Today I finished the bandpass filter.The bandpass filter is a very importand part of the build, because we only want the frequency between 14.000Mhz and 14.350Mhz through the bandpass filter.All the other frequency`s must be blocked.Because I use a IF of 10Mhz and a VFO that can generate between 4.000Mhz and 4.350Mhz,I can cover the whole 20 meter band as I add the VFO frequency to the IF.But it is not that simple.We also have to substract the VFO from the IF frequency.That means that 10.000Mhz - (4.000Mhz-4.350Mhz) = ~ 6Mhz.We don`t want that frequency and other frequency`s pass the bandfilter.I`ve add the filter to the already completed stages of my Bitx20.As I tuned this Bitx20 to the same frequency on one of my other Bitx,I could hear myself when I give a shout in the microphone.Not bad for now.Just two more stages to go,first the PA-driver and after that the VFO.The VFO on the last picture below is the one from my earlyer build Bitx20.
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