I'm replicating the 40m LPF on a breadboard mock up. I want to see the response of this filter with my NanoVNA and tracking generator so I made 3 coils, L1 - L3, and adjusted their inductance to meet the exact specifications from the manual. Caps C25 - C28 are no problem. The output impedance on the coax side I'm putting in a 50 resistor load. But to simulate the input impedance from the PA section I have no idea of what to use for this impedance or whether or not it will make much of a difference to the filter response. Since the circuit is symmetrical maybe 50 ohms there also is OK?
syd/wt1v
N3MNT