maandag 6 oktober 2014

lowpass filter

The transverter works but the the lowpass filters are a problem.
I will need to make them myself. 

The attenuation on the second harmonic is just about acceptable on most bands (-40db). on  some bands it less (35db).  I think I understand the reason why.
It was intended for a amplifier that uses a push pull configuration. The second harmonic is suppressed much more. in such a amplifier. I am using a class B amplifier that has a strong 2nd harmonic.

Input Impedances don't seem to be 50 Ohm for all bands. Fortunately I was able to tune it a bit by adding capacitors. That even improved the 2nd harmonic suppression.




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