Saturday: I've just wound my first coil and built a transistor oscillator and 1 stage clipping amplifier.

The coil is one of my salvaged "mystery coils". The picture below shows the ferrite choke before wrapping (top) and after wrapping. Nowhere near enough winds, but just it's just to test the concept for now. Core is not likely the correct material anyway:

The theory was that it's kind of like a toroid core when conceptualized magnetically, the thinking being that the drive winding is wired through the center of the core.

Here's the breadboarded driver for it:

Tried varying the resistors and although I got oscillation, the results were not stellar. Frequency changes when a large magnet is held very close to the coil, but although it works, it's just not sensitive enough to be useful. Abandoning to more conventional coil designs.