Figure 2: The extra harmonic filter is ready for action in this photo.
I’d used a kit for the PA output LPF in the TX box, but when I added an additional filter between the Progrock and the BS170 driver, I just put it on perf board.
I also cobbled together a little coffin for the filter. using double sided copper clad board pieces, and a lot of solder. Note the solder does the most good when it’s used on the inside seams, where there is copper-to-copper contact.