Just some more playing around. I surfed to the following page, looking for bandpass filter designs, such as might be used at the input stage of a radio.
I took the 30m version of their filter, and created it in LTSpice, and did an AC analysis. As you can see, it’s not bad:
The only real problem for it is that it has about 6.5db of insertion loss: all signals are attenuated by this, even signals in the pass band. I haven’t quite figured out how to model the version of the same filter which has a transformer at each end yet. I’m also unsure how the Q of the inductors will enter into the evaluation of the filter. More later.
Mark,
For some interesting circuits with expected performance, check out:
http://www.wa4dsy.net/robot/bandpass-filter-calc
and
http://www.captain.at/electronics/active-filter/
Eldon – WA0UWH
BTW, I enjoy your screencases and online learning adventures – keep it up.
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