This is great information!
I have some additional questions about using DIY7 transformers and hope you might know the answers.
1. In a twin DIY7 filter setup such as used in the KN-Q7A and CS-Series, what happens when the coupling capacitor values are decreased or increased? By chance does changing capacitor values shift the entire passband frequency range, or does it only change the passband width? Or both maybe?
2. What happens when the value of the single capacitor located BETWEEN the DIY7's is changed?
3. Are there any modifications you can suggest to better optimize and improve the performance of a CS-15/17 kit if used only on the 15M band?