I ran across an interesting post about a simple AM broadcast regenerative receiver and thought I’d have a go at building it. Here is the original post http://imgur.com/a/JpwJs.
The basic schematic is:
I started with a ferrite rod that I had from an old broken AM receiver.
I wound 60 turns of magnet wire that will form part of the tuned circuit with the variable capacitor. According to the original post, should measure about 240 uH. Mine came out at just under that.
Next, on top of the first coil, wind a 10 turn coil that will couple the signal from the tuned circuit into the RF stage.
The final winding of 5 turns is done on the other side of the ferrite. This is the regeneration coil. It will feed back some of the voltage from the amplification stage causing a huge amplification of the RF signal.
Be careful with the polarity of the coils (check the schematic) I initially wound the coil incorrectly and it took a while to figure out what the problem was.
I built the circuit on a breadboard, just like in the original post, but I used an LM386 circuit for the audio amp stage.
It worked okay, but there were loose connections that caused low and static-y audio. I had a scrap audio amp that I had made for an earlier project that was collecting dust, so I rebuilt the rf stage on the same board as the audio amp.
The receiver works great, I can clearly pick up all of the local AM stations with no trouble. The final schematic for my working version is:
Now, all I need is a suitable enclosure.