I have a band saw welder, but I find that blades joined with silver solder are more reliable.
The silver solder should contain at least 50% silver.
The jig below makes sure that the ends of the blade are held exactly correctly in position.
The blade ends need to be tapered at about 20 degrees to maximise the contact area to be soldered.
The jig is held in a vice. The blade ends are held flat and against an edge which keeps them in line. The blade ends are scarfed at a 20 degree angle. The cap screws are finger tight.
If you look closely you can see the scarf about to be soldered and joined. The edges to be joined are fluxed.
Band saw blade material is bought in 30 meter lengths, often very cheaply on Ebay. Silver soldering requires a gas or oxy torch, a container of flux, and some silver solder (from plumbing or welding suppliers). The technique of silver soldering is quickly learnt (practice on some worn out or broken blades). The blade is cut square with an angle grinder and bevelled on a belt sander. The jig needs to be made but it is simple. I could supply dimensions if requested.