It is possible to upcycle an inexpensive / free e-waste XBox 360 power supply into a relatively high quality mid capacity power supply.

Positives:

• Free/cheap
• Seem to be low RF noise
• Great for up to around 50W RF
• There's a 5V 1A output to be had, which is fine for some light-duty Raspberry Pi-ing.

Caveats:

• They're good to about 15A, so won't do 100W, where you generally need around 22A
• They're 12.0V, which is 13% below 13.8V, which might be out of spec for some radios. Check the manual.
• There are a few models around so YMMV a bit on the wiring.

1. Chop off the plug. (Some people have chosen to disassemble rather than chop which might let you keep the ferrite.)
2. Connect the red and blue wires together
3. Join the three yellow wires to the positive side of your chosen power connector
4. Join the three black wires to the negative side of your connector

This might vary a bit depending on variant. Hopefully others can add their experiences to this page.