I realize while writing this I am probably preaching to the choir\u2026however this is a subject that sometimes is so common we over look it. I heard two guys talking on their CB radios years ago\u2026one said \u201cyour not coming it too good, turn you vis-wars up a little.\u201d<\/p>\n
When setting up an antenna and transmitter system, it is important to avoid impedance mismatching anywhere in the system. Any mismatch means some proportion of the output wave is reflected back toward the transmitter and the system becomes inefficient. When reflection occurs, standing waves are produced in the cable.<\/p>\n
At some points along the line the reflective wave and the forward wave will meet in phase where the resultant voltage is at a maximum (anti-node). At other points the two waves will be out of phase and therefore the resultant voltage will be at a minimum (node).
\nIt is important to note that the resultant wave appears stationary like and does not propagate like a normal wave and does not transfer energy toward the load.<\/p>\n
Not only is this a waste of energy, but because of the voltage nodes and anti-nodes cause damage to the transmission line if the anti-node develops a positive voltage that exceeds the transmission line voltage rating.<\/p>\n
There is a great demonstration video that describes standing waves in an old AT&T training film.<\/p>\n