ATU-100 Antenna Tuner


Recently I purchased a ATU-100 Antenna tuner kit from Aliexpress.

I have purchased this kit because the internal tuner of my IC-7610 has a tuning limit of 150ohms / SWR <3:1 as most internal tuners do.
My previous IC-7300 had the tuner modification which extended the tuning limit, so tuning my antenna was no proplem with this radio.
Since I am using a G5RV Junior antenna in a somewhat inverted V configuration the Impedance of this antenna is somewhat higher on specific parts of each band.
Therefore the internal tuner of the 7610 is not sufficient enough.

Then I found a nice little ATU Kit on Aliexpress, the ATU-100, designed by N7DDC

The kit version just costs me 28 Euro’s including shipping to the NL!!! That it is almost too good to be true you should think.


They are available in various variants:

  • As a kit, all components still need to be soldered. Except the SMD parts, These where already installed.
  • PCB is already completely soldered, all components are already installed. You only have to place it in a enclosure.
  • As a completely built ready to go unit in enclosure.

My preference was for a kit version. This is because I had bad experiences with the cores themselves with all kits I ever ordered from china that contained toroids.

And I was right again.

At the time of ordering the kit, I had already ordered genuine Amidon toroid cores from a reliable local supplier.

The supplied cores are nowhere near the Q factor and AL value for a T68-2 core.
Resulting in very off values of induction.

After winding all cores with the original Amidon cores.. all induction values where spot on with the given windings.
Maybe L3 could use an extra winding to get a better result getting at 450nH. So in my case a total of 9 windings on L3.
The other cores have their windings as given in the manual.


Operating the tuner is easy, I have flashed the latest firmware (v3.1 at the time) so I could use 2 extra buttons for Bypass and Autotune.
Simple press and hold the tune button until “TUNE” is visible on the display, then key the radio with approx 10-15W CW carrier and the tuner will start tuning.
Tuning is very fast, Even a bit faster then the internal tuner of the radio.
I directly could see that the Tuning range of this little tuner is much broader the the internal tuner of the icom.
I can now tune to every part of 40/20/10m.



Reading for SWR are Pretty good compared to the internal SWR measuring in my IC-7610.


This is a bit different, at the lower bands < 40m. Power readout is pretty spot on. but getting more and more into the higher bands the Power reading is getting less and less accurate.
I think this has to do with the detection diodes in the SWR/Power circuitry. I am going to change these out for other ones later on.


Stil to do:

  • I have ordered a small pcb, so I can connect the ICOM tuner socket directly to the tuner.
    And use the tuner button on the radio.
  • Replacing the SWR Bridge diodes for better ones.
  • Finding a nice enclosure for final build.


  • Is this kit value for your money?!, Absolutely the tuner performs just as good as any other small auto tuner like MFJ or LDG’s.
  • Directly order 6x Genuine T68-2 Amidon cores when purchasing this kit or the complete build one, and replace them!


Kit assembled and ready for testing!

First tests look very promising 🙂


Flashed with latest firmware, And folded a proper test jig to test all it’s functionality.

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