ATU-100 – Antenna Tuner

As an alternative for an HF radio that does not have an internal automatic antenna tuner, I ended up buying this kit on AliExpress. There are several options for sale, from the complete kit with all components to an assembled version in a metal case, ready to use.

Since it is a fully open source and open hardware project, developed by David Fainitski (N7DDC), I went for the kit (pictures below), assembling the electronic components and inductors on the PCB.

The assembly is fairly simple and needs no adjustment at all if done according to the manual that comes with the Chinese kit and the documentation available on GitHub. To house the circuit, I used an aluminum box to avoid any RF radiation.

Several tuning tests were carried out successfully, with only a slight warming of the inductors when operated at 100 W for long periods on FT8. A possible improvement would be to buy toroidal cores from a reliable brand (the Chinese ones that come with the kit do not exactly follow the specifications) or to use air-core inductors.

References

• N7DDC ATU-100 mini and extended boards
• ATU-100 7×7
• ATU-100 / ATU-10 N7DDC Russian, Chinese, American Antenna Tuner Kit and part built
• Building the ATU100 (N7DDC) tuner kit — RadioTabaDorismo (Portuguese)
• Hisonauto ATU 100 (AliExpress)
• ATU 100 Antenna Tuner build details, tests, options, and matching capacity
• ATU 100 tuner AliExpress Brasil 1.8 MHz – 30 MHz Auto Tuner (Portuguese)
• 780 ATU-100 Antenna Tuner Build and Measure (and a story)
• Mods ATU-100 N7DDC for QRP RTX with power lower than 5W (like FT-817)
• ATU-100 Kit N7DDC Auto tuner kit build – Up to 100W SSB
• Building an ATU-100 (N7DDC)