What material works best as a CORE for a small coil at about 500 hertz?
I am building a small coil with 1000 turns of 36 gauge wire wound around it. A 12 volt/ 500 hertz squarewave will feed the coil. I want to receive this 500 hertz tone a few feet away using a sensitive receiver that i have. However, i am having trouble figuring out what kind of CORE to use and where to purchase it. I built several coils using various items such as steel, iron, and ferrite from a flyback transformer. So far, the plain old STEEL works the best, but I keep thinking something else might work better. I searched the internet, but it starts to get really confusing because of all the terminology like "flux density", permeability, field strength, mu, etc etc. It must be something that does not retain magnetism when the coil is de-energized. Any help would be appreciated !