Recently built an ATU-100 auto antenna tuner purchased from AliExpress (which means low prices, questionable product, and two months shipping times). I have been largely pleasantly surprised with this tuner, despite the directions being somewhat subpar. It is a ubiquitous enough kit that there are many web posts detailing various aspects of the build, the hardest part for me was air coil inductors. I’ve wound a lot of ferrite inductors over the years but this was the first time I’ve had to build air coils, and to a very specific diameter. What I’ve done with this one was to use Allen wrenches to get the winding size right.
The tuner itself is pretty easy to operate, has a convenient bypass option, and can tune on demand or automatically if it detects the SWR going too high. One caveat though, do not use this with radios that have brittle finals (looking at you, FT100 and FT857) unless you lower power significantly. during the tuning process it will run through a lot of relay switching and show your radio some wildly high SWR before it zeros in.

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Filed under: Kit Building - @ November 29, 2022 9:15 pm