High power 20m LP filter

The LP filter I built earlier for 200w was today built for high power instead. It was a real mess, its hard to bend these copper pipes to fine tune the things and after some problems with the network analyzer I managed to get something that looked pretty good, but it took me hours. It takes a long time to solder one of those coils to the copper, so that is what is the biggest problem and of course after you have un-soldered it the thing is really warm.

Anyway, I managed to get 0.1dB insertion loss and about -65dB notch BUT when I was fine tuning the notch I managed to break one of the 220pF capacitors, and of course I did not have anyone left. I had lots of 150pF and lots of 330pF but nothing between and I did not want to redo the layout and use some other values in parallel. So I ended up ordering 18 pcs of 220pF capacitors from an Ukrainian.

Here are some pictures, now I need to make one for 80m too. On 40m the current hybrid low pass filter works really well, but the one I did for 80m did not work well at all so I am gonna make a similar HP filter as the one previously made.

  1. You should put middle coil at 90 degrees to reduce inductive coupling! I guess you are computer engineer 🙂

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