The results of further experiments were the middle and right model (with two knobs). Originally the design was a three knobs tuner (the left model). The efficiency of the tuner is good, because it can be considered as an auto transformer with inductive and capacitive taps on the coil. Bill Orr, W6SAI, has featured this ATU in the August and September 1993 issues of CQ.Īfter experimentation with various antennas and complex loads, one 5 - 8 µH coil turns out to be the best tuning system for 10 to 80 m. Tom Seed, Z元QQ, has published a basically similar approach with a detailed explanation of the theory of operation in BREAK-IN March 1992. the WARC bands) without the necessity for switching coils and with a minimum of knobs. It is a modified version of the well-known Z-match and is designed as the result of experiments in reducing the SWR on the five HF bands between 3.5 and 28 MHz (incl. In view of the current interest in this approach it seems worth repeating this pioneering 1989 item". PAT Hawker (SK) wrote in Radio Communication: "surprisingly, it seems to have attracted relatively little attention when it featured in TT July 1989. B asically the same features of the current internal automatic antenna tuners. This ATU, I call my design FRI-Match, has been devised in 1972 as an unbalanced tuner for improving the SWR at the transmitter end of coaxial feeders to resonant antennas (eg verticals, dipoles, trapped dipoles, G5RVs, Yagis, loopquads etc.). published in RSGB's RadCom 1989 july and Rothammel's Antenna Book).Īntenna tuner for 10 to 80 m, but also suitable for 50 and 70 MHz bands. FRI-Match ATU, a single-coil Z-Match type:
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