Evan -- so in this case, I am *using* the 10meter filter.? ? ?Its knee is at 32-ish MHz and appears to be used for 15 meters as well.? ? At least I hope I am!
These data seem to prove that we have at least a? -28dBc spur (harmonic) being formed due to the conduction of the output diode for the 10m filter!
There are likely OTHER sources, that are responsible for the remaining -34dBc 3rd harmonic.? ? ?Need to get all of this down below -43 dBc.? And for a radio of this advanced design, would be nice to have it significantly more impressive than just meeting requirements.? ?
The material I quoted cited "non linear passive components" -- is it possible that the capacitances of the reverse biased other diodes are also changing in a non-linear manner with instantaneous voltage (because the RF voltage is a varying percentage of the back biasing DC voltage) -- and that THIS is also changing the response in a non-linear manner and introducing harmonics?? ? Seems possible!? ? ?Ashhar wisely included a voltage doubler circuit, but that still means there is a significant percent change in the NET reverse bias on each part of a cycle.? ?What about either replacing the output diodes with RELAYS or using a much much higher reverse voltage?? ? ?
I just don't know exactly what next is the best step.? ? These diodes I don't think are ever switched "under load"? so a relatively modest relay could replace them.? ? at 40 watts, they should see currents only in the 1-2A range (even with 2:1 SWR).? ??
Anyone else made measurements on their V2?? ? Or have ideas?
Gordon KX4Z
