I bought two of these ‘roll of wire’ on sale at goldmine-elec.com. They came with the wire ends on the same end of the reel, the start end was sticking out of a hole and standing straight out, and the end of the wire was held to the reel with tape, exactly half way around the reel, diametrically opposite from the start. It was obvious that these were meant to be inserted into a circuit board.
I measured both of them with my LC meter, and both measured about 0.93 millihenrys. My meter tends to be off a bit in the millihenry ranges, so I will round off these to 1 millihenry each.
The core of these inductors is air, which cannot saturate like a ferrite or other magnetic core. This type of inductor is most often used for crossover netwotks for speakers. Since a speaker may have to handle high power, tens of watts or more, the crossover network’s inductors must be able to handle high power, using heavy wire and an air core to prevent saturation. So I believe these ‘coils of wire’ were originally made for a speaker crossover network.
