This one is pretty simple and the idea has been around for a while (see the “St. Louis Switcher”). The idea is to take an ATX form factor power supply (available for free from dead computers everywhere), hack off some wires, add about $5 worth of parts from the electronics store (like MCM Electronics) or the junk bin and end up with a bench power supply that has enough power to run many mobile transceivers as base stations.
To build the power supply, you’ll need:
At a recent hamfest, Chris KK4RZH gave us some info on a handy gadget to make an ATX PSU conversion even easier: A breakout board that plugs directly to the motherboard header pigtail to eliminate the need to all of the cutting, soldering, etc. It should be noted that these breakout boards likely will not supply the current needed to operate a mobile ham radio transceiver. However, they should work fine to charge batteries, operate QRP or other applications which use lower current. Check out the breakout board here.