In plain language: SWR changes when feed-line movement changes coupling, common-mode current, connector contact, or the antenna geometry seen at the measurement plane.
Why an operator notices it
If touching or moving coax changes the reading, the line is giving you evidence. It may be acting as an unintended conductor, pulling on a weak connector, or moving relative to the radiator and return system.
Decisions that matter
- Stop changing antenna length until the feed line is mechanically stable.
- Check the intended counterpoise or radial connection.
- Compare readings at the same reference plane and cable layout.
A useful field check
- Test at low power.
- Move one section of cable while watching for repeatable change.
- Substitute a known-good line and restore the documented routing.
Common wrong turns
- Tuning around a loose connector.
- Adding random ferrite before restoring the RF return.
- Calling every movement-induced change a bad antenna.
Technical foundation
This lesson translates established transmission-line and antenna practice into a field decision. Use the current equipment datasheet and Chameleon product guide for changing loss, power, connector, installation, and compatibility limits.
