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I use a FRI-match almost exclusively as an asymmetrical tuner for coaxial feed antennas or as a tuning unit between transmitter and a HF amplifier to be tested. If a symmetrical antenna system needs to be adjusted, I use (fig ») it in combination with a suitable balun at the output of the ATU.
My favourite antenna tuner is the single coil Z-Match. I tend to use ladder-line feeder instead of coax, so I believe a tuner designed for balanced feeder is a much better solution than a T-Match or SPC using an external 4:1 balun or similar.
Single Coil Z Match Figure 1 Single Coil Z Match - Circuit Diagram Coils L1 (57 mm diam.) and L2 (67 mm diam.) are wound with around 16SWG gauge enamel wire. The precise gauge is not critical but the heavier the gauge the better the efficiency one might expect from the tuner. The former (figure 2) is made from perspex* sheet and drilled as
A Single Coil Z Match Tuner design using an iron powder toroidal coil has been described. The design achieves a wide load resistance matching range as did the open coil AR Single Coil Z Match. The efficiency is good at 3.5 and 7 MHz but deteriorates at higher frequencies.
A few years ago I assembled a Single coil Z Match which could handle at least the 400 watts of power using two 3 gang capacitors I had on hand. These had a maximum capacitance of 200pf and plate spacing of 0.5mm.
The ATU is a single-coil Z-Match tuner designed by Chuck Carpenter, W5USJ, based on the Z-Match publications of Charlie Lofgren, W6JJZ.** Most notably, the article “An Improved Single-Coil Z-Match” published in the ARRL Antenna Compendium Volume 5.
The Z-Match antenna tuner is again proving popular. This note provides some background on the design, presents an improved "single-coil" version, and describes two tests for checking the performance of any tuner. The Z-Match is built around the multiband tank circuit that came into use around 1950 to
