While working on my intended LPFs I've also looked briefly at an LPF for 80m & 60m. A quick linear simulation using QUCS shows that close to 20dB attenuation at 7MHz might be possible for 0.6dB insertion loss at 5.45MHz. (Circuit attached). This might be worth more effort.
But of course it is just a linear simulation, and the QUCS response plots assume a 50ohm Thevenin source impedance. In practice an RF PA output stage isn't a 50ohm source impedance. So the real response is going to be different. So what's the best way to model the QMX RF PA output in order that (theoretical) harmonic levels at the filter output can be calculated?
