On 21/06/2013 14:33, cecco.delprete wrote:
I notice that on 20m the power output drops dramatically (~50%).
Hi Francesco
I noted a drop in power after 10MHz in my tests but didn't worry about it, not 50% at 14MHz but a full drop 50% at 18MHz which the rises to give more power on 28MHz. It is a simple design, not optimised for any band, QRP, and after all its only a 3dB drop.
Necessary fine-tune the LP filter?
I don't think you do do anything to optimise the LPF.
Or are other problems: eg. DDS-VFO?
Have you got results above 14MHz, adjustment of the blue Mark Space adjustment pot is quite critical, I find adjusting for max RF power out to the antenna on 28MHz is as good as anything.
73 Eddie
