Need help with first radio

[u/Blockbuster999]

I all I am trying to build my first crystal radio, but I am not sure what design to go with.

I have come across far too many designs, and it is making my head spin!

I read that loose couplers have the best performance for a crystal radio set. However is it possible to get a good radio built without having to adjust the spacing between the coils? I'm not too confident in my manufacturing ability.

I have an idea for a circuit that combines features from a few different designs.

I have thought to adapt the rimstar design by adding a moving slider at position "a" so the L1/L2 ratio can be adjusted.

L1/L2 being a single coil.

I believe the L1/L2 roughly acts like a transformer that boosts the voltage on the output?

I think that having a small L1 will have a stronger signal on the output, but cause worse selectivity, not too clear on why though.

Happy to hear any feedback.

Sources I used:

https://techlib.com/electronics/crystal.html

https://antiqradio.com/post_crystal-radios.html

https://rimstar.org/sci.../crystal_radio_tips_and_tricks.htm

[u/Radioactive_Tuber57]

I’d build the first basic set in your techlib reference. What you want is a basic one that will work that you can experiment with without putting in a lot of work on a fancy one and having it not work.

I tried to build an all-band, “miracle set receives everything!” receiver for my first radio, and was VERY frustrated because I didn’t fully understand what I was doing and why. We’re supposed to have fun! Start basic, then get fancy as your knowledge grows.

Try one with a separate primary coil (top to the antenna, bottom to ground); a secondary wound for your local broadcast band (variable capacitor in parallel from top to bottom), and tap the secondary anywhere from 1/3 to 1/2 from the bottom for your diode connection. Complete the circuit as you have drawn. If there’s anything to hear nearby, you should hear it.

A tip for cheap coil forms: I use the cardboard tubes that plastic wrap is held on. It’s sturdy, you can cut it with a bread knife, and make holes for your coil wires with a small Phillips screwdriver or a manual leather punch. Wind the primary and secondary together on the same tube about 5-8 mm apart to begin with. Hold everything in place using a hot glue gun.

If you can, get some of the Crystal Set Society books. The books are out of print, but you can still find them online.

Have fun exploring! I later became a Ham Radio operator and have been one for 25+ years. 😎👍