It will pull more than 45 amps. And even if it only pulled 45 amps, I would want at least a 60 amp supply for it. You don't want to run a supply that close to maximum all the time or it won't last very long.EX 500V
Output Power with 4 watts input:
250 watts
Aprox. Power Output with 20 watts input/
Aprox. Max Current
500W/45A
4-2SC2879
These transmitters are designed for mobile or base, powered by the 12 volt vehicle battery or 12 volt regulated power supply
http://www.texasstar.com/CWmed.html
Thanks for the info nomadradio...the one I have is regulated and does 12- 16 volts. Should I go up to 75 or 100 to be on safe side?