Ham Radio: SWR

[last updated: 2020-05-04]
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• When the transmission line and the antenna have different impedances, some of the transmitted power will be reflected back to the transmitter instead of going out to radiate from the antenna. The transmitted wave and the reflected wave interact in the feedline to create a standing wave, per this excellent description from the excellent site:
  (link to:) hamradioschool.com
"The transmitter’s forward power and the reflected power travel in the feedline in opposite directions. The oppositely traveling signals are the same frequency, and they interact in the feedline. The two traveling signals will superimpose, alternating between a constructive superposition in which the signal amplitudes build upon one another to produce a greater combined amplitude, and a destructive superposition that diminishes the combined signal amplitude. For signals of the same frequency the effect is a standing wave in the feedline that oscillates between the constructive and destructive amplitudes."

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eof