brainwagon

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.

Bandpass Filters.

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.