I would like to share my experiment.
After a several month i have fixed output power for my QCX 20M (my kit No.#487)
and now i can getting with full power 5 Watts @12Vdc
before I solve my QCX 20M. I can get output only 1.5 ~ 2w maximum
First i observe LPF circuit C25 and C26 (390pf) getting very hot during transmission.
This is my modification.
1. remove 1 turn of L1 and L3 (use only 15 turns) --> power improve abit to ~ 2.5w
2. remove C25 and C26 (390pf) and i replace with 2 series of MLCC capacitor 680pf (because there are in my stock) --> this big improve my power to 5w !!!
I believe my issue is mismatch at LPF especially at C25 and C26 (390pf).
thanks group for good knowledge sharing and Hans for the grate kits.
finally soldering in the right place
output power @12vdc