Symmetric (balanced) Pi-Network antenna tuner
Blue Ridge Amateur Radio builds Symmetric (balanced) Pi-network antenna tuners. Symmetric tuners have a reputation for being the most efficient tuner design. They also happen to be the most expensive tuners, due to the number of components required to build a symmetric tuner. We don't believe that power should be wasted within an antenna tuner, that's why we believe that symmetric tuners are the way to go.
Our ST-1500 Symmetric tuner is specifically designed to be used with open wire line feeders. The connectors on the back only support open wire line output. We believe that open wire tuners and balanced antennas are the foundation of the Amateur Radio hobby, and it is literally where every single ham starts out. Our goal is to make multi-band operation on 1/2 wave or better dipoles, full loops, delta loops, and other balanced wire antennas easy and fun.
The ATU4K Balanced Tuner
The ATU4K is a collaborative effort between www.trueladderline.com and Blue Ridge Amateur Radio. The ATU4K is a broadcast quality, stepper motor controlled, remote antenna tuner.
The ATU4K utilizes a symmetric L-Network with a switching system that allows the capacitance to be moved from the input side of the system to the output side. This mechanism guarantees that an absolute minimum capacitance value can be applied to bands like 10 meters, while the full value of over 2500pf can be applied to low bands like 160 meters.
We have provided a comprehensive write up an efficiency proof here:
For a detailed overview of different tuner types and their relative efficiencies, please see this link:
For now, note that symmetric tuners are available through various vendors today, but they come with a pretty good price tag because they require more components. Our symmetric tuner is at a price point that is less than the average vendor's simple T or L network tuners.
Simple To Operate
Our tuners are easy to operate and contain no additional electronics. We believe that SWR/Watt meters should be things that are external to the tuner for two reasons:
Reduction of stray capacitance
Onboard SWR/Watt meters are generally cheap and inaccurate
Symmetric tuners have 2 roller inductors. The inductors are linked together through a belt drive system.
Capacitors and Drives
Each capacitor is driven by an independent vernier reduction drive transmission.
The 1:1 current balun (RF Choke) is located on the input side of the turner and not the output side. This eliminates the baluns exposure to wild impedances and currents that are present when the balun is placed on the output side of a tuner. This RF choke is used to stop common mode currents from flowing on the transmission line.
Inductor Drive System
In this picture you can see the belt drive, geared RF isolators and the turns counter transmission.
RF input and output
In this view you can see the SO-239 RF input connector as well as the through hole RF insulators for RF output.
Our tuners can come in any color you like. We powder coat all of our tuners, inside and out, to prevent oxidation and to provide the user with a rich color scheme that fits their station design. We get all of our powder coat colors from Prismatic Color (https://www.prismaticpowders.com/) and can use any of the single stage (solid colors) that Prismatic provides. Want a neon pink antenna tuner, you've come to the right place.
Dimensions and Wiring
Our tuners are 10x10x12. 10 inches wide, 10 inches tall and 12 inches deep. The Rollers are stacked on top of the capacitors and separated by a metal mid-plate.
All of the wiring in our tuners is confined to the mid-plate. This means that all of the case work can be removed without having to unsolder or unscrew any of the electrical connections. You'll recognize this as a unique advantage, if you've ever tried to service other antenna tuners.