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K7ITM wrote:
In fact, you don't even need to find the minimum and the maximum points. Again, given sinusoidal excitation and a uniform line, some small set of points with accurate amplitude measurement at each will suffice, since they will uniquely determine the amplitudes of the two waves and the line attenuation. You would have to know the spacing of the points and that they were dense enough that there is not a spacial aliasing problem (points distributed over more than 1/4 wavelength...). Which points out, once again, that the phase information in a standing wave is contained in the amplitude, not in the phase. W7EL measured the *phase* of the standing-wave current which is known not to contain any information as it is close to unchanging all along a 1/2WL dipole or 1/4WL monopole. Yet he reported it as meaningful. So far, nobody has made meaningful phase shift measurements through a loading coil. It's common to think of a standing wave as the result of two travelling waves, one in each direction, but another way to think of a standing wave pattern is as a pure standing wave plus a pure travelling wave. One cannot get away from the fact that the pure standing wave is the superposition of equal amplitude traveling waves flowing in opposite directions. Some part of the forward traveling wave must be allocated to the standing wave function. That part of the traveling wave transfers no energy. |Ifor| - |Iref| = |Ifor'| the part of the forward traveling wave that is transferring energy. |Ifor| - |Ifor'| = |Ifor''| = |Iref| the part of the forward traveling wave that is contributing to the pure standing wave and transferring no energy. -- 73, Cecil http://www.qsl.net/w5dxp |
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