i was wondering if there would be a cheap but effective way to take an ordinary computer power supply and mod it somehow to have an output of 13.8V Thanks
You could try vmodding it. I got a 3.3V line up to 3.75V stable, which is about a 14% increase. If you had the same success (percentage wise) you'd get about 13.6V - so who knows...
It wont run on 12v? I know cars typically have more that 12v, but ist should still work down to 10v or so. Or is this not vehicle CB equipment. How much power do you need? if it is less than 4A or 55.2W http://www.jameco.com/cgi-bin/ncommerce3/ProductDisplay?prmenbr=91&prrfnbr=3589&cgrfnbr=501&ctgys= may be of use to you. $30, but you know it is ment to run at that voltage, Plus you still have warranty so if it goes apesh** and breaks something you can proabaly make them replace it.
if your psu has sense lines on the 12v line, the its real easy look here: http://www.xtremesystems.org/forums/showthread.php?s=&threadid=37574 very well written guide by hell-fire if it doesnt u may have to open up the psu, find out the vreg, and mod it using the feedback circuit like you would with a mobo vmod