Building your own toroid core and RF transformers

A lot of electronic construction projects intended for hobbyists and amateur radio operators call for inductors or radio frequency (RF) transformers wound on toroidal cores. A toroid is a doughnut shaped object, i.e. a short, flat cylinder (often with rounded edgesJ that has a hole in the centre. The toroidal shape is desirable for inductors ferrites. These graups are further subdivided as discussed below.