I think you'd be better off getting one commercially first. Then experiment
with it so you can make your own. It's much less frustrating that way.

Purists insist on using a chunk of galena and a "cat's whisker" for the
detector, but you can substitute a plain old 1N34 germanium diode to
accomplish the same thing without all that trouble of having to poke around
to find a "hot spot" on the chunk of galena.

There are different ways to accomplish tuning. You can have a variable
coil, or a variable capacitor. Big variable caps can still be found, though
not new, and they're easier to work with. Smaller variable caps can be
salvaged from junked transistor radios.

It's been said that "A dollar in the antenna is worth ten in the receiver."
That holds true. String up as much long wire as you can for your antenna.
And also make sure you have a good earth ground. That will really help.

After you get all this done, please let us know what you hear!!!!

Matt J. McCullar, KJ5BA
Arlington, TX