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Posted by John Bruce McCreath on September 28, 2023 at 00:02:08.
I tried out a new transmatch circuit this afternoon which seems to work well.
It’s a two control unit, but rather than using a differential capacitor with one
coil as done by Palstar and MFJ, it uses a differential coil and one capacitor.
This configuration also has the benefit of being a low-pass network.By doing it this way, there's no need to isolate the capacitor's rotor from the
chassis, which simplifies construction. The differential coil is simply a roller
inductor, with the roller connected to the stator of the cap and the two ends
connected to the receiver and antenna jacks respectively. With the right choice of components the circuit could be built for whatever
frequency range desired. With a 20 uH. roller inductor and a single 540
pF capacitor, mine tunes from less than 5 up to more than 15 mHz. when
connected to a random wire antenna about 100 feet long. 73, J.B., VE3EAR
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