A Tracking CW pitch audio bandpass filter using 2 SDR modules from AD5DZ: BandPass Filter & LO-MIXER

[Chuck aa0hw]

RECRI KEYER sdr modules from AD5DZ:

https://github.com/recri/keyer

SETUP:

a square wave from a TCL555 655 hertz oscillator is being keyed by FLdidi's serial port RTS PIN feature.... the 655hz SQUARE WAVE goes to the input of the sound card...MIC INPUT jack... from the sound card input it goes to the 1st SDR module "FILT" FILT converts the 655hz HARSH SQUARE WAVE into a 655 hz PURE SINE WAVE with raised cosine edges....and sends it to the input of the LO-MIXER MODULE...the mixer module can be adjusted to any CW PITCH and still keep the bandpass CENTER of the pitch and 'width' of the filter, exactly the same no matter the FREQUENCY being set by the LO-MIXER