What can cause erratic changes in SWR?

Standing Wave Ratio (SWR) measures the impedance match between your transmitter, feed line, and antenna. A properly functioning antenna system will typically exhibit a constant SWR at any given operating frequency. If the SWR fluctuates erratically, it means the physical or electrical characteristics of the system are changing rapidly. The most common cause is a loose, corroded, or intermittent connection somewhere in the antenna itself or its feed line, which shifts the impedance back and forth as it moves in the wind or changes temperature. Weather events (unless causing physical swaying that reveals a faulty connection), over-modulation, or strong local signals do not directly alter the impedance match of your antenna system, making those distractors incorrect.