Kessler Engineering

The AT-AUTO automatic antenna tuner handles 1.5kW CW operation, employing stepper motors under microprocessor control to precisely position a roller inductor and air-dielectric variable capacitor, avoiding relay-switched discrete components. This design choice prevents loud relay clacking and burning contacts, a common issue with competing products. The tuner features auto-retuning capabilities and receives periodic firmware updates, ensuring continuous improvement and added user-requested features.

Its companion product, the CX-AUTO coaxial switch, also features an embedded microprocessor controller. It enables selection of 1-of-8 coaxial outputs via a serial data interface. When integrated with the AT-AUTO, the tuner can associate specific coaxial outputs with amateur radio bands, automatically commanding the CX-AUTO to select the correct antenna when the operator QSYs to a different band.

Don Kessler began designing the AT-AUTO in 2005, with its debut at the 2006 Dayton Hamvention. Kessler Engineering also offers custom RF product design and electrical engineering consulting, specializing in Class-E RF amplifiers.