I built this coil, modeled somewhat after the coil I saw in this Youtube video. It uses 24 AWG solid telephone wire, and the winding color indicates the number of the winding according to the resistor color code: 1 (brown) through 0 (black). The first and last windings are 5 turns each. The windings in between are 10 turns as can be seen in the wiring diagram beside the coil. The core is a TOR-61 core, from allelectronics.com. I’m going to try to mount it on a small piece of wood with a terminal strip.
Inductances:
BRN to BRN (Start) 0.08 mH
BRN to BRN-RED (gives an invalid negative number)
BRN to RED-ORG 0.695 mH
BRN to ORG-YEL 1.96 mH
BRN to YEL-GRN 3.91 mH
BRN to GRN-BLU 6.6 mH
BRN to BLU-VIO 10.1 mH
BRN to VIO-GRY 14.4 mH
BRN to GRY-WHT 19.5 mH
BRN to WHT-BLK 22.5 mH
BRN to BLK (end) 25.2 mH
The accuracy of the meter I used is not so good at the low and high ends of the measurements.