is the large air-core loading coil which generally requires analysis using distributed network techniques. http://www.ttr.com/TELSIKS2001-MASTER-1.pdf There are two things happening with a base loading coil. The loading coil occupies a certain number of degrees, e.g. ~36 degrees for a 75m bugcatcher coil. The stinger occupies maybe ~11 degrees for a total of ~47 degrees. The other ~43 degrees comes from the phase shift at the impedance discontinuity between the coil and the stinger. With a center loading coil, a few degrees are lost at the impedance discontinuity between the base section and the coil. That's why a larger coil is needed for a center-loaded mobile antenna. -- 73, Cecil, IEEE, OOTC, *http://www.w5dxp.com I am a little confused, you say about the coil and the stinger occupying a portion of the total 90 degrees, (I can follow this not a problem), however I thought the purpose of the coil was to add inductive reactance, due to the shortened length of the radiator, less than 1/4 wave, therefore having a capacitive reactance overhaul. Let the shortened vertical be 34-j234 ohms. My understanding is that depending on on what the reactance is at some freq, I need to offset this negative reactance with an equal positive reactance. I wasn't looking at from a degrees point for view. Or is it just 6 of one, half dozen of the other, both be equal just expressed differently, I like the degrees point of view for a couple of other arrays I am experimenting with. (long wires) I think it will simplify things a whole lot. thanks again for the info and the links, very valuable info. 73 brett |
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