The AlexTune is a small display that can be used to tune a magnetic loop. At resonance (best SWR) the LED is brightest, so you can tune precisely without watching a SWR meter. The Alextune is mounted with a metal bracket on one of the PL connectors on the antenna loop. It measures the field of the antenna which is strongest in resonance. This principle works with every loop antenna, not only with the Alexloop. The clamp fits every common PL plug, so the AlexTune can also be used with other loop antennas that use coaxial cables as radiators. The brightness of the LED varies depending on the band, with the lower bands it shines also in the resonance case somewhat weaker than on the higher bands.