Re: Modifying Bitx40 BPF band pass filter

Fokko PH0KKO
 

Final update: I restored the resistor values to their original sate and instead added an amp stage (half of Bitx bidirectional amp) and that gave me a much stronger (+15 dB) and more stable DDS/VFO signal. Instead of adding windings to the toroids in the BPF I increased the the capacitance of the 3 tuned circuits in the BPF to 125 pF (instead of the 100 pF in the original design) and that placed the 7.000 to 7.200 exactly in the peak of the filter. It was a matter of trial and error but got it working.

BPF is perfect now. Thanks all!

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