Reversing the inductor in the Chinese QRP antenna tuner makes all the difference

Like many I was disappointed with the Chinese antenna tuner kit "QRP manual days" back in 2014 and I never really got it to work. 

That was even after I had replaced the two polyvaricon capacitors. The two screws for mounting each of the variable capacitors were too long. The result was that they interfered with the moving plates of the capacitor and I ruined both of them. There was no warning of this in the manual, so beware anyone who buys this kit.

Despite fixing this, it didn't really tune anything. I later learned that it probably works for low bands like 80 m as it is, but I didn't notice that. I thought maybe the toroid core of the inductor was of inferior quality, but never really investigated it, so it sat unused on the shelf for 7-8 years.

QRP Antenna Tuner

My 75 meter horizontal loop antenna is tuned by a home-built Z-match antenna tuner, a slightly modified version of the Norcal BLT (Balanced Line Tuner), with a resistive SWR-bridge using a super-bright LED. I could tune my 75 m loop on all bands up to and including 20 m, but at higher frequencies I could not get the series capacitor small enough. The cure was to add a switch to choose between the original primary coil with 8 + 8 turns or taps at 4 + 4 turns, after an idea by DL8RAM. This is selected by the 80-20/20-10 m switch and comes in addition to the switch between Hi-Z/Lo-Z on the secondary (the output). This tuner also tunes a 13.4 meter doublet well on 40-10 meters.

I designed a frontpanel layout for the tuner. It was generated from a text file using the program of WB8RCR. I would recommend this program for any homebrewer who wants to improve his panel layouts. I print mine on paper,