Recently I've been playing around with JFET transistors, something new for me if I must be honest. Originally I was intending to build a grid (or gate in this case) leak detector using a JFET in place of a tube, but I found that I couldn't get it to work. So after looking at schematics online I instead decided to try using the JFET as an RF amplifier and then feed the output into a crystal detector. That worked surprisingly well, once I figured out how to bias the thing properly! Of course I had to use a piezo earphone to hear anything, but it was much louder than the unamplified crystal sets I had built previously. I then decided to build an audio amp so I could use low impedance headphones in place of the piezo buzzer. The RF amplifier is a 2N5457 JFET and the AF amp is a 2N3906 PNP. I used a 1N34A for the detector diode.
Performance wise it works alright, I'm able to pick up three local stations during the day, including one I can't really hear with an unamplified crystal radio. This is still experimental so I'm using a loopstick I bought at a hamfest (so I'm not really sure what it was originally intended for) with a 200 pF varicap for the tank circut. As a result the band coverage is limited. Now that I know it works though I'm going to make a better tapped coil and use a different varicap with a higher value. Unfortunately my antenna situation is terrible (patch cords hooked up to the metal vent hood over the stove in my apartment) so my reception is limited anyway.
Anyway, I know it's not much, but it's the first amplified radio I've gotten to work well so I'm proud of it. If anyone has any suggestions for improved performance please let me know.