The project descibes to use a FT37-43 toroid. This toroid is manufactured by Amidon. I’m using a similar toroid made by FairRite that has similar specs. I’ve choosen this toroid over the FT37-43 as I could easily buy it at Mouser.com which is not the case for the Amidon toroids. The partnumber of this toroid at Mouser.com is 623-5943000201.
For the wire I’m using 0.4mm enameled copper winding wire. We need about 50 cm of it.
First take about 10 cm of the 0.4 mm enameled copper wire and make a 90° bend. Then take 4 cm and bend in half, twist it together so you end up with 2 cm of twisted wire.
Since the toroid is rather small, I prefer to use some string, to clamp it in a small vise. That way I keep both hands free to wind the wire. Hold the twisted piece of wire against the toroid and pass the short end of the wire through the toroid 5 times. With the long end on the other side, do the same thing, but go through the toroid 20 times.
When you finish winding you should end up with something like the picture below.
And so your second toroid for this project is done too!