Double L match unit for open wire or ladder line feeders
I have been meaning to build this matching unit for some time, really just an update on my original matching unit that was really too big for my small shack.
Click on the image for a PDF version.
This is a photo of the inside of the box. Note the copper foil tape on the inside and also inside the lid of the box, I found with the antenna disconnected noise was getting into the matching unit from the outside, this completely cured it.
This the updated design using larger cores with thicker wire to reduce resistive losses.
This is a picture of the outside.
This is the truth table for the diode switching it indicates the combination of relays and inductances to make up the various combinations of inductance.
I didn't use a PCB for the main board or capacitor boards, because the layout was so simple I just used point to point wiring, I did make a PCB layout which came in handy when I was wiring up the whole lot, it proved quite a simple way of doing it. Click on the image to see the PDF.
