Alpha 4040 Automatic Antenna Tuner

September 2017 Update

The Alpha 4040 Automatic Antenna Tuner has not been released for full Beta testing and production yet as we are solving some firmware issues.  We cannot give you a date nor estimate at this time when full production will commence.

We currently have more pre-orders for the Alpha 4040 than we will be able to fill in the first full year of production.

–Alpha RF Systems

The Alpha 4040, 4 kilowatt, 1.8-30 MHz antenna tuner is nearly complete. We do expect it to ship soon . This brochure will give some of the highlights of the product and some insight into the design choices that went into this exciting new tuner, but the design is subject to change. We are accepting orders on the web site. To make sure you have an opportunity to look at the actual product specifications before purchasing, orders placed will not require a deposit, and you’ll have the right to cancel the order any time before shipment. As with many products in development, delivery estimates may be incorrect.


This document contains advance information on a product under development. All features, functions and specifications contained herein are targets only, and subject to change at any time. The artwork shown is computer rendered and not actual product pictures. As we are able, we will post actual photos of the product.

Development Status

Over a year of development effort has already gone into the Alpha 4040. As the design comes together, we are preparing for product roll-out.

This is planned to occur in several phases. Once we have a prototype working to our satisfaction, we will release a few to some alpha testers. Overlapping this, we will prepare for a larger beta group to smooth out any remaining rough edges.

We are taking pre orders, with no deposit needed, and no withdrawal penalty other than losing your priority order .

So if you are seriously considering purchasing a QRO tuner in the near future, put your name on the list. This will also form the basis for a mailing list, which will allow us to keep you all appraised by email of the development status as it unfolds.

Overall Philosophy

It was decided at the outset that a tuner worthy of the Alpha name had to be something exceptional. In early meetings, there were discussions on price point, size of the unit, power handling margin and many more. We also integrated a lot of user suggestions from various hamventions and trade shows over the years. We decided that the product had to be no compromise and bullet proof . While we would not go over the top with the whole design, we wanted to make sure that this was the best tuner in the market, and in doing so we decided that price would generally take second place to performance in all major design choices. So the design philosophy was to design in quality from the outset, but keep the price within reason.

A color LCD with a touch panel right up front:

Besides the power handling and tuning capability of the Alpha 4040, we decided that we would add a graphical interface to the tuner. This choice allows us to actually show the complex impedance of the load you re trying to tune on an easy to read Smith Chart. The Smith Chart is a standard tool for, among other things, designing matching networks, which of course is the purpose of the Alpha 4040 Auto Tuner. Showing the complex impedance in the form r+jx on a Smith Chart gives you an incredibly simple method to view the actual load presented at the coax. You’ll be able to instantly see if the antenna impedance has changed since installation, and you can easily see if your antenna is capacitive or inductively reactive over a wide frequency range.

Included in our design is a Linux based computer to control everything from command and control of the tuner, to displaying the results of algorithmic computations we can do with Voltage, Current, and Phase of the RF signal that passes through the Alpha 4040. This box will be a great platform for applications and improvements not yet included. Imagine a station monitor, or swept SWR display. With a sampler, an Arm based Linux computer, and a color LCD display, and some software, other applications can tell you quite a bit about the signal you re transmitting.

Choice of Topology

The topology is really the first and most fundamental choice when designing a tuner. Several different arrangements of capacitors and inductors can be used to match high swr loads to 50 ohms. This is really the first and most fundamental choice when designing a tuner. After studying a number of possible options, the classic tee configuration was settled on. One of the reasons for this was the availability of high performance vacuum variable capacitors. We were unable to find a variable inductor that measured up to our requirements, and so we rolled our own . A simplified block diagram of the tuner is shown below. A switched L configuration was the other option that was seriously studied. While this is capable in principle of slightly lower loss, because there are only two matching components for any impedance transformation, this is offset by the need for four relays to switch between the different L topologies needed to cover the whole impedance range. In a 4 kilowatt tuner, these are not small relays, and need to be able to support very high voltages and currents. In the end, it was judged to probably be a less reliable arrangement than the tee.


