so ive been wanting to do this for a while and finally sat down last weekend and threw together a basic crystal set using a 365pf variable cap i had in the junk box, some 26awg wire wound on a pvc pipe for the coil, and a 1N34A germanium diode. antenna is just about 30 feet of wire strung out the window to a tree.

it actually picks up one strong AM station pretty clearly which i was not expecting honestly, figured id get nothing. but ive been messing with the coil tap position and i cant seem to get much else. i know the selectivity on these things is terrible but should i be hearing more than just the one dominant local station? im wondering if my coil inductance is way off or maybe my ground connection is garbage, its just going to the center screw of an outlet cover plate.

also the diode gets warm which seems weird for something with no power supply. is that normal or did i wire something wrong

the outlet screw ground is probably hurting you a lot. if you can run a wire outside to an actual ground rod or even clip to a cold water pipe that'll make a big difference. i built one of these years ago and the difference between a real ground and a floating one was night and day, went from one station to four or five audible ones just by fixing that.

the diode warming up is a bit odd yeah, shouldn't really get warm at all. double check you dont have it wired backwards or touching something it shouldn't, though honestly a germanium diode is pretty hard to kill. also what's your coil dimensions, like how many turns and what diameter pipe? that'll help figure out if your inductance is in the right ballpark for the AM band.

selectivity on crystal sets is just kind of terrible by nature, especially if you have a strong local blowtorch station nearby. some guys add a second tuned circuit before the detector to help reject the adjacent stuff but it gets complicated fast. i built one a couple years back and basically gave up trying to pull in weak stations because my local 50kw guy just washed everything out. ended up putting a little pi attenuator before the detector when i was near the antenna connection and that actually helped a bit weirdly enough.