Thanks to Hans the QCX is an excellent learning platform
To cover three bands ..
With few exceptions I built and aligned a 30m QCX to specks...
1) I did not install LPF on QCX PCB because you will need different LPFs for different bands and Hans has several (to include switchable) QRPLabs options
2) I installed T1 on bottom of PCB for ease of solder/unsolder...ing, turns out no fiddling was required for 40, 30, 20
3) C1 requires fiddling to cover three bands (two bands no problem) and of course must be tweeked each band changeI I have two variable caps on PCB ... Note too the variable caps supplied with kit do not tolerate much heat and/or fiddling I destroied several and ended up using two variable ceramic units
4) I fiddled with L4 enough to determine I needed a better understing of class E amplifier "efficency" so L4 = STET for 30m
Remember too based on much discussion here on the list... different LPFs produce different RF output levels, fiddling with LPFs can be a delightful learning experience
Replacing the onboard audio filter with different designs and bandwiths was an OUTSTANDING learning experience