Standing wave & VSWR

When a forward wave on a line meets its own reflection coming back, the two overlap and freeze into a standing wave — a pattern of fixed peaks and valleys that doesn't travel anywhere, like the humps on a plucked guitar string. At some points the forward and reflected waves add up to a tall maximum; at others they cancel to a deep minimum. The VSWR (voltage standing wave ratio) is simply the ratio of that tallest peak to that deepest valley, a single dimensionless number that tells you at a glance how badly your line is mismatched.

A VSWR of 1:1 is perfection — no reflection, no standing wave, a perfectly flat line delivering all its power forward. As the mismatch worsens the ratio climbs: 2:1 is a common 'acceptable' limit for an antenna, while 10:1 means most of the power is sloshing back and forth uselessly, heating your transmitter and possibly damaging it. VSWR ties directly to the reflection coefficient — VSWR = (1+|Γ|)/(1−|Γ|) — so every ham radio operator squinting at an SWR meter on the back of a transceiver is really reading out |Γ| in disguise, checking whether the antenna is happily swallowing power or angrily spitting it back.