G----------------------------C-----------------------------L Generator LowLossCoax Load aka: Source, Zc=50 ohm aka: Transmitter Antenna Z = Impedance c = characteristic E = voltage I = current d = dynamic The Exception: when G, C and L = 50 ohms, these conditions exist. a lossless transmission line having a perfectly matched load termination. a matched condition between the generator or transmitter and the line characteristic impedance, Zc. no reflected power in the line. no reflection loss. The generator delivers what is defined as the maximum-available matched power the load absorbs all the power delivered. The Rule: when G = 50, C = 50 and L = 50 but not = to....... these conditions exist. a mismatch between the line impedance Zc and the terminating load. less power will be absorbed by the load the amount of the reduction in absorbed power resulting from the change in load impedance is the measure of the reflection loss. as the reflected power wave returns toward the generator it causes a change in the line impedance from Zc to Z = E/I all along the line. (Zd / dynamic impedance properties) these properties come into full play whenever G, C and L are not all the same value. when the reflected wave reaches the input terminals of the line the generator is presented with a change in line input impedance from the Zc value to some new value determined by the E/I-vector relationship at the line-input terminals. this new impedance at the line input has exactly the same degree of mismatch to the line Zc as the terminating load that generated the reflection. the line is also now mismatched to the generator in the same degree, and in this condition the generator will automatically make less power available to the line. the reduction of power delivered to the line is exactly the same amount as the power reflected at the load. or........ the reflection loss at the load can be referred back along the line to the generator. thus, reflection loss is simply a non-dissipative type of loss representing only the unavailability of power to the load due to the generator's making less power available to the line as a result of the mismatch of impedances caused originally by the mismatch at the load terminating the line. (That reflection loss represents only the unavailability of power to the load will become evident as it is now shown that the load absorbs all the power the generator makes available to the line.) on reaching the generator terminals and causing the mismatch to the generator, the reflected power is totally re-reflected toward the load, adding to the source power exactly the same amount as the reduction in power made available by the generator. incident power equals source power plus reflected power. the incident power reaching the mismatched load remains the same as before the generator made less power available. the reflection loss therefore now equals the reduction in generator power. now.... if a conjugate match is now provided anywhere along the line, even at the input terminals, the reflected power wave is prevented from traveling past the match point toward the generator. thus, the line impedance between the match point and the generator is now unaffected by the reflected wave and remains at its Zc value. the generator no longer sees a mismatch, and again delivers its maximum-available matched power to the line. the conjugate match has thus provided a negative reflection, commonly called "reflection gain," which exactly equals and cancels the reflection loss. but it has also been shown that all the power delivered by the generator is absorbed in the load.... in either case -- with, or without the reflection gain. the generator simply made less power available before the reflection gain implemented via the conjugate match restored the 1:1 condition between the generator and the line.