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A comment on W5DXP’s paper “An Energy Analysis at an Impedance Discontinuity in an RF Transmission Line”

Cecil Moore (W5DXP) published a paper entitled “An Energy Analysis at an Impedance Discontinuity in an RF Transmission Line” in World Radio 2005-2006. A copy of the paper is published on his web site.

Under the heading “The General Case Qualitative Analysis”, he states “The following discussion of a generalized impedance discontinuity in an RF transmission line, operating under steady-state conditions, is not intended to replace a conventional quantitative voltage analysis. It is intended instead as a conceptual qualitative energy analysis that extends the voltage analysis and answers that original question: Where Does the Power Go?”.

With the introduction “The following diagram is of a generalized impedance discontinuity in a typical RF transmission line”, he then proceeds to set out some equations that relate quantities he refers to as Pfor and Pref, and their relationships with Zo and the average power in the line.

The problem is that although stating that this is a study of a generalised impedance discontinuity in a typical line the equations offered and relationships ignore the effects of line loss and so do not hold for the general case or for typical lines which have loss and where Zo is not purely real.

At the very outset, the quantitative analysis fails to meet the declared scope and so its conclusions are suspect.


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