A project log for PolyMorph Receiver

A minimalist direct conversion radio receiver. 4 general purpose transistors and a Polyakov 2 diode mixer.

morphmorph 03/10/2015 at 15:410 Comments


Uploaded modified schematic. There was a 100k resistor missing on the vfo transistors base. Without it the the vfo doesn't oscillate. The 1n4148 diodes seem to like a 1-1.2 peak to peak oscillator voltage for optimal performance. Currently I have a 4.7uH inductor as the vfo tank and a 1.5uH antenna tuning/impedance matching inductor next neck on neck with it (this is one of the places where the magic happens). The 120p antenna capacitor should be reduced to something like 20p to avoid hum/motorboating in the audio chain. especially when you use external speakers. Keep the audio transistor emitter connection AS SHORT AS POSSIBLE to ground. I'll put a demo video on youtube.