A Feedline Energy Analysis - Amateur Radio

An Energy Analysis at an Impedance Discontinuity in an RF Transmission Line, Part I

Where Does the Power Go? [1] There continue to be many differing responses to the question within the amateur radio community and, so far, no one has presented the facts of the physics of power as understood from the field of optics.

Those facts from optics have been known and understood for decades and are consistent with the laws of physics and the equations governing the behavior of RF transmission lines. Light and RF waves are both composed of electromagnetic energy. Most of the following information comes from "Optics" [2]. In the field of optics, irradiance is the same thing as power in an RF transmission line if the cross sectional area of the transmission line is taken into account.

Irradiance has the dimensions of energy per unit area per unit time. If the light beam of a particular laser occupies the same cross sectional area as a particular coaxial RF transmission line then the irradiance of the laser beam is comparable to the RF power in the transmission line. The 1/4 wavelength thin-film deposited on glass to obtain a non-reflective surface performs in a virtually identical way to a 1/4 wavelength series matching section in a transmission line. Single-source RF energy in a transmission line and laser light are both coherent electromagnetic energy waves that obey the laws of superposition, interference, conservation of energy, and conservation of momentum.


Where Does Power Go?