After success with the 40m filter I moved on to the 20m filter.
Again, I adopted some different capacitor combination than presented in the original article.
C1, C3 and C5 are now all 50 pF being a simple series of two 100 pF capacitors each. C2 and C4 are each 320 pF made of 100 pF in parallel with 220 pF.
I also tried using stranded wire for two of the coils. I did this as I had the green and yellow wire left over from the mains cable I stripped for the solid wire used in the 40m filter. After winding the coil with stranded wire it was a bit looser than the solid wire so I covered it in PVC insulation tape to keep the windings tidy.
At first the insertion loss was about 3 dB at 14.100 MHz and got better the higher up the band I went.
I took one turn off L1 and L3, the ones made from stranded wire, and this brought the insertion loss down to just under 1 dB. I am happy with this.
I’ve also started working on the 80m and have nearly all the chassis preparation completed.
73