Project: KI6J SOTA Tuner

As I have written I am building up my QRP and SOTA arsenal, focusing on portability, efficiency and weight. While weight and portability are obviously desirous for  your primary station configuration, I like to have some redundancy in case Plan A doesn't work. For example, I prefer resonant antenna's, but resonance in a given configuration in the backyard may not always equal resonance in the configuration you end up with in the field. So, I like antenna options.

With that in mind and a need to build something I opted for the KI6J SOTA Tuner as part of my back up antenna system. I haven't built anything in a few years and wanted to get back in the groove on melting a little solder, so I ordered the kit from Stu. Relatively speaking it is an easy kit to build. You do get the pleasure of winding a small transformer and toroid. However if that scares you as a new builder this is a great kit to learn on.

This kit is designed for use by portable QRP operations needing a lightweight, easy to deploy antenna system. Using this tuner, a portable station needs no ground radials and little or no feed line to achieve excellent results. The tuner matches the impedance of end fed, half wavelength (EFHW) wires on 40m -15m and contains a built in SWR indicator. The tuner is designed for durability and reliability of operation and handles QRP power levels, 5W CW and 10W PEP SSB.


The build went very smoothly and when I finished, it didn't work. Wait a minute this is an easy kit, no solder bridges, correct number of turns on the toroid, continuity in the circuit, what could be the problem? So here is a lesson, always read the addendum or errata, or whatever the kit designer calls it, that amends the original building instructions. My problem, I soldered the LED in backwards, which was clearly explained in the addendum that I failed to read. So, I reversed the LED and the unit worked like a charm.

SOTA Tuner
Not a bad Toroid

So, to the field test. I found a piece of wire, roughly 1/2 wave on 20m and put it up on my Jacktite mast and hooked it up to the SOTA tuner. I found resonance on  40m -15m just as advertised. I love when a plan comes together, especially when the plan includes something that I built myself.

Needless to say , I recommend this kit and Stu supports it very well, by asking questions like, "did you put the LED in backwards?" Plan B is now ready to go.

The kit is available at: 

Mike Crownover, AD5A, is a regular contributor to and writes from Texas, USA. Contact him at [email protected].

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