Circuit Description

Description, the core tee section is comprised of the variable inductor, L1 the vacuum variable capacitors C2 and C3, and the low band pad capacitor C4. The balun is always in the circuit, whether or not the tuner is driving balanced line. This is the way it is done in the classic high power tuner in the ARRL Antenna Book, and is the correct place for it in our opinion. The balun is on the 50 ohm side of the tuner, not on the antenna side. This allows it to be designed for low loss in a matched 50 ohm circuit, and not have to worry about high voltages or currents in mismatched balanced line. In order to operate in unbalanced line coax BAL 2 and BAL 3 are shorted by an internal relay. On the output side there are four coax connectors, and a set of connectors for unbalanced line. These are under control of the embedded control computer, and can be set up to automatically follow as the band is changed on the radio. This gives a great deal of flexibility in station design, but in addition, there will be a number of relay driver outputs that can be connected to a users antenna matrix to further expand the antenna options. This allows, for instance, a user that has their own balanced antenna matrix to connect multiple antennas to the tuner. Assignment of these outputs is under control of the embedded computer. The switch used to select between these is a custom design which is rated for extremely high voltages and currents. Relays K1 and K2 allow the tee network to be bypassed, and the input is then connected directly to the output connectors. All the various output options are still available in this mode. This is the mode the relays will rest in when the unit is un powered. At the common input connector there is an RF voltage transformer and a current transformer. These feed directly to analog to digital A D inputs on the control computer. They are digitized in such a way that the relative phase information is preserved, and this allows forward and reflected power to be computed. In fact, it allows for a vector solution of the impedance real and imaginary parts connected to the tuner with the relays in bypass configuration. This allows the control computer to compute the optimum values for the variable components and preset them, without the need to dip and load.

New Custom made Inductor

Looking for a variable inductor capable of the inductance range and power handling ability needed for this project ended up being a project by itself. There wasn t one on the market that we felt would work reliably. The normal method is to use a small wheel to contact the inductor at the tap point. Using this method is a common failure mode of existing inductors when run at high power.

We designed an edge wound beryllium copper coil and, most importantly, two squeeze contacts that make contact with the coil at four distinct points, each with enough pressure that there is no chance of an arc. Here is a close up of the inductor.


Simple Installation

Besides the power mains connection, there is a minimum of two connections needed to use the Alpha 4040. RF IN and RF OU T. If these are the only two connections used, the Alpha 4040 senses the frequency of the RF. At this time it will start positioning the three elements of the T network to match the LOAD to 50 ohms purely resistive. Spinning the Inductor and two vacuum variable capacitors, even with high power stepper motors takes some time, so we ve included two RCA jacks that can keep the amplifier from keying during this transition period.

If your transceiver has a digital output that includes frequency, you can plug that output into one of the digital inputs. As soon as the frequency of the transceiver changes, the Alpha 4040 tuner will sense the new frequency without the need to sample the RF and start positioning the three elements immediately.

The USB and Ethernet connection can be connected to a computer or a Ethernet switch, and can be monitored and controlled via these ports.

We’ve also included a General Purpose I O connector that can be programmed and used to control external equipment.

Physical Realization


Voltages and Currents

In specifying the ability of a tuner to match antennas with all sorts of different impedances to 50 ohms, there are a variety of ways of going about it. One simple approach is to look at the impedance of the load at the output terminals of the tuner. This can be expressed as a real impedance in series with an imaginary impedance, in the form R jX, where R is the resistive real portion and X is the reactive portion, multiplied by the complex operator j. Without getting too technical, the analysis proceeds by assuming that all the power is delivered into the resistive portion of the load, where it is radiated or converted to heat. The reactive part is cancelled by the tuner in bringing the impedance to 50 ohms, and does not represent a way for the power to be dissipated. It is then easy to calculate the current through R. Since this current flows through both R and X, we can multiply them by the current to get the voltage across each. These are, of course 90 degrees apart, so this must be taken into account when computing the voltage. It is easy to come up with a spreadsheet to do the math, and also show the swr and reflection coefficient at the same time. We can then plug in typical values for some extreme values of impedance. This is shown below

Load Real Load Imaginary Real Coefficient SWR Power RMS Current RMS Voltage Peak Voltage 2 2 .9 25.0 4000 44.7 126.5 178.9 400 4 .8 8.0 4000 3.2 1265.0 1788.7 400 400 .9 16.1 4000 3.2 1788.9 2529.4 2 0 .9 25.0 4000 44.7 89.4 126.5 6 2 .8 8.3 4000 25.8 163.3 230.9 1500 0 .9 30.0 4000 1.6 2449.5 3463.6 2000 2 1.0 40.0 4000 1.4 2828.4 3999.4 50 0 0 1.0 4000 8.9 447.2 632.4

