ATU4K--Balanced Antenna Tuner, Outdoor (More Details)

(1 review)
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New!!   Symmetrical Antenna Tuning Unit (Air Variable now replaced by Vacuum Variable!).

* Complete ATU Enclosed In Aluminum Weather Tight Enclosure

* Controlled With Two Stepper Motors and Vacuum Relay

* Capable Of Full Legal Limit (RTTY, AM, Etc)

* Wide SWR Bandwidth (On 75M, 1.5:1 Is 95Khz!)

* Wide Impedance Matching Range.  With 459 ohm True Ladder Line Typically 160M Thru 6M

* Minimum FeedLine Radiation In Transansmit and  Reduced Noise Pickup In Receive

* Provides A Truely Symmetrical Feed To Ladder Line

* No Balun Core Saturation and Heating Issues

* Typical Return Loss:  70db!  That Is 1:1 SWR!  

* Enclosure Size:  20 High X 14" Wide X 9" Deep

* Relay Control Voltage: 24 VDC

* RF Wiring Is 1/2" Copper Strap


Note: (1) This ATU Requires A Stepper Motor Controller That Can Control Two Stepper Motors and Two Control Relays (Hi/Low Impedance, Cap 1 In/Out) Such as The StepperTune-BT Listed In Our Store

(2) This ATU Is Strictly A Symmetrical Tuner!  It Will Feed Only Balanced Line To The Antenna!  

(3)  This ATU Is Designed To Be Located Outside Preferably Under The Antenna Feedpoint Near The Ground And Be Fed From The Shack With Low Loss Coaxial Cable Such AS LMR400.  We Suggest It Be Remotely Controlled With A StepperTune-BT Which Gives The Operator Memory Control And Ease Of Operation!

(4) Freight Is Additional.  Upon Shipment, Customer Will Be Contacted For An Additional Payment For Freight Cost (Freight Cost Will Be Discounted-IE, Our Cost And Special Rate If We Use UPS)







       ATU4K Review By Greg Wetzel N

Review of TrueLadderLine ATU4K tuner with StepperTune controller


Reviewer: N8MW. Equipment purchased in March, 2022, Installed in PA station used on 160,80,and 40 meters


Description of installation: ATU installed at 30 ft level on tower which supports the center insulator of a 220 ft dipole with center insulator at 80 ft and ends at 70 ft.height. Antenna fed from ATU with 3 in ladder line, impedance of approx. 525 ohms. The Controller, StepperTune-BT, located inside the shack with a 125 ft run of control cable (Cat 5 ethernet cable). Detailed tuner and controller descriptions are available on


Setup and calibration: After installation completion, the ATU requires calibration with the StepperTune-BT controller. The ATU and StepperTune-BT controller have individual manuals describing the wiring and calibration. Calibration requires some understanding of the construction of the ATU and controller. Upon calibration and synchronization of the units, the system is ready to tune the antenna.


Tuning the ATU: The ATU has balanced inductors and 2capacitors which can be switched in or out of the circuit for either high or low antenna impedance. Selecting the configuration of the ATU components via the StepperTune-BT controller switching for the best match is the first important step in tuning. Once completed, the variable adjustment of the inductors and capacitors can be changed for best match. My tuner was able to match every frequency from 160 meters through 6 meters with a 1.0:1 VSWR. System modeling performed by TrueLadderLine’s Gary (K7EMF) determined at least a 97% radiation efficiency on all bands. StepperTune-BT Controller settings for 16 configurations can be saved and recalled in the memories of the StepperTune-BT controller. The settings of the inductors and capacitors are varied by stepper motors in the ATU. There is a built in jog that allows for fine manual tuning. Tuning is most easily achieved by interactively by observing the SWR on a self calibrating meter, or on a VNA.


Performance: The ATU deserves a 5 star rating for performance because of its outstanding matching capability. No other tuner I have used, including Palstar 5k, BT1500A, 2k, AT-Auto could achieve similar matching. The StepperTune-BT controller is a very precise and convenient way to adjust the ATU. It does require some practice to adjust quickly. Understanding of antennas, transmission line, and tuners technical details is very helpful for using this equipment. I would not recommend this for novices.


Conclusion: This ATU and controller are unique among similar units on the market. No other tuner can achieve the results obtained with this tuner. Because of this, the value of this tuner is difficult to evaluate compared to other units, except to say that it is well worth the cost. Gary, K7EMF is also very helpful in understanding the operation and design. Overall the entire system deserves a 5 star rating.

Greg, N8MW


  • 5

    Posted by John on 14th Oct 2023

    If you are a wire antenna user, I hope you use a TrueLadderLine 600 ohm open wire product ( If not, you are missing out on a great product and the potential for a great antenna system.   With the technical help and guidance of Mr. Gary Baker (K7EMF- owner/operator of and, I erected a single wire 220 ft multiband wire dipole that is only 34' (agl) at the apex. The ends of the dipole terminate at 20 ft above ground. The antenna is fed with  34 feet of TrueLadderLine 600 ohm open wire feedline. It is connected to an external "remote controlled" ATU (balanced T-Network tuner also designed by K7EMF) located at the base of my antenna center support mast. The ATU uses stepper motors that individually tune a variable inductor and capacitor. I then ran approximately 160 ft of RG-213 for the radios and CAT6 (ATU controller) cable into my radio room.  Inside the radio room,  I use another great K7EMF product, a controller ( As aforementioned, the CAT6 cable is used to tune the ATU remotely. With this K7EMF-designed system, I can tune my wire dipole effortlessly from 160m through 15m with NO GAPS. My SWR on any of the bands is absolutely nothing, and the efficiency of the antenna system is beyond belief. No high SWR on the feedline and greater efficiency on the antenna - I am in ANTENNA HEAVEN!  Thank you, Gary K7EMF!   73 de John A Schwamm KA7TXS