Harmonics 2

I have changed the lowpass filter. It is a half wave filter. Which means Xc = Xl =50 Ohm. I have used trimmers instead of fixed values.
Calculated values are:
Fc -3db = 178 MHz
C1 17p
L1 45nH
C2 34p
L1 has 3 turns, diameter 8 mm, length = 9 mm
I used 2 of those 5 pole filters.

I have used a 9 pole filter. The supression of harmoinics is much better now. It may not be enough though. Especially the third harmonic at 435 MHz seems to be too strong. The output and efficiency of the PA have increased whith this new filter.

So I think the spectrum analyzer gets overloaded. While alligning the harmonics change but the 145 MHz signal stays the same. I'll change the attenuator to get a lower level. That should help.

My handheld shows the same bad suppression of harmonics. That is another reason I think that the spectrum analyzer is overloaded.

I bought an step attenuator at ebay. It would be usefull for this measurement. Unfortuately it has not arrived yet.