Hello Nate,
I have built 5 QDX and repaired a few others.? My experience would agree with Ryuji on L12 but differ on the LPF toroids.? Here is a picture of the first QDX that I built (and repaired multiple times):
The reason for the picture is to show the adjustment to L4.? I got to this arrangement by balancing the power out between 20 and 30 meters.? When the windings were evenly spaced, I had high power on 30 and low power on 20.? With this arrangement, they are about equal at about 4 watts.
Hans has a YouTube video on what he does to adjust the LPF for the QCX series of transceivers.? You can ignore adjusting the "resonant" coil as the QDX is a class D and not a class E amp, where an inductor is used to tune the output stage.? Otherwise, it is the following process to adjust the LPF for the best output between the two bands shared by the LPF.? Note that the QCX uses three inductors in the LPF vs only two in the QDX.? The process is still similar.
73
Evan
AC9TU
