A minimalist direct conversion radio receiver. 3 general purpose transistors and a Polyakov 2 diode mixer.
I added some pictures of just the colpitts oscillator of the circuit. In the picture the BJT is 2n3904 and it's collector resistor is 470 ohm, base to voltage supply rail is 150k ohm. 100 ohm and 100k ohm will work respectively. The supply voltage is 5v.
One of the goals of this project has been accomplished, I'm now a licensed radio amateur! I got my license over a year ago and have a lot of fun on the HF bands. My current DX record is a contact to Suriname from Finland, ~9000 km on the 15m band with an 13.5 m end fed antenna a 9:1 unun and only 10 watts. My rig is an 'old' Kenwood TS-50, but it works like a charm. Timing is key on the air and so is chasing your dreams!
Added another common emitter amp, this time for incoming RF.
The performance boost is immense, small signals are much easier to hear and large ones boom (CW and SSB).
Unwanted outward RF leakage seems to have been greatly reduced.
I use an atennuator pot to better hear stations, diminish AM breakthrough and generally control audio volume.
Updated schematic and pictures coming soon!
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.