The standard ferrite antenna loopstick for a 365 pF tuning capacitor has an inductance of about 230 microhenrys. This in combination with the tuning capacitor tunes across the full AM broadcast band.
It’s useful to be able to wind your own inductor so it can be used for an antenna coil, a trap to attenuate a strong AM station or as an oscillator coil for a transmitter for the AM band.
The coil form is a standard pill bottle with a diameter of 32mm or 1.26 inches. The wire I used was 30 AWG enameled magnet wire. I close wound the wire onto the pill bottle until the distance the wire covered was 25mm or 1 inch. I held the beginning and end wires in place with black electrical tape. I tinned the wire ends and measured the inductance as 240 microhenrys. That’s just the right amount for the 365 pF tuning capacitor. If it’s a bit too high a few turns can be removed.