"john" wrote...
the radio I'm looking at uses 8 amps on am and 15 amps on
ssb, on transmit.
I will wire the thing into the circuit when I get it to the motor home
but I would like to use it with a cigarette lighter plug, in the auto en
route.

I would not take the power from the lighter plug.
I don't know how good they make the plugs in America, but I doubt that they are perfect
connections.
Any poor connections where the contacts meet will give a resistance, which will drop voltage
and create heat. The voltage drop will vary with power output, so your supply to the radio
could be bouncing up and down to your voice on SSB... which may cause warbling or other
distortion.
Apart from any radio problems, you have to consider the heat being created in the socket and,
possibly, in the wires to that socket.


Regards,
Peter.
http://www.citizensband.radiouk.com/