Of course, we specify the input power to the tuner as 4 kW maximum. So this is a little bit conservative, since there will inevitably be some loss of power in the tuner. But it serves to point out the high voltages and currents present just at the load terminals. Voltages and currents in various components inside the tuner can actually be somewhat higher than this. The last line in the table shows the values for 50 ohms. As expected, if the impedance is higher than 50 ohms, the voltage is higher than the 50 ohm value and the current lower. If the impedance is less than 50 ohms, the current goes up and the voltage goes down. Notice the voltage goes up to 4 kV. This is why we used 7.5kV vacuum variable capacitors inside the unit, and the roller inductor has to have special contacts to carry the current. We want to be certain nothing is too close to the edge. In the Specifications section, the impedance range of the 4040 is listed as a function of power into the tuner. On the low impedance side, the limiting factor is the heating produced by current in the inductor. The values listed are conservative, and we are hopeful that we may be able to increase the already wide impedance range even further once we complete testing of the early units.


In a tuner at this power level, there is going to be some waste heat generated. The higher the swr, the more this will be. Many tuners rely on convection cooling, but we wanted to be certain that the AP4040 would not overheat even under continuous duty operation. So there are two temperature controlled muffin fans on the right hand side of the cabinet. These drive the air flow by drawing air out of the unit after it passes over the inductor, which is the component that generates the most waste heat. Room temperature air enters via a grill on the Rear Panel. The requirement to supply room temperature air, and allow the heated air to escape must be taken into account when planning the placement of the tuner.

Control and Interfacing

At the heart of the tuner is a very capable ARM based computer running the Linux operating system. On the inside, the computer has interfaces to the high torque stepper motors, and as mentioned above, it receives tuning information from the swr bridge components. On the user side, there is a large color touch screen display and a tuning knob. This allows the tuner to display everything the user needs to know about its state and operation. The 4040 is capable of fully automatic operation, where the control computer uses the swr bridge information to compute the optimum settings for the three variable components. Once there, it monitors and will continuously null out any residual swr error. It is also possible for the user to override the automatic mode and set the tuner up manually if desired. For more information on the large number of interfaces, see the Front Panel and Rear Panel sections later in this document.

Front Panel


  1. Main Screen This color touch screen can be used in a variety of ways to display and enter data. Text, data and graphics are displayed to help the user integrate the 4040 into their station and adjust it during operation.
  2. Main Control Knob The user can use this to set up the tuner manually or to scroll through lists of options on the main screen.
  3. Forward Power Bar graph This high contrast display is used to display forward power. While less accurate than the power readout on the Main Screen, it can serve as a quick visual check while operating that all is well.
  4. Reflected Power Bar graph In a similar manner to the Forward Power Bar graph , this serves as a quick visual check during operation. Normally this will be very low, but if it rises the user may need to take some action unless the auto tune function is enabled/
  5. SWR Bar graph This shows the swr on the input radio or amplifier side of the tuner. During adjustment the user can either use this display or the Reflected Power Bar graph to optimize the match to the antenna.

