Original hand drawn ckt, Later on it is redrawn. See, the end of this post.
This was developed with intention of testing 4 Mhz IF of Superhet Receiver design. I check the 4 mhz DSB modulators signal and CW tone of 4 Mhz oscillators . Using Xtal of 3.579 Mhz or any 80 meter band xtal and changig input tuned ckt of band pass filter (capacitor values) it can be used in the 80 Meter ham band.
In the earlier ckt diagram there was some mistake in showing 9th pin of audio ic (actually it is 8pin DIL package !). Now, it has been corrected and uploaded. pin 6 of ta7358 has load resitor of 1k.
Nb i was not able to use it as IF in my superhet receiver project design. I need to change input bandpass filter for IF. As for 4 mhz cw, direct conversion receiver this is good.