active notch or CW filter

H. Pietzko a very narrow bandwidth). An add-on extra for the existing inexpensive set could therefore prove very useful, particularly if a (much) more expensive one is not available (or the funds thereof). The filter described here is an active equivalent for an LC tuned circuit and can be operated in the parallel mode (peaking function) or the series mode (notch function) as can be seen from figure 1. The filter is connected to the audio output of the receiver or, if present, the tape recorder output. The rive a pair of output of the filter is sufficient to d impedance is active notch or CV/ filter their In general, the majority of low-cost shortwave receivers have poor selectivity. Usually, reception is accompanied by a number of interfering signals, or more than one transmission is heard awl time (especially with CW transmissionsich have headphones directly, provided 600 St or greater. The simulated inductor consists of the circuitry around opamps A2 and A3 (see figure 2). A 12...