Coil Forms - Crystal Radio

thingiverse

I created a couple of coil forms for my crystal radios. The forms titled Basket Form V4 and Spider Form v2 allow you to wind the coils directly onto the forms. I've used wire as thick as 20 AWG magnet wire and as small as 30 AWG with 22 AWG kind of being the sweet spot. With the basket coil form be careful not to over tension the wire as you wrap it because the form can slightly warp over time. With the spider coil wrap as tight as you like. The last form, called Basket coil mount, I used when I built the basket coil on a separate board and used this to hold it. Lastly, I used various different calculators to predict the inductance of the coils and regardless of how I built the coil whether on these forms or standalone my inductance always seemed to be higher than expected and I had to trim wire to bring it down. Most likely it was an ID10T error when entering the calculations.