increasing voltage from 4 > 12?

I am trying to install a new power antenna in a 2000 Lexus RX300 - the remote turn on lead in only giving me 4~5 volts and I need 12 for the new antenna. How can I accomplish this? The 4volts was not enough to turn on a relay (wired as a remote turn on thing like on the relay example page on this site).

Any help would be appreciated

Brian

That was the only site I found that explains clearly how a transistor works. In your case you have a low dc signal that you would like to be 12V, there are three leads on the transistor, base,collector, emmitter. There are a bunch of different configurations, but i think the one you might want to use would be the common emitter. The base lead of the transistor would be tied to the small dc voltage, the collector would be tied to the 12V and the emitter would be the common ground between the two. A transistor has a multiplying factor, called beta, meaning that the amount of current that is flowing through the base is multiplied by the beta, could be 100, 200 ,300, you have to check. I dont think you will have to worry about this 2 much, as you are using it as a switch, so it will be either off or on. Depending on the size of the small dc voltage you might have to experiment a bit to get the right resistor combination for your application. So what should happen is, you turn on whatever is supplying the small dc voltage, the current from this flows through the base of the transistor, causing much greater current to be drawn through whatever your load is, then to the collector from the 12v source, and all the current flows out through the emitter.     I dont know how much current is needed, but even if you cant use this to power the antenna, it might be useful to power the trigger on the relay that THINKSTER was talkin about. I'm doin this from memory, so i'm probably gonna get burned fer not knowin what i'm talkin about, but there it is ;-)