The ATU4K is a remotely mounted, stepper motor controlled, broadcast quality, symmetric L-Network antenna tuner that is built for the most challenging antenna systems. This unit is designed to be mounted outside of the shack in a location that works best for the antenna system. This arrangement allows the user to run 50 ohm coax into the shack, while also taking advantage of the essentially lossless characteristics of open wire line systems.

The ATU4K is controlled through a remote console located in the shack called the Stepper Tune. This control unit drives a set of stepper motors in the ATU4K to affect tuning of the antenna system. The Stepper Tune is completely configurable and can memorize hundreds of different band settings. This allows for quick and accurate band switching from the comfort of your shack.

The ATU4K was developed as a joint effort between and Blue Ridge Amateur Radio. The Stepper Tune controller is provided by Gary Baker (K7EMF) of The ATU4K and Stepper Tune controller may be purchased directly on the web site.

Behold the ATU4K!

Welcome to the best remotely mounted antenna tuner, bar none. The ATU4K is a broadcast quality antenna tuning unit that is fully QRO capable. This unit is BIG. The all weather aluminum case is over 2 feet long and 18 inches wide.

The ATU4K capacitor system is comprised of a Blue Ridge Amateur Radio split rotor cap, with a capacitance rating of 23 - 1100pf value. This is possible through the use of a split rotor design and a Stepper Tune controlled switching system that allows for the largest part of the cap to be removed from the active circuit. Additionally, the Stepper Tune can be used to automatically activate an additional 2000pf of capacitance for use in highly inductive situations.

ATU4K Stepper Drive

ATU4K Rollers and Cap

Vacuum Relays

The ATU4K utilizes a set of military grade vacuum relays for capacitance switching. The balun visible in the picture is from Balun Designs (Roy Lewellan) and is located on the INPUT side of the symmetric L-network.

ATU4K Case

Weather proof, 100% aluminum case.