Notch to BPF conversion
Designed by sv3ora

Here is a simple method in which a notch filter can be converted to a BPF using the phasing inversion method. I do not know why one would want to do it like this, but in theory it should have some interesting properties. It should in theory have zero insertion loss (depended on the loss and flatness of the active circuits and the phasing process however). It is also different in the sense that the out of notch frequencies are completely canceled at the end, not just attenuated as in the case of a peaking filter. Notch filters can be easily made with a series shunt LC, with the variable C grounded, so no hands effects or insulation from the chassis is required. They can be bypassed on TX with a single spst switch. They can be easily cascaded without affecting the insertion loss in the pass-band. Another advantage is that with the flip of the switch, one can have both a BPF and a NOTCH without extra LC circuits.

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