ATU4K

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 www.trueladderline.com and Blue Ridge Amateur Radio. The original design was conceived by Gary Baker (K7EMF) and is now being manufactured by Blue Ridge Amateur Radio. The Stepper Tune controller is provided by Gary Baker (K7EMF) of TrueLadderline.com. The Stepper Tune controller may be purchased directly from the TrueLadderLine.com web site. The ATU4K can be ordered directly from Blue Ridge Amateur Radio.

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 plastic case measures 20 x 16 inches.

The ATU4K capacitor system is comprised of a Jennings 5-1000pf vacuum variable capacitor controlled by a dedicated stepper motor. The ATU4K also comes with 1000pf of fixed capacitance, which is switched into the circuit using a military grade vacuum relay. The entire capacitance of the ATU4K can be switched from the load side of the circuit to the source side of the circuit, giving the user complete control over situations where the feed line impedance may vary from very low resistance values to very high impedance values.

ATU4K 1:1 current balun

The ATU4K comes with a 1:1 current balun based on an FT24-43 ferrite core with 14 turns of RG-400 multi-conductor core coax. The balun resides on the input side of tuner in order to better block CMC from coming back into your shack.

Vacuum Varible Stepper Drive

The Jennings vacuum variable capacitor is actuated via a dedicated stepper drive motor. The vacuum cap can be individually adjusted via the StepperTune Control Head.

Roller Inductor Belt Drive

The roller inductors are chained together via a belt drive system attached to a dedicated stepper drive motor. The belts are off the shelf products from McMaster Carr.

Chassis mounts

The aluminum chassis of the ATU4K is mounted to the component mounting plate within the weather proof case using 3 1/4 inch bolts. The entire tuner can be easily removed from the weatherproof enclosure by simply removing the mounting screws holding the component mounting plate in place. There is one screw at each corner and there is plenty of room within the housing to access everything.

ATU4K

Here's a picture of the ATU4K mounted in the weather proof case. The through holes and glands for the control wiring (CAT 5 cable) and coaxial connector have not been added to this particular case yet.

ATU4K Weather Proof Case

This high impact plastic weather proof case can be mounted on a tower, post or even to the side of your house, which will allow the user to run coax into the house and ladder line (or window line) up to the antenna.

ATU4K

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