As an electro-magnetic wave travels through the different parts of the antenna system (radio, feed line, antenna, free space) it may encounter differences in impedance (E/H, V/I, etc.). At each interface, depending on the impedance match, some fraction of the wave's energy will reflect back to the source, forming a standing wave in the feed line. The ratio of maximum power to minimum power in the wave can be measured and is called the standing wave ratio (SWR). A SWR of 1:1 is ideal. A SWR of 1.5:1 is considered to be marginally acceptable in low power applications where power loss is more critical, although an SWR as high as 6:1 may still be usable with the right equipment. Minimizing impedance differences at each interface (impedance matching) will reduce SWR and maximize power transfer through each part of the antenna system. COUNT 4
QSN1 What is one piece that makes up an antenna system? ANS1 radio QSN2 What is created by a portion of a radio waves energy reversing? ANS2 standing wave QSN3 A term that refers to the highs and lows of power in electro magnetic waves is? ANS3 standing wave ratio QSN4 Impedance matching makes an important difference in what antenna function? ANS4 power transfer