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. The ferrite cores are 43 grade cores, I had a lot of them so they were slid over the coaxial cable as a choke, they are probably not needed but I had them spare so my as well put them to good use.


The variable capacitors are receiving type, they are arranged in series so that doubles the voltage handling and halves the capacitance and maintains the balance of the system because it's just the rotary vanes that couple them together. The same applies to the input variable capacitor.


This is a picture of the outside, not very pretty, but I am the only one that's looking at it. I will get around to tidying it up sometime.

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.


          



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