Today I added a couple of 7/16″ chassis connectors to the 20m LP filter and did the fine tuning of the filter and I got very happy about the result. I managed to get less than 0.1dB attenuation in the passband which was one optimistic goal and I got -75dB attenuation in the notch which is at 28.2 MHz. It’s about -57dB on 28.0 MHz and -55dB on 28.5 MHz.
So now I will try this for a while and if it works fine I will build one for 160,80 and 40m as well. But I need some 7/16″ female chassis connectors, so if you have any lying around please contact me!
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