Rear Panel


  1. Tuner In In This SO 239 connector is where the amplifier, radio or other source is connected.
  2. Tuner Out 1,2,3, and 4 These four SO 239 connectors connect to unbalanced coax loads.
  3. Tuner Out Balanced These 8 screw posts are used to connect a balanced load open wire, ladder line or twin lead to the tuner. Be aware that high RF voltages can exist on these exposed terminals.
  4. PTT IN, PTT OUT Two RCA jacks for keying loop through. Connect the PTT out line from your transceiver to PTT IN and connect Key OUT to your amplifier. By routing your keying cable from your transceiver to the tuner, and then to the amplifier, the tuner will keep your system from keying the amplifier while the tuner is moving its elements to the proper position. Although no harm will come to the tuner, during the tune time the amplifier will see varying reactance. By looping the amplifier key line through the tuner, you can avoid strange and varying loads on the amplifier or radio.
  5. AC Line in This IEC standard plug accepts the common three pin power cord used on most test equipment and radios. The unit can be powered from 100 240 vac, 50 60 Hz.
  6. Fuse A standard 3AG 1amp 250V fuse for equipment protection.
  7. Serial port This DE 9F connector receives digital band information from any Yaesu, Kenwood, Elecraft or any other radio that generates band information in CAT V standard formats If a custom serial interface is needed, it can be derived easily from the signals on this connector.
  8. CI V Port This 3.5mm phone jack receives digital band information from an Icom or any other radio that generates band information in CI V standard format. If band information is available, the tuner will start selecting the approximate element positions so only a small change and therefore a short amount of time will be necessary to bring the system into tune.
  9. Relays A standard 8 pin Switchcraft Multi Conx connector provides x uncommitted relay drive signals. This allows the user to connect an external antenna selector.
  10. USB IN This is a standard USB Type B connector for connecting the tuner to your computer. Remote control of the tuner, and software updates can be downloaded through either the USB port or the Ethernet port below.
  11. Ethernet RJ-45 A standard RJ 45 Ethernet port connects to a network providing services including http, so you can monitor and control the tuner via any web browser from anywhere in the world. This port can also be used to upgrade the embedded software on the Linux computer.
  12. Air Inlet This is the air inlet for the unit. It must not be blocked during operation of the unit. It is expected that the unit will be operated with normal room temperature air able to enter here. Try to position the 4040 so that hot exhaust air from other equipment is not drawn into the inlet.
  13. General Purpose I/O The 8 connections are available for general purpose switching or sensing of external devices.

Proudly Handcrafted in the USA

This tuner is as rugged and reliable as anything we ve created. We buy the best components available for the Alpha 4040 . Our stringent selection of even the simplest components demonstrates the commitment that we have to deliver the best, most reliable amplifier in the world.

The Alpha 4040 is finely handcrafted and is designed and built in Colorado, USA, comes with an industry leading 4 year warranty. We build them by hand, tune them by hand, and burn them in so we know that when you get your Alpha 4040 , you’ll have a tuner that is the most rugged, best built in the world.


  • Frequency coverage: All amateur frequencies from 1.8 30.0 MHz
  • Continuous Power Input: 4,000 Watts
  • Impedance match range(4kW): 30 – 2000 Ohms
  • Impedance match range(3kW): 20 – 2000 Ohms
  • Impedance match range (2 kW): 10 – 2000 Ohms
  • Impedance match range(1 kW): 4 – 2000 Ohms
  • Impedance match range(600 W): 2 – 2000 Ohms
  • Color LCD Display: Menu and Setup of the various modes, Smith Chart display of actual complex impeden ce, plus other applications not listed at this time. The display is driven by an ARM based microcomputer running Linux.
  • ARM single board computer: USB, Serial, and Ethernet ports are connected to the ARM single board computer. An interface board is connected to the computer to control the various stepper motors and switches in the tuner.
  • Bar graph Display: Bar graphs display Forward and Reverse Power, a nd SWR .
  • Cooling: Forced air from two blowers Antenna outputs comes standard with 4 x SO 239 high quality Teflon connectors, plus 8 screw posts are used to connect a balanced load open wire, ladder line or twin lead to the tuner. Antenna selection Internal 5 port , computer controlled antenna switch .
  • Calibrated Wattmeter: The Bruene type wattmeter accurately simultaneously measures both forward and reverse power and displays this information on the easy to read bar graph meters on the front panel. It also uses the information to simultaneously monitor the gain of the amplifier.
  • Power: 85 to 260 VAC, 50 60 Hz, selection Automatic. Interface USB and Ethernet. Full remote control capability. Bypass capability 4000 Watts.
  • Shipping Weight: approximately 80 Lbs
  • Product Size: 17.5″ wide, 7.5″ high including feet, 23.5″ deep including connectors, the deepest of which are the two balanced porcelain standoffs. These are approximate numbers but very close. The one that we are not exactly positive about is the depth because of insulator choice.
  • Purchasing an Alpha 4040: The price of the Alpha 4040 will be announced when the product is available.  Please send email to to get on the list.

2 Replies to “Alpha 4040 Automatic Antenna Tuner”

  1. john h ledger

    It sounds to me that you are building a great antenna tuner. Keep up the good work . Iam very concerned about the weight of this unit. I realize you need heavy components to be able to do the thing you need to do inside of this Tuner.

    • Glenn Pladsen

      The 4040 will weigh about 50 pounds.

      We are working on the firmware and still getting bugs cleaned up.

      Glenn AE0Q


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