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I did CW AM transceiver ladder crystal filter. This project is on my other page. But I was dissatisfied with this project (see Fig.1)!

300 Hz narrowband filter is good for 7M Hz CW. It filters the noise in a crowded band. But when I rebuild, the signals A and b (Fig.1) I heard with equal force. I think that one pic in the filter is better than the broadband filter. For the same reason, the broadband filter is not very good for an AM receiver.

Fig.2! This ladder filter. In this filter capacitors are replaced by resistors.

The lower the resistor values - the narrower the bandwidth of the filter. But in any case, such a filter has one peak in its frequency response. I want to use this property in their next projects.

Experimentally obtained frequency response of the filter.

Author: Kazuhiro Sunamura, JF1OZL, Japan, translation of Nikolai Bolshakov, RA3TOX, rf.atnn.ru