Fig, 4. SWR voltage patterns, similar to that shown in Fig. 3, for a number of different types of line terminations. Note range and phasing from open circuit (top) through matched condition (third from top) to short circuit (next to bottomh Effect of reactive loads is similar to open or short, with reflection coefficient of 1,0 for pure reactive loads, capacitance makes fine appear longer and inductance shorter than physical length- Mixture of reactance and resistance changes phase (like reactance) and SWR (like lines 2 and 4} both.
which in turn is determined by the impedance ratio present at the reflection point.
We found that a reflection coefficient of 1.0 exists with either a short circuit or an open circuit as the load on the line, and that in either case the load condition repeated itself every half-wave back from the load, while the opposite condition occurred at the intermediate quarter-wave intervals.
But our examination of what happens when incident and reflected waves get together examined only a few extreme cases, and completely neglected the effects of line losses (attenuation). Let's see what happens when we plug the losses in too, and check out some in-between cases.
Remember that we found a complete cancellation between incident and reflected waves at the intermediate points, in our examples. This could not happen with any losses at all in the line, because the energy making up the reflected wave must always go farther along the line-out to the reflection point and back-than does the incident wave, i he result is an almost, but not quite, complete cancellation instead-which leaves us a very small voltage or current in the incident direction, instead of zero. This is the only effect of small to moderate values of attenuation.
If we terminate a line in an impedance
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