I am trying to understand toroid transformers. I know what transformers do, but I can't seem tro grasp how to say for example do do X I need to have Z bifiliar turns on a Y core. Like I am lookng at a schematic, and it has a transformer that has 2 bilifilier turns of #30 wire on a BN-43-2402 core. What is the mothod behind designing this, or is there some sore of calculator out there that will give you this information?? I am looking to do some home brewing, but I need to understand this first. Maybe someone can point me to a good reference book.