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I have built this homebrew Antenna Matching Unit in an IBM PS/1 computer chassis. It is symmetrical designed so either connection can serve as input or output. The design is a simple variable lowpass T-filter with input and output inductances that can be changed in four steps. In between there is a capacitor to ground that is continuously varible. The capacitor is made of four heatsinks that is mounted in pairs and two of the heatsinks moves when turning the C knob. There is 28 turns from end to end and the maximum capacitance is approximately 300pF with the heatsinks choosen.
The Heatsink Capacitor
This 2nd homebrew Antenna Matching Unit is also a variable lowpass T-filter. It is more versatile since the inductansce is continuously variable. I planned to use heatsink capacitors in this design also, but I had a suitable variable capacitor in the junk box.
L1 is made of 15m of 1.5mm² solid copper wire, wound on a ceramic core, approximately 100 turns. It used to be a high power wire wound potentiometer (250Ω 250W). The inductance is approximately 40µH. The copper wire is fixed with epoxy.
L2 is made of 36 turns of 1.5mm² stranded copper wire, wound on a piece of plastic pipe with a diameter of 32mm. The inductance is approximately 20µH.
Each section of C1 is 150pF variable and C2 is 100pF.
S1 can add or remove L2 in parallel with one branch of L1, to reduce or increase the inductance.
S2 can add or remove C1A and C2, to increase or reduce the capacitance.
The wire wound 250Ω 250W potentiometer
L2 wound on a 32mm plastic pipe ...
... and fixed on the bottom flange of the box