I decided to try building a filter from the W2VJN “Managing Interstation Interference” which is basically two quarter wave open stubs for 20m with an L in the middle, causing a notch filter for 14.2 MHz. This is used on 40m to remove the interference that it currently causes on 20m. The 40m top antenna and top 20m antenna are only about 4-5m apart and caused some problems. However with this filter all the interference went away and the over tone is now just like any other signal on the band. I am extremely impressed by the measurements, which were well over my expectations and I will not throw my home-brew 7-pole LP filter away and use this instead.
0.07dB insertion loss on 40m and -86dB attenuation on 14.2 MHz!
