"Tony Hwang" wrote in message
news:GM0ze.1878860$6l.1767733@pd7tw2no...

Hi,
Or if the current draw of the radio is know, installing drop resistor of
correct value and Wattage. Calculate with Ohm's law.
Tony

That will not work because a load like a radio is variable.
But it probably does run off 12 volt batteries, so like the first guy said,
just hook it up to one of them.
Greg