Why an antenna mismatch isn't just a signal-strength problem — it can send real power straight back into your transmitter.
Feed a transmission line into a load that perfectly matches its characteristic impedance and every watt you send travels forward and gets absorbed — nothing comes back. Feed that same line into an antenna, connector, or cable that isn't well matched, and some of that forward power reflects off the mismatch and travels back toward the source. Where the outgoing and returning waves overlap, they interfere — and the result is a standing wave: a fixed pattern of high-amplitude and low-amplitude points along the line that doesn't move. VSWR is simply how we measure how severe that pattern is, and by extension, how much power is coming back at the transmitter.