My portable Z-match
For portable operations, I was looking for a multiband compact Tuner able to tune both symetrical and coaxial feeders and that would be easy to build. After many searchs on the Web, I finally found few Web pages about the Z-match design (see my "Links" page for some usefull sites and for the schematics).
The nice thing about this Z-match tuner is that it covers all HF bands with only two controls (Load and Tune) with only two variable capacitor without the need of variable inductance control.
The two variable capacitors are comming from old BCLs and the main core is a T-200. The switch of the rear face allows to select either the balanced output or the symetrical one.
Additionally, I have incorporated a SWR bridge. This very simple circuit is lighting a LED when the bridge is not in equilibrium. In one leg of the bridge is the load of the antenna (through the tuner) and in another leg, there is a 50 ohms load. When the tuner is well tuned versus a given antenna, the load reaches 50 ohms, the bridge is at the equilibrium and the LED turns off. Very simple system but it can only work for very low power, otherwise the ferrite core, the diode and the load may vanish in great smoke !
The final result is a compact tuner that covers 80 to 10 meters bands (I never tried it on 160m) and can handle 100W SSB. Tuning can be very narrow for some antenna/bands configurations, particularly with random long wire but in most situations, it will tune fine anyway.
If you have never tried this type of tuner, I encourage you to test it or, at least, review what other Ham fellows have already built and make you an idea of how simple this design is and how easy it is to build. See my links page for more information, knowing this is far from being comprehensive as there are many more available sites related to Z-match tuners on the Web.
